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NHS Choices: Behind the headlines   + / -  
last updated: Fri, 20 Jan 2017 14:47:16 GMT

 Thu, 19 Jan 2017 16:30:00 GMT Sitting down all day 'may accelerate DNA ageing'

"Women who lead a sedentary lifestyle have faster-ageing cells than those who exercise every day," BBC News reports.

This research looked at telomeres – often likened to the caps at the end of shoelaces, they are made up of molecules that protect strands of chromosomes from "fraying".

Telomeres shorten every time the genetic information in cells is duplicated. It's believed that this leads to cell ageing and death.

In a sample of older women, the researchers looked at whether there was an association between time spent sitting down and telomere length.

Telomeres are measured in the small sections of nucleic acids that make up DNA, known as base pairs. 

Among women in the study who did less than about 40 minutes of physical activity a day, those who sat longest had shorter telomeres by an average 170 base pairs.

The researchers say telomeres shorten at a rate of 21 base pairs a year – using a rough "back of a fag packet" calculation, 170 equals about eight years.

Sitting time did not seem linked to telomere length for women who did at least 30 minutes of physical activity a day.

We don't know whether the results apply to men or younger people.

And, importantly, as the study only looked at the women's activity levels and telomeres at one point in time, we don't know whether activity levels or sitting causes telomeres to shorten.

Still, arguably, most of us would benefit from spending less time sitting down.

Where did the story come from?

The study was carried out by researchers from the University of California, San Diego State University, the State University of New York at Buffalo, the University of Washington, the Fred Hutchinson Cancer Research Centre, George Washington University, the University of Florida and Northwestern University, all in the US.

It was funded by the US National Heart, Lung and Blood Institute. 

The study was published in the peer-reviewed American Journal of Epidemiology on an open access basis, so it's free to read online.

All of the UK media outlets that covered the study implied that a direct cause and effect relationship between sitting down and cell ageing had been proven.

For example, the Mail's headline stated that, "Women who spend at least 10 hours on their backsides each day speed up their aging process."

This is untrue. While there certainly seems to be an association worthy of further research, no causal link has been established.

What kind of research was this?

This cross-sectional study used data from women taking part in a much bigger study of health called the Women's Health Initiative.

Cross-sectional studies can find correlations between different factors – in this case, sitting time and telomere length.

But because this type of study only looks at one point in time, researchers can't say which factor happened first, so it's not very useful for telling us whether one causes the other.

What did the research involve?

Researchers used information about 1,481 women aged over 65 who'd taken part in various sub-studies of the Women's Health Initiative.

They used information from women who'd had their physical activity measured using accelerometers (devices that measure movement) and had also given DNA samples that had been tested for telomere length.

After accounting for other factors, they looked at whether telomere length was linked to the amount of time spent sitting.

The information about physical activity was measured over one week, during which time women wore their accelerometer all the time, except when bathing or swimming.

Women taking part also completed a questionnaire about their physical activity and kept a record of their sleep. Telomere length was measured from DNA in blood cells.

The researchers took account of the following possible confounding factors:

  • age and ethnic background
  • education level
  • marital status
  • smoking and alcohol consumption
  • body mass index
  • hours of moderate to vigorous physical activity each day
  • long-term diseases
  • use of hormone medicines

They also redid their calculations to divide the women into those who did more or less than the average amount of physical activity (about 40 minutes).

They then looked at the link between time spent sitting and telomere length for women who did more or less than 40 minutes physical activity a day.

They also looked at the link between sitting and telomere length for women who did 30 minutes or more a day, the recommended activity level for all adults.

It's unclear whether these additional calculations were planned from the start of the study, or whether the researchers decided to do them because the initial findings did not show a link between time spent sitting and telomere length.

What were the basic results?

The length of time spent sitting was not linked to telomere length for women who did 30 minutes or more of moderate physical exercise a day.

For women who did less than the average amount of moderate physical activity each day, time spent sitting did show a link to telomere length.

Among these women, those who spent more than about 10 hours a day sitting had shorter telomeres than those who spent less than about eight hours a day sitting. The average difference was 170 base pairs (95% confidence interval [CI] 4 to 340).

