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A urine test can diagnose male chlamydia within an hour, according to the BBC. The sexually transmitted infection, which often has no symptoms, can cause fertility problems and is estimated to be carried by 6.8% of young men in England. This new urine test reportedly enables same-day treatment following a one-hour wait for results.

The well-conducted study behind this story has demonstrated that the Chlamydia Rapid Test is highly accurate in confirming that a man is not infected. It also has a good, but slightly lower, level of accuracy in correctly identifying that a man did have the infection. The technique also avoids using urethral swabs to extract samples from inside the penis.

This quick, accurate test is an important step towards both reducing the growing problem of chlamydia in the young and providing rapid treatment for those affected. It is also hoped that men would be more likely to agree to this type of testing, as they currently get tested less often than women. Further testing in a larger set of samples will probably be needed before this test could be brought into current practice.

 

Where did the story come from?

Elpidio-Cesar Nadala and colleagues of Cambridge University, Barts and the London Charity, and other UK centres, carried out this research. The study was funded by the Wellcome Trust and the National Institute for Health Research’s Cambridge Biomedical Research Centre, and published in the British Medical Journal.

 

What kind of scientific study was this?

This was a diagnostic cohort study assessing the use of a rapid urine test to diagnose and screen for chlamydia infection in men.

The study recruited participants between March and November 2007 from a young people’s sexual health centre, and a genitourinary medicine (GUM) clinic in the UK. They enrolled men aged 16 or over, who had not taken antibiotics in the previous month, and were able to understand the written information forms used in the study. The researchers enrolled 1211 men, who were confidentially interviewed about their symptoms and relevant sexual history.

Each participant gave two urine samples, two hours apart, which were collected using two different methods. The first sample was collected using the new technique being trialled, The Chlamydia Rapid Test. The testing process involved using a centrifuge and adding various ‘reagent’ chemicals that reacted with substances in the urine to separate and identify them. This testing of the first sample was carried out on-site by trained clinic staff.

The second urine sample was divided into two portions. One was sent to the laboratory for testing, using the standard ‘polymerase chain reaction’ (PCR) method, which normally returns results in 7-10 days in a clinical setting. The other half of the sample was frozen and stored in case further testing was necessary.

The rapid urine test was compared to standard testing using four key measures:

• Sensitivity: accurately identifying a positive sample,
• Specificity: accurately identifying a negative sample,
• Positive predictive value: the proportion of people with a positive test result who are correctly diagnosed as positive and
• Negative predictive value: the proportion of people with a negative test result who are correctly diagnosed as negative.

 

What were the results of the study?

Using standard PCR laboratory testing, chlamydia was detected in 4.4% of samples at the sexual health centre (20/454) and in 11.9% of samples at the GUM clinic (90/757). Compared with standard testing, the Chlamydia Rapid Test had:

• a sensitivity of 82.6% (90/109),
• a specificity of 98.5% (1085/1102),
• a positive predictive value of 84.1% (90/107) and
• a negative predictive value of 98.3% (1085/1104), respectively.

The researchers used a DNA test that estimated the number of bugs, (the organism load) in the samples. The organism load in samples that tested positive for chlamydia had a significant correlation with the results of the Chlamydia Rapid Test, i.e. the more bugs that were seen in the sample, the better the accuracy of the test’s results.

 

What interpretations did the researchers draw from these results?

The researcher conclude that using the new Chlamydia Rapid Test with samples of males’ first urination of the day would be an effective diagnostic tool for chlamydia infection in men. They say that the availability of test results within an hour would allow for immediate treatment and contact tracing, potentially reducing the risks of persistent infection and onward transmission.

 

What does the NHS Knowledge Service make of this study?

This well-conducted study has tested the validity of a new rapid urine test for chlamydia in men. The test results demonstrate a high accuracy in correctly confirming that a man did not carry the infection, with both high test specificity and negative predictive value. The technique also had a good, but slightly lower, accuracy in correctly identifying that a man did carry the infection, with test sensitivity and positive predictive values of 82-84%.

The development of this technique is an important step forward in efforts to slow the increasing spread of this harmful, but often undetected, infection among young people. The rapid urine test has the advantage of being a fairly quick and non-invasive test that avoids 7-10 day waits for results, and urethral swabs common with current practices.

The rapid availability of results of this new test offers would potentially enable prompt treatment and contact testing. Currently, women get tested more often than men, and it is hoped that this new method would make men more willing to be tested.

Further testing in a larger number of samples is likely to be required before this test could be brought into current practice. If it were to be used for screening, it will be especially important to consider the staff, training and equipment required, and where the test would be made available.

Links To The Headlines

Rapid chlamydia diagnosis for men. BBC News, July 31 2009

Links To Science

Nadala EC, Goh BT, Magbanua JP, et al. Performance evaluation of a new rapid urine test for chlamydia in men: prospective cohort study. BMJ 2009;339:b2655.

A “new jab could help repair heart damage and prevent future attacks”, reported the Daily Mail. It said that new cells were ‘kick-started’ into growing when researchers injected a protein called neuregulin 1 into the hearts of adult mice and rats. The newspaper reports that further tests of the injection will be needed before it can be used in humans, including tests on larger animals such as pigs.

This animal research has identified a protein that may be useful in treating some heart disease. Although the news reports suggest that neuregulin 1 (NRG1) treatment might reduce the risk of a second heart attack, this possibility has not been tested in this study, which looked specifically at the effects of the treatment on the recovery after a first simulated heart attack in mice.

The results of this study are promising but as the newspaper suggests, more research will be needed to determine the safety and effectiveness of this protein for treating heart damage before it could move on to testing in humans, and this research will take time.

 

Where did the story come from?

This research was carried out by Dr Kevin Bersell and colleagues from the Children’s Hospital Boston and Harvard Medical School. The study was funded by the Department of Cardiology at Children’s Hospital Boston, the Charles Hood Foundation, and the American Heart Association. One of the authors is reported as being the founder of an organisation called CardioHeal but no further details are provided. The study was published in the peer-reviewed scientific journal, Cell.

 

What kind of scientific study was this?

In this study in rats and mice, the researchers investigated whether they could develop a technique to make fully developed adult heart muscle cells divide and form new cells. Such a technique could potentially be used to heal damaged heart muscle, without the need for using stem cells.

The researchers started by trying to identify proteins that could cause fully developed adult heart cells to divide. They were particularly interested in the proteins fibroblast growth factor1 (FGF1), periostin, and neuregulin1 (NRG1). These proteins prompt foetal heart cells to divide and form new cells, and the researchers wanted to see whether the proteins would have the same effect on adult rat heart cells. To do this they grew adult rat cells in the presence of these different proteins and looked at whether the proteins prompted the cells to start making more DNA so that they could divide.

