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Health News from NHS Choices

Constantly updated health news across a range of subjects.

NHS Choices News

  • Healthy diet could cut risk of Alzheimer's disease

    "A new diet could more than halve a person's risk of developing Alzheimer's disease," the Mail Online reports.

    In a new study, researchers looked at the effects of three diets on the risk of developing Alzheimer's disease. These were:

    • a standard Mediterranean-type diet
    • the Dietary Approach to Stop Hypertension diet (DASH) – designed to reduce blood pressure
    • Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) – this combines elements of the Mediterranean diet and the DASH diet

    The study found older people whose usual diet was close to any one of these three healthy diets were less likely to develop Alzheimer's disease than those eating less healthily.

    The researchers say they found the greatest effect from the MIND diet, which is rich in green leafy vegetables, wholegrains, nuts and berries, even if people didn't follow it closely. Participants who did stick rigorously to the MIND diet were 52% less likely to be diagnosed with Alzheimer's disease.

    This large observational study can't show that the diets protected against Alzheimer's, only that there seems to be a link between eating a healthy diet and a lower risk of getting Alzheimer's disease. The three diets weren't compared directly, so we can't be sure which one is best.

    The study provides further evidence that eating a healthy diet may reduce the chances of developing Alzheimer's disease

    Where did the story come from?

    The study was carried out by researchers from Rush University Medical Center in Chicago and Harvard School of Public Health in Boston, and was funded by grants from the US National Institute on Aging.

    It was published in the peer-reviewed medical journal Alzheimer's & Dementia.

    The Mail Online reported the study accurately for the most part, although it did not say that this type of study cannot prove causation. Strangely, it repeatedly said that the MIND diet called for a daily salad, although salad was not mentioned specifically in the study.  

    What kind of research was this?

    This was a large prospective cohort study of older people who were taking part in a long-running study of memory and ageing. It aimed to see whether people whose food consumption was closest to one of three types of healthy diet were less likely to be diagnosed with Alzheimer's disease during the course of the study.

    As this was an observational study, it cannot prove that the diet protected against Alzheimer's disease or other types of dementia. A randomised controlled trial would be needed for that.  

    What did the research involve?

    Researchers worked with volunteers living in retirement communities and public housing in Chicago. They were asked to complete a questionnaire to assess their diet. They all had annual neurological examinations for an average of four to five years, which checked for Alzheimer's disease.

    Researchers adjusted the results to take account of other factors that can affect Alzheimer's risk. They then looked for links between Alzheimer's diagnosis and people's diets.

    At the start of the study, the researchers decided to assess three types of diet:

    • The Dietary Approach to Stop Hypertension (DASH) has been used to reduce blood pressure and stroke risk. It includes total grains and wholegrains, fruit, vegetables, dairy products, meat and fish, nuts and legumes, but restricts fat, sweets and salt.
    • The Mediterranean diet (MEDdiet) is often recommended for heart health. It includes olive oil, wholegrains, vegetables, potatoes, fruit, fish, nuts and legumes, and moderate wine, but restricts full-fat dairy products and red meat.
    • The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet is a new diet developed by the researchers with elements from the DASH and MEDdiet, and also includes foods thought to protect the brain. It includes olive oil, wholegrains, green leafy vegetables, other vegetables, berries, fish, poultry, beans and nuts, and a daily glass of wine, but restricts red meat and meat products, fast or fried food, cheese, butter, pastries and sweets.

    Using questionnaires from 923 volunteers, the researchers assessed how well each of them scored on each diet. They divided people into three groups showing high, moderate or low scores for each diet.

    They then looked at whether people in the high-scoring groups for each diet were less likely to be diagnosed with Alzheimer's disease during the average 4.5 years of follow-up, compared with people in the low-scoring groups.

    People diagnosed with other types of dementia, such as dementia with Lewy bodies or vascular dementia, were not included as Alzheimer's cases.

    The researchers did a good job of checking for other factors that could affect Alzheimer's risk. This included testing for a type of gene (APOE) that raises the risk of Alzheimer's, as well as asking about people's education level, whether they took part in cognitively stimulating activities such as playing games and reading, how much physical activity they got, their body mass index (BMI), whether they had symptoms of depression, and their medical history.  