Women who spent the most time sitting were more likely to be older, white, obese and have long-term illnesses.

How did the researchers interpret the results?

The researchers said their results suggest that, "Prolonged sedentary time and limited engagement in moderate to vigorous physical activity may act synergistically to shorten leukocyte telomere length among older women."

In other words, being both sedentary for long periods and not getting much physical activity may act together to shorten telomeres in blood cells.

They speculated that causes of the link might include insulin resistance, lack of the anti-inflammatory responses the body has to exercise, or obesity.

They also acknowledged women who have long-term illnesses are more likely to have a sedentary lifestyle, and the illness rather than the lack of exercise may cause shortened telomeres.

Conclusion

It's not news to anyone that being more physically active and spending less time sitting around is likely to keep people in better health.

But this study has many limitations that make it difficult for us to rely on its results.

While they are used as a marker for ageing cells, telomeres are not a direct measure of ageing. Although shortened telomeres have been linked to certain diseases, everyone's telomeres shorten over time.

Saying shorter telomeres make someone "biologically older" doesn't mean much. This hasn't stopped the emergence of private companies offering to measure your telomeres – but it's unclear what exactly you could usefully do with that information. 

And the only cells studied in this research were blood cells, so we don't know whether the results would have held for brain cells, muscle cells or any other cells in the body.

Doctors have tried to disentangle the effects of physical activity from the effects of being sedentary before without much success.

Generally, as in this study, research seems to show that if you get plenty of moderate to vigorous physical exercise, the amount of time you spend sitting or lying down doesn't make much difference.

The researchers carried out a lot of comparisons and used multiple models to try to show sedentary time was linked to telomere length.

In most of these models, once you take account of women's age, ethnicity, body mass index and long-term illnesses, there was no link.

Only when the researchers stratified the results by how much physical activity women did could they show a link in one category: those who did the least physical activity.

That suggests sedentary behaviour is not the strongest factor to affect telomere length.

Another problem with the study is it only looked at telomere length and physical activity at one point in the women's lives.

We don't know how much physical activity they'd done throughout their lives, or whether their telomeres had shortened faster than other women recently or at an earlier stage in life.

The study doesn't add much to what we already know: physical activity is likely to be beneficial for people at all stages of life, and everyone should aim to get at least the recommended level of 30 minutes of moderate to vigorous physical activity a day.  

Links To The Headlines

Sedentary lifestyle in older women 'ages body cells'. BBC News, January 19 2017

Sitting down makes you age by 8 YEARS: Women who spend at least 10 hours on their backsides each day speed up their aging process. Daily Mail, January 18 2017

Sitting down for too long can speed up ageing, finds new study. The Independent, January 18 2017

Sitting down for hours a day speeds up ageing - new research. The Daily Telegraph, January 18 2017

Sitting down for 10 hours a day ages women by up to EIGHT years. Daily Mirror, January 18 2017

Links To Science

Shadyab A, Macera CA, Shaffer RA, et al. Associations of Accelerometer-Measured and Self-Reported Sedentary Time With Leukocyte Telomere Length in Older Women. American Journal of Epidemiology. Published online January 18 2017

 Wed, 18 Jan 2017 17:00:00 GMT A third of adults treated for asthma 'may not have the disease'

"The great asthma myth: A third of those diagnosed don't have the condition," reports the Mail Online.

A study in Canada found about one-third of adults diagnosed with asthma in the past five years showed no signs of the condition on retesting.

Asthma has become a common condition, and can cause serious illness or death if not treated. But symptoms come and go, meaning it's not always easy to diagnose reliably.

This study found people whose asthma could not be confirmed, despite a recent diagnosis, were less likely to have had objective tests of their lung function.

About one-third were able to safely stop taking asthma medicines under medical supervision.

In the UK, guidelines recommend doctors use spirometry tests in patients with symptoms that might be asthma when the doctor is not sure. A spirometer is a device that measures how much air you can breathe out of your lungs.

New guidelines on the best tests for asthma are being developed, but doctors are currently advised to start patients on treatment right away if there is a high likelihood of asthma based on their symptoms.

If you're not sure whether you need to continue taking asthma medication, talk to your GP.