These experiments found that all three proteins prompted adult rat cells in the laboratory to begin making more DNA. As FGF1 and periostin were already known to have this effect, the researchers looked at NRG1 in more detail in a large number of related experiments, some of which are described further here.

Most cells in the body have one nucleus (mononucleate), a structure that contains the majority of genetic material of the cell (DNA). However, some adult heart muscle cells have two nuclei (binucleate) or more (multinucleate). The researchers investigated whether NRG1 prompted cell division in mono- or binucleate heart cells.

The researchers used biochemical methods to see whether the proteins ErbB2 and ErbB4 were needed for NRG1 to have its effects, as they were known to interact with NRG1. They then genetically engineered mice so that they could ‘switch off’ the action of ErbB4 two to four days after the mice were born. These mice had normal heart development up to this point. The researchers looked at the effects that this ‘switching off’ had on the mice’s hearts at 19 days after birth.

The researchers also looked at the effects of injecting NRG1 into three-month-old normal mice. They carried out various tests to see whether any cell division occurred in fully developed (differentiated) adult heart muscle cells rather than undifferentiated progenitor cells.

To look at the effects of NRG1 on damaged hearts, the researchers blocked off one of the coronary arteries on the left side of the heart in two-month-old mice to mimic the effects of a heart attack. One week later, they started injecting some of the mice with NRG1 daily for 12 weeks followed by two weeks without injections, while other mice did not receive any injections (control mice). The researchers then looked at the effects on the structure and function of the heart.

 

What were the results of the study?

The researchers found that the proteins FGF1, periostin and NRG1 prompted adult rat cells in the laboratory to begin the process that leads to cell division. They then showed that NRG1 prompted about 0.6% of the adult rat heart cells to divide in the laboratory, and these cells lived for the entire duration of the experiment (up to 163 hours). All of the cells that divided were originally mononucleate heart cells; some of these heart cells underwent division of their nucleus and became binucleate cells without dividing.

Further experiments showed that NGF1 needed the proteins ErbB2 and ErbB4 to have this effect. If the researchers stopped the ErbB4 protein from working in genetically engineered mice after birth, they found that at day 19 none of the heart muscle cells were dividing, while in normal mice, about 5% of the heart muscle cells were dividing. The hearts of the 19-day-old mice lacking ErbB4 had fewer cells than normal mice.

The researchers found that injecting three-month-old normal mice with NRG1 led to a proportion of heart muscle cells to divide and this process required the ErbB4 protein. There was no evidence of the heart muscle cells dividing in normal mice that had not been injected with NRG1. Tests suggested that NRG1 caused fully developed (differentiated) adult heart muscle cells to divide rather than undifferentiated progenitor cells.

In control mice that were given a simulated heart attack, there was an enlargement of the volume of one of the lower chambers of the heart (the left ventricle), as well as a thickening of the walls of this chamber 15 weeks later. Tests also showed reduced heart function. These changes are similar to those that occur during the development of heart failure after a heart attack in humans. However, mice treated with NRG1 injections for 12 weeks did not show significant enlargement of the left ventricle or thickening of the walls of this chamber, and had improved heart function compared to untreated mice. NRG1-treated mice were also found to have less scarring of the heart muscle compared to the untreated mice at 15 weeks. Tests showed that the treated mice showed more heart muscle cell division than untreated mice.

 

What interpretations did the researchers draw from these results?

The researchers concluded that they have identified “major elements of a new approach to promote [heart muscle] regeneration”. They say that their findings suggest that stimulating fully developed heart muscle cells to divide may be an alternative to stem cell-based approaches to promoting heart muscle regeneration in mammals.

 

What does the NHS Knowledge Service make of this study?

This animal research has identified a protein that may be useful in treating heart disease. Although the news reports suggest that NRG1 treatment might reduce the risk of a second heart attack, this possibility has not been tested in this study, which looked specifically at the effects of the treatment on the recovery after a first simulated heart attack in mice.

The results of this study are promising but more research will be needed to determine the safety and effectiveness of this protein for treating heart damage before it could move on to testing in humans.

Links To The Headlines

‘New way’ to repair heart damage. BBC news, July 24 2009

Daily injections could reverse heart attack damage, scientists claim. The Daily Telegraph, July 24 2009

New jab could help repair heart damage and prevent future attacks. Daily Mail, July 24 2009

 

Links To Science

Bersell K, Arab S, Haring B and Kühn B. Neuregulin1/ErbB4 Signaling Induces Cardiomyocyte Proliferation and Repair of Heart Injury. Cell 2009; 138: 257-270

This page brings together the latest science and developments on the swine flu pandemic into a single accessible resource for both health professionals and the general public.

You will find a range of regularly updated links to scientific resources on the Pandemic (H1N1) 2009 virus listed below. We will also be critically appraising new research on swine flu as it is published.

For the latest, more general news on swine flu in the UK, including prevalence, NHS policy and guidance, go to swine flu latest from the NHS.

We encourage comments and suggestions from the scientific community on the development of this page.

Links

 

Journals and research

• The Lancet H1N1 Flu Resource Centre brings together swine flu related content from over 40 journals and 11 learned societies. Free access to all content.
• Nature includes articles on the history of swine flu and a blog rounding up the latest swine flu news from around the globe.
• The New England Journal of Medicine H1N1 Influenza Center features articles, review papers and surveillance updates of swine flu news.
• The British Medical Journal’s swine flu blog is updated regularly. The site also has a swine flu patient information leaflet and a section on swine flu in BMJ BestPractice.
• The Center for Infectious Disease Research and Policy (CIDRAP). A good resource with the latest news, and a useful overview of the pandemic.
• Eurosurveillance. An open access peer-reviewed journal about infectious diseases surveillance, prevention and control. 

 

UK government

• Health Protection Agency
• Department of Health
• Chief Medical Officer for England 
• Scotland: Health Protection Scotland
• Wales: National Public Health Service
• Northern Ireland: nidirect 

 

International government

• World Health Organization Pandemic (H1N1) 2009
• European Centre for Disease Prevention and Control
• US Centers for Disease Control and Prevention
• US Pandemic Flu.gov
• US National Library of Medicine. Enviro-Health links 2009 H1N1 Flu (Swine Flu) 
• Medline Plus, health information for the US public
• Promed, from the international society for infectious diseases, is a useful electronic global reporting system for emerging infectious diseases

 

Swine flu genetics

• Gene sequencing and related resources. GenBank, National Center for Biotechnology Information
• Database of influenza genomic sequences and related information. BioHealthBase Bioinformatics Resource Center
• Analysis of genetic data for the origin and evolution of swine flu virus. Human/Swine A/H1N1 Influenza Origins and Evolution

 

 

Health & Medical organisations

• The Royal College of General Practitioners: Information for GPs looking to prepare for enquiries about H1N1 and a preparation checklist
• British Medical Association: pandemic flu guidance for GPs

 

Blogs, wikis, alerts and other tools

• BBC: Fergus on flu
• WHO: interactive swine flu map
• Nature blog: swine flu
• Flu Wiki
• Wikipedia 2009 flu pandemic
• Flu tracker Map
• HealthMap. Global Disease Alert Map
• Microsoft Bing. 2009 Swine Flu H1N1
• Outbreak and Migration Map
• Facebook group. AH1N1 Swine Flu 2009
• Twitter aggregator. Outbreak.tweetmeme  

 

Last updated: 10.00 BST

The government today launched the National Pandemic Flu Service, a new online service that will assess patients for swine flu and, if required, provide an authorisation number that can be used to collect antiviral medication.