    What were the basic results?

    During the study, there were 144 cases of Alzheimer's disease among the 923 people taking part.

    People with the highest scores in all three diets were less likely to be diagnosed with Alzheimer's disease than people with the lowest scores.

    The link was slightly stronger for the MIND and MEDdiet than the DASH diet. People who had the highest scores on the MIND diet were 52% less likely to be diagnosed with Alzheimer's disease (hazard ratio [HR] 0.48, 95% confidence interval [CI] 0.29 to 0.79).

    People who had moderate scores for the MIND diet were also less likely to be diagnosed with Alzheimer's than those with the lowest scores, but the link was not as strong (HR 0.64, 95% CI 0.42 to 0.97). Moderate scores on the DASH and MEDdiet did not show a statistically significant reduction in risk.  

    How did the researchers interpret the results?

    The researchers said their results showed that "even modest adherence" to the MIND diet "may have substantial benefits" for preventing Alzheimer's disease.

    They say that while the DASH and MEDdiet also showed positive results, "only the highest concordance" with those diets was linked to the prevention of Alzheimer's disease.

    They go on to speculate that the dairy and low-salt recommendations in DASH, while useful for reducing blood pressure, may not be particularly relevant to brain health.

    They concluded that, "High-quality diets such as the Mediterranean and DASH diets can be modified ... to provide better protection against dementia." 

    Conclusion

    The study found people who ate a healthy diet – with plenty of green vegetables, wholegrains, legumes and less red meat – may be less likely to get Alzheimer's disease. However, we should be wary of saying that their diet actually protected them from Alzheimer's, as it is a complex disease with many potential causes.

    The main limitation is that observational studies cannot prove causation, even when researchers take care, as they did here, to include factors that we know affect disease risk. It's also notable that the researchers excluded dementia, other than Alzheimer's disease, from their calculations.

    It would be interesting to see the effect of these diets on other types of dementia, too, especially as the DASH diet protects against hypertension, which can be a cause of vascular dementia. This was not taken into consideration when the authors concluded that low dairy and salt may not be needed for brain health (though they still remain part of a healthy, balanced diet).

    Another limitation is that the food frequency questionnaire may not have completely captured people's adherence to the three diets. For example, people were asked about how often they ate strawberries, not about other types of berries. This could underestimate the effect of berry consumption in the diet.

    Experts already think a healthy lifestyle can help lower the risk of getting dementia. Recommendations include eating a healthy diet, keeping to a healthy weight, exercising regularly, not smoking, drinking in moderation, and keeping blood pressure healthy. The question is: what type of healthy diet is best?

    This study suggests the MIND diet may be better at lowering the risk of Alzheimer's disease than two other healthy diets. However, the study did not compare the effect of the diets directly.

    We also don't know which foods in the diets might make the difference. The best advice may be to follow a healthy balanced diet, without worrying too much about exactly which foods might protect your brain.

    Analysis by Bazian. Edited by NHS ChoicesFollow Behind the Headlines on TwitterJoin the Healthy Evidence forum.

    Links To The Headlines

    The 10 foods that HALVE the risk of Alzheimer's and the 5 that harm the brain: Stock up on berries, salad and wine - but avoid cheese, pastries and sweets. Mail Online, March 30 2015

    Links To Science

    Morris MC, Tangney CC, Wang Y, et al. MIND diet associated with reduced incidence of Alzheimer's disease. Alzheimer's & Dementia. Published online February 11 2015



  • Sperm quality pesticides claim 'should be treated with caution'

    "Pesticides on fruit and vegetables may be damaging sperm counts and men should consider going organic if they want to have children," The Daily Telegraph reports.

    A study found men who ate the highest amount of fruit and vegetables with high levels of pesticides had a 49% lower sperm count, as well as a 32% lower count of normally formed sperm, than men who consumed the least amount. Sperm can sometimes be an abnormal shape, making it harder for them to move and fertilise an egg.

    The results of this study should be viewed with caution. Researchers did not assess individual diets for pesticide residues. They also did not know if the food the men ate was grown organically or conventionally (a failing The Telegraph overlooked). 