It's not advisable to cut down asthma medicine or stop it suddenly without medical supervision, as asthma attacks can be serious.

Read more about asthma

Where did the story come from?

The study was carried out by researchers from the University of Ottawa, the University of British Columbia, the University of Manitoba, the University of Toronto, Université de Montréal, the University of Calgary, McMaster University, Dalhousie University, the University of Alberta and Université Laval, all in Canada.

It was funded by the Canadian Institutes of Health Research.

The study was published in the peer-reviewed Journal of the American Medical Association (JAMA).

The Mail Online criticised doctors for diagnosing asthma "without doing the proper tests", and repeated claims made last year that inhalers were being "dished out like fashion accessories".

However, spirometry is not a definitive test for asthma. It can miss cases (a false negative result) or suggest someone has asthma when they don't (a false positive).

Doctors are therefore currently advised to use their clinical skills as well as tests. 

What kind of research was this?

This cohort study recruited adults with a recent diagnosis of asthma and tested them repeatedly for asthma.

Researchers took people with no signs of the illness off medication and followed them for a year to see what happened. They also investigated how the patients had been diagnosed.

Cohort studies can find patterns – such as a link between asthma tests at diagnosis and the result of later retesting – but cannot prove that someone who didn't have a spirometry test at diagnosis did not have asthma, for example.

What did the research involve?

Researchers contacted thousands of people from 10 Canadian cities, asking if they'd had a diagnosis of asthma in the past 10 years.

Those who had and agreed to take part in the study were given a series of tests to confirm their diagnosis.

People whose tests didn't show signs of asthma were assessed by a lung specialist. Those who still had no signs of asthma had their medication reduced over time and, if appropriate, stopped.

They were then followed up for a year to see whether their symptoms worsened, and had two asthma tests during the year.

The first asthma test was spirometry, which measures how much air people can breathe out in one second. The test is then repeated after taking a puff from an asthma inhaler to see if that improves the results.

If it does, this indicates people have reversible airflow obstruction (reversible by medication), a key sign of asthma. If people had a negative spirometry test, they went on to further tests.

The researchers used a bronchial challenge test, in which people breathe in a chemical called metacholine that causes the airways to narrow. They then had spirometry to see how much the airways are affected at different doses.

If people did not have signs of asthma on this test, they had their dose of asthma medicine halved and were then retested after three weeks.

If those tests were normal, they stopped taking medicine altogether and were tested after another three weeks.

People who had no signs of asthma on any test then saw a lung specialist to look for an alternative diagnosis, and were followed up with two further bronchial challenge tests after 6 and 12 months.

Researchers also contacted the doctors who'd diagnosed the people in the study and asked about the process they'd used, whether they'd ordered spirometry or other tests, and for the results of those tests.

The researchers analysed the results to see how many of the people in the study could have a diagnosis of asthma ruled out. They also looked for differences between people with and without confirmed asthma.

What were the basic results?

Of the 1,026 people eligible to take part in the study, 613 completed all the study assessments and had their diagnosis of asthma either confirmed or ruled out.

  • In total, 410 (67%) people had their diagnosis of asthma confirmed and 203 (33%) had asthma ruled out.
  • Only a third of people who had asthma ruled out were taking asthma medication on a daily basis, though 79.3% were taking asthma medication occasionally.
  • Half of those with a confirmed diagnosis used asthma medication daily and 90% occasionally.
  • Only 86 people had their asthma confirmed by the initial spirometry test. Some (28) weren't diagnosed by tests at all, but had their diagnosis confirmed by a specialist at the final consultation.
  • Alternative diagnoses for the 203 people who'd had asthma ruled out included rhinitis and acid reflux. But 61 people (27%) had no symptoms of breathing trouble at all. Twelve people had serious cardiovascular conditions that had been misdiagnosed.
  • People whose diagnosis was ruled out were more likely to have been diagnosed without undergoing spirometry tests than people whose diagnosis had been confirmed. Just 43.8% of people whose diagnosis was ruled out had undergone airways tests at diagnosis, compared with 55.8% of people whose diagnosis was confirmed.

How did the researchers interpret the results?

The researchers say their results show that either people were misdiagnosed, or their condition had got better between diagnosis and retesting.