The system, which can also be accessed by telephone, is designed to take the strain off GPs as swine flu spreads. For the moment, it is only being used in England.

“The National Pandemic Flu Service is a new self-care service which will give people with pandemic swine flu symptoms fast access to information and antivirals”, said a department of health spokesman.

“This new service will free up GPs, enabling them to deal with other illnesses that need their urgent attention”.

The launch of the new system means important changes to the official advice given to those who think they may have swine flu.

That advice – and the new system itself – is supported by the Royal College of General Practitioners.

 

Latest advice

If you have flu-like symptoms and are concerned that you may have swine flu:

• Stay at home and check your symptoms at the National Pandemic Flu Service
• You should call your GP directly if:
  – you have a serious underlying illness
  – you are pregnant
  – you have a sick child under one year old
  – your condition suddenly gets much worse
  – your condition is still getting worse after seven days (five for a child)

Note: The National Pandemic Flu Service is a new online service that will assess your symptoms and, if required, provide an authorisation number that can be used to collect antiviral medication from a local collection point. For those who do not have internet access, the same service can be accessed by telephone on:

Telephone: 0800 1 513 100
Minicom: 0800 1 513 200

For more information on the National Pandemic Flu Service go to Flu Service – Questions and Answers

People in Scotland, Wales and Northern Ireland should visit www.direct.gov.uk/pandemicflu

 

Latest figures

There were an estimated 100,000 new cases of swine flu in the UK in the week ending July 19. Total deaths stand at 31. More than 800 people with swine flu have died worldwide since the beginning of the pandemic.

At this week’s update on the swine flu situation, Sir Liam Donaldson, Chief Medical Officer, also said:

• There are 840 seriously ill people in hospital with swine flu. Of these, 63 are in intensive care
• Under 14-year-olds continue to be the age group predominantly affected
• The provisional number of deaths in England related to swine flu is 26, and around 16% did not have any underlying health conditions. The figure is the same as last week because some unrelated deaths have been removed and others added. (This figure represents the number of deaths in individuals with swine flu but does not represent the number of deaths that can be attributed to swine flu).
• The disease is generally mild in most people so far, but is proving severe in a small minority of cases. 

Planning assumptions

Last week, the government released a Planning Assumptions paper outlining possible scenarios for how the pandemic might develop in the UK. It says that if the current growth in cases is sustained, a substantial wave of cases with up to 30% of the population experiencing symptoms could peak in early September, although a smaller but earlier peak is also possible.

Alternatively, seasonal effects might substantially slow the epidemic in July and August – perhaps to the extent of leading to a decline in weekly cases in August, before resurgence in the autumn, for example when schools reopen. If so, the overall peak of the pandemic might be delayed to October or even later.

These forecasts and others in the report are based on a "reasonable worst case" value and should therefore not be taken as a prediction of how the pandemic will develop. Planning against the reasonable worst-case scenario will ensure, however, that plans are robust against all likely scenarios.

Mortality planning assumptions range from 3,100 deaths in the UK to 65,000 deaths in a reasonable worst case scenario.

 

Advice for pregnant women

Many newspapers reported last weekend that pregnant women are being given confusing advice on swine flu.

Pregnant women are one of the higher risk groups for swine flu, as they are for all influenza viruses. It is therefore important for them to take precautions.

This website provides full and up-to-date advice for pregnant women and parents of young children. The advice has not changed recently and  is available at the following links:

Swine flu advice for pregnant women
Swine flu pregnancy and parenting Q&A
Swine flu symptoms, including high-risk groups
Chief Medical Officer’s advice on pregnancy, holidays, and parents

 

How dangerous is swine flu?

The vast majority of cases reported so far in this country have been mild. Only a small number have led to serious illness, and these have frequently been where patients have had underlying health problems. 

There has been an argument put forward that the government should restrict antivirals to those groups who are most at risk of developing serious complications from swine flu. In other words, if people are otherwise healthy, then the NHS should let the virus run its course, treating it with paracetamol and bed rest as you would normal flu.

Clinical trials of newly developed vaccines for swine flu have begun in the USA and Australia. These human studies will gather data on the safety and effectiveness of the vaccine.

 

Key points

The National Institute of Allergy and Infectious Diseases (NIAID), which is part of the National Institutes of Health in the USA, announced yesterday that a network of medical research institutions is about to begin a series of clinical trials to gather safety and efficacy data about some of the new influenza vaccines.

• At the same time, two vaccine manufacturers in Australia (CSL and Vaxine) have also begun testing their vaccine in healthy adult volunteers.
• The clinical trials will provide important early safety and efficacy data about the vaccines. In particular, the researchers will be monitoring adverse effects and immunogenicity (how well the vaccine provokes an immune response). They will also be assessing the dose required to be effective and whether the vaccine can be given alongside seasonal influenza vaccination.
• The American trials will be in healthy adult volunteers and in elderly volunteers who are also receiving the seasonal vaccine. If early results are positive, further studies may begin in healthy adolescents and children.
• The trials may take some months to complete, and the vaccination programmes are likely to begin before the full results are available. However, there should be sufficient results by September or October to spot real safety concerns and to allow governments to begin planning for the use and distribution of the new vaccines. Safety will continue to be monitored through surveillance when vaccination programmes are introduced nationally.

 

What are the WHO’s current recommendations for vaccines?

At a special meeting of the Strategic Advisory Group of Experts (SAGE) on July 07 2009, the WHO considered the potential options for vaccine use. They came up with some recommendations that were endorsed by the WHO Director-General, including:

• Healthcare workers should be immunised first.
• For other groups it is suggested that countries should decide their own vaccination policies and priority orders depending on country-specific conditions, possibly commencing with pregnant women and anyone aged over six months with one of several chronic medical conditions, followed by healthy young adults between 15 and 49 years of age, healthy children, healthy adults aged 50 to 64 years and healthy adults aged 65 years and above.
• Post-marketing surveillance of the vaccine is very important, particularly in certain population groups. This is because some new technologies are involved in the production of these vaccines and these have not yet been fully tested in certain groups. It is also important that results of this surveillance are shared widely in the international community so that countries can make any necessary adjustments to their vaccination policies.
• The production of particular types of vaccine formulations was also promoted, including live attenuated viruses and those that have oil-in-water adjuvants, which would help to protect against drifted strains of the virus (slightly mutated versions of the virus).