    So it is possible the men's dietary exposure to pesticides was misclassified. The men in the study were all attending fertility clinics, so the results may not apply to the general population.

    The study certainly should not be seen as an invitation to avoid eating fruit and vegetables. Aside from the general health harms a fruit and veg-free diet would hold, this could also negatively impact your sperm quality.

    Many factors can affect men's sperm count and quality, including whether they smoke or drink alcohol, as well as how much exercise they take and their weight. Whether or not pesticide residue found in our diet is another factor that affects sperm quality is an important topic that needs further study. 

    Where did the story come from?

    The study was carried out by researchers from the Harvard T H Chan School of Public Health, Massachusetts General Hospital, Brigham and Women's Hospital, and Harvard Medical School in the US.

    It was funded by the National Institute for Environmental Health Sciences, the National Institutes of Health, and the Ruth L Kirschstein National Research Service Award.

    The study was published in the peer-reviewed journal Human Reproduction on an open-access basis, so it is free to read online.

    The study was covered uncritically by most of the UK media. The Telegraph's assertion that, "Men who eat fruit and vegetables with high pesticide residues could double their sperm count by switching to organic food" was highly misleading.

    The study did not compare the effects of organic and non-organic food on sperm count. However, both The Telegraph and the Mail Online included comments from UK experts. 

    What kind of research was this?

    This was a cohort study exploring whether the consumption of fruits and vegetables with high levels of pesticide residues is linked to lower semen quality.

    This type of study cannot prove cause and effect, as other factors could be causing any effects seen. However, in studies of this type, researchers try to take account of other factors that can affect a health outcome.

    In this case, for example, male fertility is known to be affected by lifestyle factors such as smoking and weight, which were taken into account in the statistical analyses.

    The researchers say in nearly one-third of couples seeking help with conception the problem is one of male infertility.

    They say occupational exposure to pesticides has been linked to lower sperm counts, and argue that pesticide exposure may explain a general decline in semen quality. Whether pesticide exposure through diet could affect male fertility is unknown. 

    What did the research involve?

    Men attending a fertility clinic filled out food frequency questionnaires from which the researchers estimated their intake of pesticides from fruit and vegetables. The results were then analysed to look for an association between higher pesticide consumption and lower sperm counts.

    Researchers used an ongoing study of couples attending a US fertility clinic. The men in the study had to be aged between 18 and 55 without any history of vasectomy, and be in a couple seeking fertility treatment with their own eggs and sperm.

    Between 2007 and 2012, the male partners in sub-fertile couples (couples who require medical assistance to conceive) completed a food frequency questionnaire. They were asked how often on average they consumed specified amounts of fruit and vegetables over the previous year using standard portion sizes.

    The fruit and vegetables were categorised as being high, moderate or low in pesticide residues based on data from the annual United States Department of Agriculture Pesticide Data Program.

    Fruit or vegetables low in pesticide residues included peas, beans, grapefruit and onions. Those with high residues included peppers, spinach, strawberries, apples and pears. This data takes account of how food has been prepared, such as whether it has to be peeled.

    By this criteria, 14 of the fruits and vegetables in the questionnaire were categorised as high in pesticide residues and 21 as low-to-moderate in pesticide residues.

    The researchers divided the men into four groups, ranging from those who ate the greatest amount of fruit and vegetables high in pesticide residues (1.5 servings or more per day), to those who ate the least amount (less than half a serving per day).

    They also categorised whether men ate a "prudent" diet – consisting of high intakes of fish, chicken, fruit, vegetables and wholegrains – or a "Western pattern" – high intakes of red and processed meat, butter, high-fat dairy, refined grains, snacks, high-energy drinks, mayonnaise and sweets.

    Semen samples were also collected from the men over an 18-month period following their dietary assessment. Both sperm count and the size and shape of the sperm and whether they moved normally were evaluated by computer-aided semen analysis (CASA).

    A total of 338 semen samples collected from 155 men between 2007 and 2012 were used in the analysis. Fifty-seven men contributed one sample, 51 men provided two samples, and 47 provided three or more semen samples.

    Using statistical methods, the researchers analysed the association between pesticide intake from fruit and vegetables with sperm count and quality.

    They adjusted their findings for other factors known to affect male fertility, such as age, smoking status, weight, periods of sexual abstinence, exercise, dietary patterns, and history of varicose veins (variocele) in the testicles.

    What were the basic results?

    The researchers found that:

    • the men's total fruit and vegetable intake was unrelated to their semen quality
    • high pesticide residue fruit and vegetable intake was associated with poorer semen quality
    • on average, men in the highest quartile of high pesticide residue fruit and vegetable intake, with 1.5 or more servings a day, had a 49% (95% confidence interval [CI] 31 to 63) lower total sperm count and a 32% (95% CI 7 to 58) lower percentage of normally shaped sperm than men in the lowest quartile of intake (0.5 servings a day)

    How did the researchers interpret the results?

    The researchers say their findings suggest that exposure to pesticides used in agriculture through diet may be sufficient to affect the quality and amount of sperm in humans.

    Conclusion

    Whether pesticide exposure in the diet is linked to male fertility problems is an important issue, but, as the authors point out, there are several reasons to view the results of this trial with caution:

    • the men were all attending a fertility clinic with their partner, so some of them will have had fertility issues unrelated to their diet or lifestyle
    • they used national surveillance data, rather than looking at individual diets, to assess how much pesticide residue the men had consumed
    • they did not have information on whether the men were eating organic or non-organic food
    • the men had to remember and report on their diet over the previous year, which could affect the reliability
    • their diets were only assessed once, which might have led to misclassification, and diets could change over time

    Male fertility can be affected by several factors. Although the researchers tried to adjust their findings for these, it is always possible that both measured and unmeasured confounders affected the results. Further studies looking at this important topic are needed.

    Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

    Links To The Headlines

    Pesticide residues on some fruit and vegetables harming men's fertility, study claims. The Independent, March 31 2015

    Pesticide in fruit and veg could harm man's fertility: Men who eat high levels have half the sperm count of those who ate the least. Mail Online, March 31 2015

    Could switching to organic fruit and veg double sperm count? The Daily Telegraph, March 31 2015

    Links To Science

    Chiu YH, Afeiche MC, Gaskins AJ, et al. Fruit and vegetable intake and their pesticide residues in relation to semen quality among men from a fertility clinic. Human Reproduction. Published online March 30 2015



  • Meningitis B jab to be added to NHS child vaccine schedule

    "All babies in the UK will soon have a potentially life-saving vaccine against meningitis B," The Guardian reports. The vaccine, Bexsero, will soon be offered to babies once they reach the age of two months, followed by two more booster shots.

     

    What is meningitis B?

    Meningitis B is a highly aggressive strain of bacterial meningitis that infects the protective membranes surrounding the brain and spinal cord. It is very serious and should be treated as a medical emergency. If the infection is left untreated, it can cause severe brain damage and infect the blood (septicaemia). In some cases, bacterial meningitis can be fatal.

     

    How common is meningitis B?

    The charity Meningitis Now estimates that there are 1,870 cases of meningitis B each year in the UK. Meningitis B is most common in children under five years old, particularly in babies under the age of one.

    Initial signs and symptoms of meningitis B in babies include:

    • a high temperature with cold hands and feet
    • they may feel agitated, but not want to be touched
    • they may cry continuously
    • some children are very sleepy and it may be difficult to wake them up
    • they may appear confused and unresponsive
    • they may develop a blotchy red rash that does not fade when you roll a glass over it

    For more information, read about the signs and symptoms of serious illness in babies.

     

    Why is this meningitis B vaccine in the news?

    The development of a safe and effective meningitis B vaccine is the culmination of more than 20 years of research and represents a significant breakthrough in disease prevention.

     

    What do we know about the vaccine?

    The vaccine, Bexsero, is thought to provide 73% protection against meningitis B, which should significantly reduce the number of cases. The vaccine can be administered to infants aged two months or older either by itself, or in combination with other childhood vaccines.

    The vaccine has been tested in clinical trials involving more than 8,000 people.