 

How are vaccines made?

To make a vaccine, a large amount of the virus or bacteria is needed. In the case of swine flu, the US Centers for Disease Control and Prevention (CDC) began isolating and preparing strains of the swine flu virus as soon as the first human case became known. These strains were sent to its counterparts in other countries including the National Institute for Biological Standards and Control (NIBSC) in the UK. These organisations prepare the virus strains to be used in making the vaccine.

Viruses can be grown in hens’ eggs, but often the infectious influenza virus strains do not grow well in eggs. To get around this, the infectious virus is injected into the eggs with another influenza virus that thrives in eggs. The two viruses swap pieces of their genetic material and produce hybrids, some of which both grow well in hens’ eggs and also have the elements of the disease-causing virus needed for a vaccine. These hybrids are isolated and the best candidate for making a vaccine is selected. This chosen hybrid strain is then grown and distributed to vaccine manufacturers.

The vaccine manufacturers use dead or weakened virus to create the vaccine. Other constituents can also be added to the vaccine, such as a suspending fluid to carry the virus into the body, preservatives and stabilisers that allow the vaccine to be stored safely, and chemicals to help the vaccine to promote an immune response.

 

When will a vaccine be available?

Vaccine development usually takes about six months and it began in April 2009. The WHO suggests that the first doses of influenza A H1N1 vaccine are expected as early as September 2009. The UK government says that the first batches of vaccine are expected to arrive in the autumn, and 30m double doses (enough for half the population) are expected to be available by the end of the year. The government has ordered enough vaccine for the whole population, and when it becomes available will focus on those at the greatest risk first.

 

Who will be a priority for vaccination?

The administration of the vaccines will need to be prioritised. The decision on prioritisation of the population will be taken on the basis of which groups are being most affected by the virus, when the vaccine arrives and how best to protect the NHS from being over-stretched.

 

How effective and safe will the vaccine be?

Vaccination is very effective in preventing and reducing the impact of serious illness. Although vaccines are not 100% effective and can become less effective if the virus mutates, they still offer some protection. Current flu vaccines last for about a year and give about 70-80% protection against infection with strains of influenza virus that are very similar to those used to make the vaccine. It is too early to predict how the swine flu virus might mutate. The WHO is closely monitoring it for changes, and this will help countries to make a quick response if the virus undergoes important changes.

The human trials that are currently underway will provide some evidence of the short-term safety and effectiveness of the vaccines. In particular, the researchers will be monitoring side effects and also how effectively the vaccine prompts a response from the immune system (its immunogenicity). The vaccines will be approved for use by national authorities. In this country the Medicines and Healthcare products Regulatory Agency (MHRA) is responsible for monitoring the safety of flu medicines and vaccines. Safety monitoring will be ongoing once the vaccine programme is introduced.

Links To The Headlines

NIH news: NIAID Set to Launch Clinical Trials to Test 2009 H1N1 Influenza Vaccine Candidates

CIDRAP: H1N1, seasonal flu vaccines to be tested together

”A pint of milk a day cuts chances of heart disease and stroke by up to a fifth,” The Daily Telegraph has said. The nation’s favourite dairy drink is also said to cut risk of developing diabetes and colon cancer. The findings may challenge the view held by some that too much dairy is bad for you.

These findings come from a systematic review that has combined the results of several observational studies,   which found that consuming higher amounts of milk or dairy products is associated with reduced risk of heart disease, stroke and diabetes.

However, there are some limitations of the study that have to be considered when drawing conclusions from these results, in particular that the studies reviewed used variable methods for assessing milk consumption and it is possible participants misreported the milk they drank. Several other factors not measured in this study could be playing a role in disease risk, such as other dietary patterns, physical activity and lifestyle habits. Furthermore, variable and inconclusive results were also obtained for fat content of milk, meaning the study could not compare whole milk with low-fat milk.

 

Where did the story come from?

Peter Elwood and colleagues of Cardiff University, the University of Reading and the University of Bristol carried out this research. No sources of funding were reported. The study was published in the peer-reviewed Journal of the American College of Nutrition.

What kind of scientific study was this?

This is a systematic review and meta-analysis in which the researchers used cohort and case-control studies to investigate whether milk and dairy consumption affected the outcomes of vascular disease and diabetes.

The authors searched the Medline medical database for relevant studies using the phrases milk, milk protein, dairy, dairy calcium, heart disease, coronary artery disease, myocardial infarction, ischaemic heart disease, stroke, diabetes or metabolic syndrome.

The authors included studies that collected data on milk consumption at the start of the study and then followed people up over a period, examining a range of medical outcomes.

Among the 324 studies identified by the search there were 11 suitable studies on milk products and heart disease, seven on milk and stroke and four on milk and diabetes/metabolic syndrome. The researchers pooled the results of these relevant studies to determine the risk of their respective outcomes in relation to levels of milk consumption.

Within these individual studies there had been attempts to make statistical adjustments to account for the influence of confounders, though the exact methods of adjustment varied between studies. The authors then obtained extra data from studies that gave disease risks in relation to the type of milk consumed, e.g. whole or low-fat.

Finally, the authors summarised conclusions from the recent report by the World Cancer Research Fund and American Institute for Cancer Research, looking at observations between cancer development and milk consumption.

 

What were the results of the study?

The authors pooled the results of 15 cohort studies examining risk of heart disease and stroke, featuring over 600,000 participants and extensive follow-up times, in the range of 8 to 25 years. They found that the risk of heart disease in subjects with the highest milk or dairy consumption was reduced by 16% compared to those with the lowest consumption (RR 0.84, 95% CI 0.76 to 0.93). When looking solely at the seven studies examining stroke events, the researchers found that stroke risk was reduced by about 21% (RR 0.79, 95% CI 0.75 to 0.82).

The combined results of the four studies examining the development of diabetes depending on milk consumption found that the risk was reduced by 8% among those with the highest milk intake (RR 0.92, 95% CI 0.86 to 0.97).

The studies examined featured adjustments for various confounders including age, sex, BMI, smoking, physical activity, social class, cholesterol and blood pressure.

When the authors looked across all of the studies for any that had given separate results for whole and low-fat milk, risk results were highly variable and were generally not significant.

The researchers also report on other studies carried out that had made similar observations to their own results. Four case-control studies observed that high milk consumption reduced the risk of metabolic syndrome, which is a combination of risk factors occurring together of elevated blood glucose, high cholesterol, being overweight or obese, and high blood pressure (RR 0.74, 95% CI 0.64 to 0.84).