    In infants, it was found to have similar levels of safety and tolerability as other routine childhood vaccines. The most commonly reported side effects were:

    • redness and swelling at the site of the injection
    • irritability
    • fever

    It is thought that the vaccine will become available on the NHS in the autumn.

     

    Edited by NHS Choices. Follow Behind the Headlines on Twitter.

    Links To The Headlines

    Meningitis B vaccine added to UK child immunisation scheme. The Guardian, March 29 2015

    Now babies WILL get £20 meningitis jab. After year-long row over cost, NHS gives it the nod. Mail Online, March 30 2015

    Meningitis B vaccine deal agreed. BBC News, March 30 2015

    Every baby to be vaccinated against meningitis B in world first protection programme. Daily Express, March 30 2015

    Links To Science

     



  • Parents fail to spot that their kids are obese

    "Parents hardly ever spot obesity in their children, resulting in damaging consequences for health," BBC News reports after a new study found a third of UK parents underestimated the weight of their child.

    The study asked parents for their views about whether their child was underweight, a healthy weight, overweight or obese, comparing this with objective measurements of the child's weight and height taken on the same day.

    Researchers found most parents were only likely to think a child was overweight when they were at the top end of the very overweight category.

    The study was large, with almost 3,000 participants, but may not be representative of all parents in the UK, as many of those asked did not participate.

    The study also cannot tell us why parents are not recognising when their child is overweight, or the best and most effective way of improving this. But it does suggest that some help is likely to be needed to make sure parents know when their child is overweight.

    If you are concerned your child may be overweight, it is better to act quickly. Research suggests obesity in the teenage years tends to persist into adulthood.

    Read more advice about obesity in childhood

    Where did the story come from?

    This study was carried out by researchers from the London School of Hygiene and Tropical Medicine, the University of Bristol, University College London, and Imperial College London, and was funded by the National Institute for Health Research.

    It was published in the peer-reviewed British Journal of General Practice. One of the researchers received funding from the National Institute for Health Research.

    The UK media generally reported the findings of the study accurately. They also speculated about the causes of the discrepancy. The Telegraph and BBC News, for example, suggested that being overweight is now "the norm", making it hard for parents to tell when their children are not a healthy weight.

    "Society as a whole has become so fat we have collectively lost our sense of a healthy weight," said the BBC. But while the authors of the study do discuss possible reasons, the study did not directly assess whether these explain the discrepancy. 

    What kind of research was this?

    This was a cross-sectional study that compared parents' perceptions of their child's weight with objective measurements taken by school nurses. The researchers looked at how far the parents' assessments agreed with the objective assessments.

    National figures show one-third of children in England aged 10 and 11 were overweight or very overweight in 2012-13. Overweight children have a higher chance of getting serious health problems such as type 2 diabetes in later life.

    Previous studies showed only about half of parents can identify when their child is overweight. The researchers wanted to know at what point parents thought a child was overweight and what factors might affect this. The study didn't assess why people might wrongly estimate their children's weight. 

    What did the research involve?

    Every year, children in reception class (aged 4 to 5) and year 6 (aged 10 to 11) at state schools in England have their height and weight measured. This information was used to classify the children's weight against national standards.

    Researchers sent questionnaires to the parents of children from five primary care trusts in England who were being measured in 2010-11. They asked the parents to estimate whether their child was underweight, a healthy weight, overweight, or very overweight.

    They then compared the results of the children's measurements with what the parents thought, and looked for factors that were linked to their likelihood of estimating the child's weight correctly.

    The children's weight and height was converted into body mass index (BMI) and then compared with reference measurements taken from British children from 1978 to 1990.

    These measurements are organised in order of increasing BMI and split into 100 groups, or centiles, of increasing BMI, each containing 1% of the reference measurements. This shows the distribution of BMI for children at different ages and is the standard way of categorising child weight.

    Children are categorised as underweight if their BMI is at or below the 2nd centile, a healthy weight if they are between the 2nd centile and the 85th centile, overweight at or above the 85th centile, and very overweight (obese) if they are at or above the 95th centile.

    Researchers took the objective category for each child and compared it with the parents' assessment. They then looked at what point parents would be likely to categorise a child as underweight or overweight.