Additionally, four case-control studies asking women who had had a heart attack about their prior consumption of milk, found 17% reduction in risk from drinking the highest quantity of milk (RR 0.83, 95% CI 0.66 to 0.99).

The Report of the World Cancer Research Fund was examined to look at data on the relationships between various cancers and dairy consumption. The report’s results were based on a variety of cohorts and case control studies. Variable associations were found for studies examining prostate, colon and bladder cancer, and no associations were found for other cancers.

 

What interpretations did the researchers draw from these results?

The authors conclude that the results of their review provide evidence of an overall survival advantage from consuming milk and dairy products, highlighting the high proportion of UK deaths currently attributable to vascular disease, cancer and diabetes.

 

What does the NHS Knowledge Service make of this study?

This review, which has combined the results of various observational studies, found that consuming higher amounts of milk or dairy products is associated with reduced risk of heart disease, stroke and diabetes.

However, the systematic review pooled the results of studies of varying quality, study length, inclusion criteria, disease outcomes and methods of assessing milk or dairy consumption. These individual studies may have had several biases. There are also other aspects of this study that must be considered when interpreting the results of the study:

• The researchers looked at case-control studies in which a person has already experienced the disease outcome, e.g. heart attack or stroke, and is then asked to recall their past consumption of milk. This may involve recall bias, where a person who has the disease recalls differently compared to those who have not, as a way to try to find a possible explanation.
• Additionally, the review pooled data from cohort studies, which have a design that may be more reliable for assessing causation as the person hasn’t yet developed the disease. However, these individual studies had considerable variability in their methods.
• One important variation was that milk consumption had been variably assessed through food questionnaires or 24-hour food recall, and such estimates are likely to involve some inaccuracy. Also, the studies used variable exposure categories. For example, some studies compared people who drank milk to people who did not. Others looked at number of days of the week milk was drunk on, others at the number of pints or glasses drunk per day or per week. As such, it is very difficult to gain any indication of the optimal quantity of milk to consume. Furthermore, it is unclear whether other dairy sources such as cheese, yoghurt or cream had been assessed.
• There were differences in results between some of the cohort studies. As the authors say when pooling the studies evaluating risk of heart disease they excluded the results of one study, in which reduced risk was observed from consumption of low-fat milk, but increased risk with consumption of whole milk. This finding differed from the other studies pooled.
• The individual studies had attempted to adjust for different confounders but there was inconsistency between studies in the factors that had been considered. Particularly, important lifestyle ones such as other dietary habits or physical activity, smoking or alcohol consumption may be confounding results.
• Randomised controlled trials would be the best way to investigate the health benefits of drinking milk but the researchers think these are unlikely to be practical to perform.
• There were no consistent results associating milk with risk of any type of cancer. Also, variable and inconclusive results were obtained in assessment of whole compared to low-fat milk.
• Conclusions that drinking more milk reduces risk of death are only indirect ones, following on from the fact that heart disease, stroke and diabetes are a significant cause of morbidity and mortality in the UK. The studies in this review have not actually examined death rate, survival or quality of life in those who did or did not develop disease.

Links To The Headlines

A pint of milk a day cuts chances of heart disease and stroke. The Daily Telegraph, July 23 2009

Drinking milk cuts ‘risk of dying from heart disease and stroke by one fifth’. Daily Mail, July 23 2009

Links To Science

Elwood PC, Givens DI, Beswick AD et al. The Survival Advantage of Milk and Dairy Consumption: an Overview of Evidence from Cohort Studies of Vascular Diseases, Diabetes and Cancer. JACN, 2008

A review of research on how flu affects immunosuppressed people and the effects of vaccination on them has been published in The Lancet Infectious Diseases. The authors specifically looked at susceptibility in people with HIV/AIDS, cancer, those who have had a solid organ transplant or bone-marrow transplant and patients on haemodialysis or steroids.

Such groups are thought to be at higher risk of serious influenza-associated complications and as such are priority groups for immunisation.

However, treatments for immune dysfunction may also limit the effectiveness of vaccination and there may be complications from the vaccination itself in these groups. The evidence behind these issues is discussed in this review.

 

Key points from the review

• There is little research on using vaccination to prevent influenza in immunosuppressed people. This review found just one randomised clinical trial. This trial of HIV-infected patients found high vaccine effectiveness.
• The same immune dysfunction that can increase the risk and consequences of influenza infection might also compromise vaccine responses and effectiveness.
• Most immunosuppressed populations are at higher risk of influenza-associated complications, have a general trend toward impaired antibody responses but can be safely vaccinated.
• The priority for control of influenza is focused on generating effective antibody responses with vaccines. Progress is being made at increasing the scale, duration, and breadth of vaccine responses to the two main surface proteins H and N (haemagglutinin and neuraminidase) in both healthy and immuno-compromised populations.
• There are two main types of influenza vaccine and both are being developed for the new H1N1 swine flu virus. One involves inactivated vaccines that contain viruses grown in eggs (mostly) and then killed. The other involves live weakened H1N1 vaccines.  The researchers say that previous concerns that these live attenuated vaccine would pose a risk to people that are immunocompromised have not been demonstrated by the studies in their review. Research into this area and into and other novel approaches to flu vaccine development are important. They ask that efficacy studies of attenuated vaccines in adults that are immunocompromised are also considered.

 

Where was the article published?

The research was carried out by Dr Ken M Kunisaki from the Minneapolis VA Medical Center and Edward N Janoff from the University of Colorado Denver School of Medicine.

The study was published in The Lancet Infectious Diseases. It was supported by grants from the National Institutes of Health and the Veterans Affairs Research Service.

 

What kind of study was this?

In this review, the researchers looked at the susceptibility of immunosuppressed people to the H1N1 swine flu virus, and the possible effectiveness and side effects of upcoming vaccines. Specifically, the authors looked at susceptibility in people with HIV/AIDS, cancer, those who have had a solid organ transplant, or bone-marrow transplant and patients on haemodialysis.

They say: “Although influenza vaccination is widely recommended for people that are immunosuppressed, the same immune dysfunction that can increase the risk and consequences of influenza infection might also compromise vaccine responses and effectiveness.”

The researchers aimed to investigate:

• the incidence and mortality rates of influenza infection among adults who are immuno-compromised,
• the risks and adverse effects of vaccination,
• the ability of a vaccine to get appropriate immune responses, and
• the clinical effectiveness of vaccination in these populations.

The researchers searched Medline through the years 1966-2009 for articles on adult influenza, its  frequency, complications, and antibody or clinical responses to vaccination. The antibody responses were measured as the percentage of people with levels of antibody protective against H3N2, and the clinical responses were defined as the frequency of influenza reported during the total observation period. They also looked for policy recommendations and guidelines. Excess deaths and hospitalisations were also reported. They only included articles reporting outcomes related to inactivated vaccines, because live attenuated vaccines are not recommended in immuno-compromised groups because there is a theoretical possibility of causing the disease itself.