    They also looked at the children's age, sex, ethnic group, school year and the local area's levels of deprivation to see if they could identify factors associated with parents being more or less likely to underestimate or overestimate their child's weight status.

    Because so few parents categorised their children as being very overweight (obese), the researchers combined the very overweight and overweight groups for some of their calculations. 

    What were the basic results?

    Using the four categories of underweight, healthy weight, overweight, or very overweight, 68% of parents correctly categorised their child. Few parents (less than 1%) overestimated their child's weight status, but 31% underestimated it, believing them to be a healthy weight or even underweight when they were actually overweight or very overweight.

    Only four parents described their child as being very overweight, although the objective measurements placed 369 children in that category. Parents only became more likely to categorise a child as overweight rather than a healthy weight once the child was at the extreme end of the spectrum: at or above the 99.7th centile of BMI for their age.

    As an example, a child at the 98th centile, which is classed as very overweight according to national standards, had an 80% chance of being seen as a healthy weight by their parents, and only a 20% chance of being seen as overweight or very overweight.

    There were similar findings for the underweight category, with parents only becoming more likely to categorise a child this way if they were at the extreme end of the spectrum (under the 0.8th centile), compared with under the 2nd centile national threshold.

    The researchers said parents were more likely to underestimate their child's weight status if the children were black, south Asian, male, or older (in year 6 rather than reception). Families from better-off areas were less likely to underestimate their child's weight status.  

    How did the researchers interpret the results?

    The researchers concluded there is "extreme divergence" between the parents' estimation of their child's weight status and their categorisation according to their BMI.

    They say parents who are "unable to accurately classify their own child's weight" may be less likely to be "willing or motivated" to make changes at home that could help the child to reach and maintain a healthy weight.

    The researchers suggest some reasons for the discrepancy between parents' estimates and the medical assessments, including fear of being judged and unwillingness to label a child as overweight, as well as "shifting perceptions of normal weight" because society as a whole has seen an increase in body weight.

    They say there's a need for measures to bridge the gap between parents' perceptions of a child's weight status and the BMI categories used by medical professionals.

    Conclusion

    This study found parents in the UK are much less likely to think their child is overweight or very overweight than standard childhood BMI categories suggest. It also found parents of black or south Asian children, boys, and those from more deprived areas are more likely to underestimate their child's weight status.

    But this research has some limitations. While it is based on a fairly big sample size (2,976 children who had completed parental questionnaires stating their estimated weight classification and objective weight measurements), only 15% of the parents contacted actually sent back the questionnaire, and not all of them answered the question about weight status.

    This means we cannot be sure that these children are representative of all the children in the areas selected for the study (Redbridge, Islington, West Essex, Bath, and North East Somerset and Sandwell). Therefore, these findings may not be representative of all parents in those areas or other areas in the UK.

    There is also some debate about the most appropriate ways to measure being overweight or obese. Research from 2014 suggests using the BMI method (where weight is compared to height) is less accurate with children than with adults. 

    Although researchers looked for factors affecting the parents' estimates, including ethnicity and measures of deprivation of the local area, they did not look at other factors that might also be related to parental perception – for example, the parents' own weight status, anything about the family diet, or the amount of exercise the children got. This limits the conclusions that can be drawn from the study.

    While the authors discussed some possible reasons for the discrepancy between parents' estimates and the objective assessments, the study did not assess this directly, so we can't be sure what those reasons are. The study can't tell us why, for example, parents of boys or south Asian children are less likely to recognise that their child is overweight.

    And we don't know if the problem is restricted to parents, or whether other professionals, such as teachers and nurses, would also underestimate a child's weight status. It's even possible that parents might not recognise that their own child is overweight, but would be able to spot it in other people's children.

    It is a concern that parents don't recognise their children's weight problems – we know these children are at a higher risk of getting health problems in later life.

    The authors note that a 2011 Cochrane review suggested parental support could be one important part of bringing about lifestyle changes at home and reducing childhood obesity.

    Helping parents gain a better understanding of what a healthy weight looks like in a child could help reduce this problem and help improve children's long-term health.