 

What was found?

The researchers discussed the following:

HIV/AIDS

Studies show that the numbers of HIV/AIDS patients admitted to hospital with flu has fallen substantially since the introduction of effective antiretroviral therapy. However, admissions are still higher than in the general population.

HIV/AIDS patients generally have lower antibody responses to vaccination, but several studies have shown that vaccination leads to fewer and less severe cases of flu in these patients. Larger randomised trials are needed to assess vaccination, particularly among those with more advanced disease as measured by low CD4+ cell counts.

Transplantation

People who have had solid organ transplants (such as lungs, kidneys or livers) also have higher flu infection rates due to the immunosuppressant drugs they take to prevent organ rejection. Lung transplant recipients are particularly prone to infection and kidney transplant recipients can suffer rejection if they contract flu. In theory, vaccination in these populations could also stimulate a T-cell response, leading to rejection, but the researchers say that most studies say this does not occur.

The intensive pre-transplantation regimens used in preparing people for bone marrow (haematopoetic stem cell) transplants leave patients deeply immunocompromised for up to several months after transplantation.  A study on 10 patients’ response to vaccination showed that there was a complete lack of serological response within six months in all 10.

Malignancies and chemotherapy

Chemotherapy can produce major immunosuppression in people with cancer and one study shows that 21-33% of cancer patients contracted flu and were admitted to hospital with respiratory symptoms during one recent seasonal flu epidemic.

Timing of flu vaccination can be crucial in cancer patients. The response might be best between chemotherapy cycles, or more than seven days before chemotherapy starts.

Haemodialysis

Infections are the second leading cause of death in patients on dialysis, and lung infections such as flu are particularly serious. Vaccinated patients on dialysis have been shown to have a lower chance of hospital admission or death from any cause than unvaccinated patients.

Systemic corticosteroids

The authors also looked at people taking oral or inhaled steroids, saying that the evidence shows flu vaccination is both safe and often stimulates an immune response. However, the vaccine’s clinical effectiveness in reducing episodes of flu in people taking the drugs has not been well tested.

 

What were the researchers’ conclusions?

The researchers say that most immunosuppressed populations are at higher risk of influenza-associated complications. These people have impaired antibody responses to the vaccine (although data for this conclusion is mixed. For example, in some trials, HIV patients with low CD4+ counts developed only 30% of the antibody response of healthy controls, and in one trial of patients on chemotherapy, there was even less of a response. However, other studies have shown that patients who have had haemodialysis and transplant managed up to 80% protective titres.

They say that most immunosuppressed people can be safely vaccinated (although longitudinal data that follows up patients over time are largely lacking).

They also say that the small number of studies of cellular responses to influenza vaccination, in relatively small numbers of immunosuppressed individuals, showed impaired cellular responses among a few patients.

The researchers call for better trial data to inform vaccination recommendations based on the effectiveness and cost in these at-risk populations.

 

What does the NHS Knowledge Service make of this study?

This study has addressed an important question in vaccination research and one that has become topical with the spread of the new H1N1 swine flu virus. It is disappointing that there are so few high quality trials in this area and that the trials that exist are observational studies. This means that the evidence presented may be prone to bias. Nevertheless, decisions on vaccination in high-risk groups need to be made on the balance of the evidence that exists. This review has presented a useful summary, which can guide practice.

Links To Science

Kunisaki KM, Janoff EN. Influenza in immunosuppressed populations: a review of infection frequency, morbidity, mortality, and vaccine responses. Lancet Infect Dis 2009; 9: 493–504 

 

“A simple saliva test could help to cut the toll of potentially dangerous premature births,” the Daily Mail has reported. It says that new research has created a test that detects levels of the hormone progesterone, which can be used to identify those pregnant women most likely to give birth prematurely. According to the newspaper, high levels of progesterone help to stop the womb contracting before the full term of 40 weeks, whereas low levels put women at risk of delivering more than six weeks early.

In the study, the researchers analysed saliva samples from 92 pregnant women who were considered to be at risk of an early birth because of a previous premature delivery. The researchers then compared the levels of the hormone seen each week from 24 to 34 weeks of pregnancy with levels found in women who had babies born after 37 weeks.Twelve women who gave birth before 34 weeks were found to have lower levels of progesterone than those who had their babies at 37 weeks or later.

The small study had a few limitations but demonstrated the concept that a simple hormone test can have some predictive value. The research will also add to an understanding of the problem of early birth, hopefully leading to improved care for the 7% of babies born prematurely each year.

 

Where did the story come from?

This study was carried out by Dr Lachelin and colleagues from University College London and Kings College London. The study was funded by Tommy’s the Baby Charity and supported by an award from the National Institute for Health Research. It was published in the peer-reviewed, British Journal of Obstetrics and Gynaecology.

 

What kind of scientific study was this?

This was a cohort study in which the researchers measured the levels of the hormones oestriol (E3) and progesterone in the saliva of pregnant women known to be at risk of premature delivery.

The researchers explain that the rates of premature birth in developed countries have remained unchanged over several decades, affecting about 7% of deliveries. They also knew from previous work and animal studies that labour is preceded by biological changes, namely a decrease in progesterone and an increase in concentrations of the oestrogen-like hormone oestradiol (E2).

While studies have found no increase in the ratio of E2 to progesterone before the onset of term labour, there is an increase in the ratio of E3 to progesterone in the saliva prior to full-term labour and in women who deliver preterm.

In this study, the researchers took weekly saliva samples from women at increased risk of
preterm delivery from 24-weeks gestation onwards. The women were mainly recruited from 12 centres, (with a few self-referrals), as part of another study, the PREMET study. In the PREMET study, the researchers assessed the potential benefit of a drug in preventing premature birth in 892 women. Only the 111 women who provided saliva samples in this study were eligible for this subsequent research, and only 92 of these women consented or had sufficient samples taken for a complete analysis to be performed.

The researchers measured progesterone concentration, E3 concentration and E3 to progesterone ratio. They then made statistical adjustments to account for expected weekly changes in hormone levels and to allow for repeated measurements.

In the main analysis, they compared 64 women who delivered at term with the 12 women who delivered before 34 weeks and the 52 who delivered between 34 and 37 weeks.

The researchers also say that because of promising data from clinical trials, progestogen supplementation is now being widely investigated as a preventative intervention in women at risk of preterm labour.

 

What were the results of the study?

Salivary progesterone was significantly lower in the 12 women who delivered before 34 weeks than in those who delivered both at between 34 and 37 weeks or at term. The E3:progesterone ratio was also higher in the women who delivered before 34 weeks: this was in line with the progesterone results, but was not a statistically significant result.

 

What interpretations did the researchers draw from these results?

The researchers say that the measurement of saliva progesterone “may be of value in the prediction of early preterm labour” and in “determining which women might benefit from progesterone supplementation”.

 

What does the NHS Knowledge Service make of this study?

The lower progesterone concentration seen in the women who delivered before 34 weeks lends support to the theory that an imbalance between these hormones may be associated with preterm labour in some women.

As an exploratory study, this research does have some limitations in its methods, which should be considered when interpreting its results:

• This was a small, non-randomised study and therefore the 12 women who delivered before 34 weeks may have differed from those who delivered later in ways the researchers were unaware of. For example, most of those who delivered early already had lower levels of progesterone at 24 weeks. This could suggest that the women may have a predisposition to both lower progesterone and premature labour because of some other unknown factor.
• The selection methods used in the trial that originally supplied these women means they will not necessarily be representative of all women at risk of preterm labour. This means that further research will be needed to assess how applicable this test might be for general use among all pregnant women.
  ? A statistical test of how well the saliva samples discriminate between those women who will deliver early or not (its predictive power) was low. This suggests the test will need to be used alongside other clinical tools to improve its predictive power.
• As the study did not test progesterone supplementation, it is not possible to say from this research if this will be useful in preventing preterm births.

Overall, this study has shown that this simple test has some potential for use alongside other clinical tests and may, following further study, prove useful in identifying women at risk of preterm labour.

Links To The Headlines

Saliva test for early birth risk. BBC News, July 22 2009

Saliva test that spots hormone levels in pregnant women ‘could cut premature births’. Daily Mail, July 22 2009

Links To Science

Lachelin GCL, McGarrigle HHG, Seed PT et al. Low saliva progesterone concentrations are associated with spontaneous early preterm labour (before 34 weeks of gestation) in women at increased risk of preterm delivery. BJOG, [Early view publication] July 22 2009.

The virus responsible for the Spanish flu in 1918 created a ‘viral legacy’ that continues to this day, according to a study published recently in the New England Journal of Medicine.

According to the authors of the report, the Spanish flu’s H1N1 virus, which caused tens of millions of deaths in 1918, was also transmitted from humans to pigs during the pandemic. Tracing the lineage of the virus in this research shows that it continues to evolve in both humans and pigs 90 years later.

All human-adapted influenza A viruses "are descendants, direct or indirect, of that founding virus" says Jeffrey Taubenberger, a co-author of the report and a senior investigator at the Laboratory of Infectious Diseases of the National Institute of Allergy and Infectious Diseases in the US.

 

Key points from this research

• All flu viruses contain eight genes in total, including two that contain instructions for producing the proteins hemagglutinin (H) and neuraminidase (N), which allow the virus to attach to a host cell and spread from cell-to-cell.
• There are 16 sub-types of the H protein and nine sub-types of the N protein a flu virus can possess. This offers 144 possible HN combinations, but to date, only three (H1N1, H2N2 and H3N2) have been observed to be fully adapted for infecting humans.
• There are other combinations, such as H5N1, a strain of bird flu virus, but these have only occasionally infected a small number of humans.

 

Where was the article published?

This article was written by D M Morens and colleagues from the National Institute of Allergy and Infectious Diseases, Bethesda, in the US. It was published in the New England Journal of Medicine. No potential conflicts of interest were reported.

A related article on the evolution of the current pandemic strain of the H1N1 virus was also published in the same issue and has been covered in Behind the Headlines.

 

What kind of study was this?

This was a review article written by acknowledged experts in the field, explaining the lineage of the pandemic flu virus seen in 1918 and relating it to the emergence of the pandemic H1N1 strain currently circulating.

 

What do the researchers say?

The researchers explain that descendents of the H1N1 influenza A virus that caused the pandemic of 1918–1919 have persisted in humans for over 90 years, and have continued to contribute their genes to new viruses that have caused epidemics, new pandemics and epizootics (epidemics in animal populations).

The current pandemic strain is thought to originate from two unrelated swine viruses, including a derivative of the 1918 human virus. It also appears to contain genes from human, bird and swine flu viruses. The authors sought to detail the family history or ‘lineage’ of this virus, mapping out the complex relationship between a number of different strains that may have exchanged genetic material.

The authors created an analogy to explain how genetic material transfers and mutates. They said it is helpful to think of influenza viruses as a team of eight genes working together. Occasionally the viruses ‘trade’ one or more team members to make way for new genes, or ‘players’. These new players bring with them ‘unique skills’, and through trading genes in this way (called ‘shift’) and by accumulating mutations (called ‘drift’) the influenza viruses are able to change and evade the immune system.

The authors also researched the mortality rates in seasonal epidemics and previous pandemics, expressing doubt over the claim that gene shift always cause severe pandemics while drift leads to more modest increases in seasonal mortality.

The authors raised several more interesting points in their article:

• Influenza pandemics over several centuries have shown a big variation in severity, ranging from mild to severe.
• The new swine flu virus is a fourth-generation descendant of the 1918 virus.
• It appears that successive pandemics and pandemic-like events generally appear to be decreasing in severity over time. They say this is probably due to medical and public health advances.

 

What is the implication and importance of this?

This report helps to explain the evolution of the current pandemic strain of influenza virus, an area where extensive study can be expected. Although the genetic code of this virus has already been sequenced, this type of research may help in the search for effective vaccines, which remain the best hope for minimising the complications expected.
 
The authors say that while “we must be prepared to deal with the possibility of a new and clinically severe influenza pandemic caused by an entirely new virus, we must also understand [the current pandemic] in greater depth” and continue to “explore the determinants and dynamics of the pandemic era in which we live."

Links To The Headlines

Spanish flu created a viral dynasty: study. AFP, June 30 2009

Links To Science

D. M. Morens, J. K. Taubenberger, and A. S. Fauci. The Persistent Legacy of the 1918 Influenza Virus, NEJM; 361:225-229. July 16, 2009

Garten RJ, Davis CT, Russell CA, et al. Antigenic and genetic characteristics of swine-origin 2009 A(H1N1) influenza viruses circulating in humans. Science, July 10 2009 325: 197-201; published online May 22 2009

“Stressed-out mums and dads could be to blame for the epidemic in childhood asthma,” the Daily Mirror reported. It said a study of almost 2,500 healthy children over three years found that those exposed to more air pollution were more likely to develop asthma, and that parental stress increased this risk even more.

This study suggests that socioeconomic status and parental stress may increase the risks associated with traffic-related pollution and maternal smoking on pregnancy although by themselves they do not appear to affect asthma risk.

The study does have some limitations, including the fact that socioeconomic status was based only on the level of parental education, parental stress was only measured at one time point and that many of the factors assessed including children’s diagnoses, were based on reports from the parents only and   not independently verified. Further studies will need to confirm these results.