    If you're concerned your child may be too heavy, ask your GP to check whether they weigh more than they should for their age. The good news is that teaching them about healthy eating and regular exercise can lead to weight loss, as well as instilling healthy habits that may persist into adulthood. 

    Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

    Links To The Headlines

    Parents rarely spot child obesity. BBC News, March 30 2015

    Obesity: parents unable to recognise if child is overweight. The Guardian, March 30 2015

    Just one in 100 parents spot obesity in their children. The Daily Telegraph, March 30 2015

    Parents fail to see that their own children are fat. The Times, March 30 2015

    Parents 'do not recognise their own child's obesity'. ITV News, March 30 2015

    Links To Science

    Black JA, Park M, Gregson J, et al. Child obesity cut-offs as derived from parental perceptions: cross-sectional questionnaire. British Journal of General Practice. Published online March 30 2015



  • Fit middle-aged men have lower cancer risk

    "Very fit men in their late 40s are less likely to get lung cancer and colorectal cancer than unfit men," says BBC News as it reports on a new US study.

    The study involved a comprehensive fitness test of 13,949 US men. They were split into three fitness groups: lowest 20%, middle 40% and top 40%, and followed for an average of 6.5 years to see if fitness affected their chance of developing certain cancers.

    Men in the fittest group were 55% less likely to develop lung cancer and 46% less likely to develop colorectal cancer compared with men in the lowest fitness group.

    Perhaps surprisingly, men in the top group actually had a 22% higher risk of prostate cancer.

    One obvious point is that men who exercise to stay fit are usually healthy in other ways too, such as eating a healthy diet and abstaining from alcohol. This could have influenced the results.

    Still, there is evidence that exercise alone can reduce your cancer risk. Information provided by Cancer Research UK explains how exercise can reduce inflammation and prevent bowel damage, which may reduce cancer risk.

    With its proven effect of preventing heart disease, regular exercise is always a good idea, whatever your age or sex. Read more about the benefits of exercise

    Where did the story come from?

    The study was carried out by researchers from the University of Vermont, the University of Texas Southwestern Medical Center, Duke University Medical Center in Dallas, and the Memorial Sloan Kettering Cancer Center in New York.

    It was funded by the US National Institute of General Medical Sciences, the National Institutes of Health, and the National Cancer Institute.

    The study was published in the peer-reviewed science journal JAMA Oncology. It was published as an open-access article, meaning it is free to read and download online.

    Generally, the UK media reported the story accurately, but none mentioned the possibility that diet could be accounting for some of the improvements seen, not just fitness.

    What kind of research was this?

    This was a longitudinal study looking at whether cardiorespiratory fitness (having both a healthy heart and lungs) prevents or improves outcomes in cancer.

    It used data already collected as part of the long-running Cooper Center Longitudinal study.

    There are many risk factors for cancer, including age, diet and physical activity. This study focused on fitness and whether this helped men develop fewer cancers, and survive better if they did develop cancer.  

    What did the research involve?

    The research analysed fitness data on 13,949 US men collected as part of the Cooper Center Longitudinal study between 1971 and 2009.

    The men were split into three fitness groups: lowest 20%, middle 40% and top 40%, and followed for an average of 6.5 years to see if fitness levels affected their chance of developing lung, colorectal or prostate cancer.

    Fitness was assessed using an incremental treadmill test, which tests a person's ability to run to exhaustion.

    The outcomes researchers were most interested in studying were:

    • new cases of prostate, lung and colorectal cancer 
    • death from any cause for men developing cancer over the age of 65
    • cause-specific death, such as cardiovascular disease, for men developing cancer over the age of 65

    Cancer diagnosis and notification of death came from Medicare claims data, which is the US government health insurance system covering people over 65.

    The statistical analysis took account of many common cancer risk factors, but not diet or the stage of cancer at diagnosis.

    The confounding factors adjusted for included:

    • age
    • examination year
    • body mass index (BMI)
    • smoking
    • total cholesterol level
    • systolic blood pressure
    • diabetes mellitus
    • fasting glucose level  

    What were the basic results?

    Over the study period, 181 men were diagnosed with colon cancers, 200 with lung cancers, and 1,310 with prostate cancers.