 

Where did the story come from?

The research was carried out by Dr Ketan Shankardass and colleagues from the Li Ka Shing Knowledge Institute of St Michael’s Hospital, Canada and two US universities. It was funded by the National Institute of Environmental Health Sciences, the US Environmental Protection, a National Cancer Institute Grant, the Hastings Foundation, and the Canadian Institutes of Health Research.

The study was published in the peer-reviewed scientific journal, Proceedings of the National Academy of Sciences of the United States of America.

 

What kind of scientific study was this?

This research is part of a prospective cohort study called the Southern Californian Children’s Health Study. The study has already shown that traffic-related pollution and maternal smoking during pregnancy were associated with an increased risk of asthma in children. The current analyses aimed to look at whether socioeconomic status and parental stress might increase the risk of asthma even further in children exposed to pollution and maternal smoking.

The researchers enrolled children between five and nine years of age, who were attending schools in 13 communities in southern California in 2002 and 2003. All students from the study communities were asked to participate and 65% (5,349 children) returned the study questionnaires given. These questionnaires asked about the children’s health, including questions about chest-related conditions and allergies. They also asked about other factors such as race, gender, where they lived, type of medical insurance coverage, whether they had been exposed to maternal smoking during pregnancy or if anyone in the home currently smoked on a daily basis, and family history of asthma. Each household’s exposure to traffic-related pollution was estimate, based on their location and distance from local ‘measured’ sources of pollutants, such as traffic.

Parental education was used as a measure of the family’s socioeconomic status. Parental stress levels were measured at the start of the study using a standard question (the Parental Stress Scale, PSS):

“In the last month, how often have you felt:

• (a) that you were unable to control the important things in your life;
• (b) confident about your ability to handle your personal problems;
• (c) that things were going your way; and
• (d) your difficulties were piling up so high that you could not overcome them.”

The parents rated how often they felt each of these on a scale of zero to four, and the scores were summed to give a score from zero to 16 (higher scores indicating greater stress).

The children’s living conditions were assessed using questions about: type of home; whether the child lived elsewhere for more than 50 days a year; previous water damage or flooding in the home; the presence of mould or mildew on household surfaces, the presence of a musty smell and cockroaches or pets in the home. There were also questions about whether gas stoves, air conditioners, humidifiers or vaporisers were used in the home and whether the child’s bedroom had a carpet.

The researchers excluded children who had already been diagnosed with asthma those who had wheezing episodes, and those who did answer or know. Children whose exposure to traffic-related pollution could not be assessed, and those who were lost to the follow up carried out in the first year of the study were also excluded. This left 2,497 children for analysis. Just over half of the children (55%) were Hispanic, just over a third non-Hispanic white (36%), 3% African American, and 6% of other races or ethnic groups.

During the three years of follow up, the children’s parents filled out annual questionnaires about the children’s health, including whether they had been diagnosed with asthma. The researchers looked at how the factors assessed affected a child’s risk of developing asthma during the follow up. In particular, they looked at the effects of traffic-related pollution and maternal smoking during pregnancy, and whether parental stress or socioeconomic stress affected the level of risk associated with these factors. They took into account the factors that they measured that could affect outcome in their analyses, such as age, gender, and ethnicity.

 

What were the results of the study?

About 21% of families were defined as being of low socioeconomic status because the parents had not finished high school. On average, parental stress score was 3.85 on the PSS (the most stressed score possible was 16).

Just under 5% of children (120 children) developed asthma during the follow up. African American children were more likely than Hispanic children to develop asthma. Children who were underweight, had a history of chest illness or allergy, who lived in a home with a musty smell or whose parents had asthma were also more likely to develop asthma.

Low socioeconomic status and higher parental stress alone did not increase the risk of developing asthma.

Increasing exposure to traffic-related pollution did increase the risk of childhood asthma. Among children in low socioeconomic status families or those with parents with higher levels of stress, the effects of traffic-related pollution were greater than in children from high socioeconomic status families or parents with lower levels of stress. The effects of socioeconomic status were reduced if parental stress was taken into account.

Exposure to maternal smoking during pregnancy did not significantly increase the risk of childhood asthma overall. However, exposure to maternal smoking during pregnancy did significantly increase risk of childhood asthma in children from low socioeconomic status families or those with parents with higher levels of stress.

 

What interpretations did the researchers draw from these results?

The researchers conclude that, “children whose parents perceived their lives as unpredictable, uncontrollable, or overwhelming had increased risk of new onset asthma associated with [traffic-related pollution] and maternal smoking during pregnancy”. They also say, “understanding the role of air pollution in the causation of complex diseases like asthma requires consideration of how social factors may modify the effects of environmental exposures”.

 

What does the NHS Knowledge Service make of this study?

This study suggests that socioeconomic status and parental stress may exacerbate the risks associated with traffic related pollution and maternal smoking on pregnancy, although by themselves they do not appear to affect asthma risk. It has the advantage of having collected the data over time (prospectively), however, there are some limitations to note:

• As with all studies of this type, the relationship between parental stress, socioeconomic status and asthma risk may be due to other factors that are not balanced between the groups. The researchers did try to take some of these factors into account in their analyses, but this may not have fully removed their effects and could not remove the effects of unknown or unmeasured factors. In particular, parental stress may be an indicator of other problems that could affect a child’s risk of asthma.
• Socioeconomic status was defined based only on the level of parental education. A more accurate measure may have been attained if the researchers had also looked at other factors such as family income and area of residence. In addition, a large proportion of Hispanics were of low socioeconomic status (35.0%) compared to those with non-Hispanic background (4.0%) and although ethnicity was taken into account in the analysis, it could still have affected the results.
• Only a small number of mothers (6.3%) were reported to smoke during pregnancy. The results for this group would be more reliable if a larger number of exposed children had been available for analysis.
• Many of the factors assessed were based on the parents’ reports, including children’s asthma diagnoses and maternal smoking during pregnancy. This may mean that some of the information may not have been accurate, due to missed diagnoses, inaccurate recall or misreported information.
• Parental stress was only measured at one time point (the month preceding the start of the study), and this may not have accurately reflected their usual stress levels or stress levels over a longer period.
• The results may not apply to children from age groups or ethnic groups different to those studied.

Further studies will be needed to confirm these results.

Links To The Headlines

Stressed parents up asthma risk. BBC News July 21 2009

Childhood asthma ’caused by stressed parents’. The Daily Telegraph, July 20 2009

Stress link to asthma. Daily Mirror, July 21 2009

Links To Science

Ketan Shankardass K, McConnell R, Jerrett M, et al. Parental stress increases the effect of traffic-related air pollution on childhood asthma incidence. PNAS 2009; Published online before print July 09