    The main message from the results is that exercise is very good at reducing the risk of developing lung and colorectal cancer, as well as helping reduce the risk of dying from cancer or cardiovascular disease. The pattern of risk for prostate cancer was less clear. 

    Men in the fittest group were 55% less likely to develop lung cancer (hazard ratio [HR] 0.45; 95% confidence interval [CI], 0.29 to 0.68), and 46% less likely to develop colorectal cancer (HR, 0.56; 95%; CI, 0.36 to 0.87), compared with men in the lowest fitness group. The risk of prostate cancer was actually 22% higher (HR 1.22; 95%; CI, 1.02 to 1.46).

    Similar benefits were seen comparing the middle exercise group with the lowest exercise group, but the risk differences were slightly smaller.

    For example, risks were 43% lower for lung cancer and 33% lower for colon cancer compared with the lowest fitness group. This time there was no difference for prostate cancer. This analysis covered cancers diagnosed at any age.

    Looking only at cancers diagnosed after the age of 65, the fittest group were 32% less likely to die from cancer compared with men in the lowest fitness group (HR, 0.68; 95%; CI, 0.47 to 0.98) – this included prostate cancer.

    They were also 68% less likely to die from cardiovascular disease after a cancer diagnosis (HR, 0.32; 95%; CI, 0.16 to 0.64) compared with the least fit men. 

    How did the researchers interpret the results?

    The authors concluded that, "There is an inverse association between midlife CRF [cardiorespiratory fitness] and incident lung and colorectal cancer, but not prostate cancer. High midlife CRF is associated with lower risk of cause-specific mortality in those diagnosed as having cancer at Medicare age [over 65]." 

    Conclusion

    This study shows that cardiovascular fitness is likely to reduce men's chances of developing lung and colorectal cancer, and appears to boost survival from cancer or cardiovascular disease in those diagnosed after the age of 65. This was based on comparing the top 40% of fittest men with the 20% least fit.

    The study focused on fitness and took account of major risk factors for cancer, such as smoking and blood pressure. However, it left out one important risk factor: diet. What people eat and drink is known to affect cancer risk.

    The fittest group may also have been the healthiest in terms of eating well and drinking alcohol within safe limits. This probably accounted for some of the risk reductions seen in this study. What proportion? We don't know. 

    This, in effect, makes this a study of healthiness incorporating fitness and diet. The evidence that eating well and being active reduces the risk of cancer, heart disease, stroke and diabetes is already well established. Studies have also shown regular physical activity also benefits our mental health.

    Read more about reducing your cancer risk.

    Although fitter men over the age of 65 diagnosed with cancer had better survival rates, there are other unmeasured factors that could have contributed. It is not known whether the fitter people were diagnosed with cancer at an earlier stage, which would have increased their chance of survival.

    There was also a counterintuitive finding worth noting. The fittest group were more likely to be diagnosed with prostate cancer than the least fit. This is important, as prostate cancer risk was much higher than lung or colon cancer in the sample.

    The study authors thought this might be because fitter men go for more cancer tests in the US than unfit men, so therefore the cancer is discovered and diagnosed more often in that group.

    It could also be the case that men in the fittest group would probably live longer, and prostate cancer is an age-related disease.

    But we don't know this for sure, and there could be other explanations worth investigating.

    Would you know if you had prostate cancer? Read more about prostate cancer symptoms.

    Analysis by Bazian. Edited by NHS ChoicesFollow Behind the Headlines on TwitterJoin the Healthy Evidence forum.

    Links To The Headlines

    Fit middle-aged men 'at lower risk for some cancers'. BBC News, March 27 2015

    Keep fit to beat cancer: Looking after yourself in middle age boosts men's chances. Daily Mirror, March 27 2015

    Keeping fit helps men with cancer to boost survival chances by a third. The Times, March 27 2015

    Links To Science

    Lakoski SG, Willis BL, Barlow CE, et al. Midlife Cardiorespiratory Fitness, Incident Cancer, and Survival After Cancer in Men - The Cooper Center Longitudinal Study. JAMA Oncology. Published March 26 2015