They say the test results, including follow-up results, show asthma symptoms and test results do come and go.

However, the researchers say the study suggests that "misdiagnosis of asthma may occasionally occur in the community".

They say 24% of doctors didn't answer requests for information about diagnosis of their patients, so it's "impossible to determine whether the initial diagnostic workup [initial assessment by their doctor], and hence the initial diagnosis of asthma in these participants, were appropriate".

This means we don't know to what extent the results were down to diagnosis or natural fluctuations in asthma symptoms.

Conclusion

The study results show being diagnosed with asthma at one point in your life doesn't necessarily mean you need to take asthma medication forever.

This study has some limitations. It was carried out in Canada, where the health service is different and doctors may use different practices to diagnose asthma. That means we don't know if the results are applicable to the UK.

Also, many people invited to take part did not do so, which means the participants may not be representative of the general population of people with asthma.

Not all doctors provided records of diagnosis, so we don't know how many people actually had asthma tests.

A third of people without asthma were not taking daily medication anyway, which indicates that they did not have current symptoms of asthma.

UK guidelines suggest people should have their need for asthma medication checked regularly so they don't take more than they require to keep symptoms under control.

Some people may be able to decrease their doses and then stop taking medication completely with medical supervision.

But it's not something you should do without your doctor's advice, as asthma attacks can be dangerous.

While tests like spirometry can help doctors make a diagnosis, they're not foolproof.

The National Institute for Health and Care Excellence (NICE) is currently looking at its advice on the diagnosis of asthma, and is expected to make new recommendations about the use of tests. 

At present, spirometry is recommended for all people presenting with possible asthma. However, a normal result does not rule out asthma.

Further lung function tests, such as peak expiratory flow, are recommended to confirm the diagnosis and for monitoring purposes.

If you're unsure whether your asthma medication is helping or you don't know whether you need to take it anymore, talk to your GP.

They can ask you about your symptoms, offer tests, and help you decide how best to manage your condition.

Read more about living with asthma.   

Links To The Headlines

The great asthma myth: A third of those diagnosed DON'T have the condition, study finds. Mail Online, January 17 2017

One third of asthmatics may not have the condition, study suggests. The Daily Telegraph, January 17 2017

One in three people diagnosed with asthma do NOT have the condition, experts warn. Daily Mirror, January 17 2017

Third of those treated for asthma don't really have it. The Times, January 18 2017 (subscription required)

Links To Science

Aaron SD, Vandemheen KL, FitzGerald M, et al. Reevaluation of Diagnosis in Adults With Physician-Diagnosed Asthma. JAMA. Published online January 17 2017

 Wed, 18 Jan 2017 16:30:00 GMT Eating disorders in middle-aged women 'common'

"Eating disorders…affect a small but substantial number of women in their 40s and 50s," BBC News reports. While often regarded as a "disease of the young", a new survey suggests 3.6% of middle-aged women in the UK are affected by an eating disorder.

Researchers also looked at childhood, parenting and personality risk factors associated with the condition. They found that 15% of middle-aged women had experienced an eating disorder at some point in their lifetime, and 3.6% had one in the last 12 months.

A commonly reported disorder is what is known as "other specified feeding and eating disorder". This term describes cases where a person may not fit the precise pattern of eating disorders such as anorexia but they still experience significant distress due to an unhealthy psychological relationship with food.

The study found that all potentially harmful childhood life events such as child sexual abuse, death of a carer and parental divorce, were associated with the onset of eating disorders. However, the study can't prove that these factors caused the disorder.

The researchers hope this survey will highlight that when it comes to diagnosing eating disorders, health service provision for middle aged women could be improved.

Read more about the help available for people with eating disorders as well as advice for friends and family who may be worried about others.

 

Where did the story come from?

The study was carried out by researchers from several UK, US and Swedish institutions including University College London, Harvard Medical School and the Karolinska Institutet in Stockholm. It was funded by the National Institute of Health Research UK and the UK children's charity Wellchild.

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

BBC News provided a well-balanced report on the study.

In contrast, the Daily Mail's reporting was both confused and confusing. Its headline: "Divorce blamed as more middle-aged women are hit by eating disorders", would naturally lead readers to assume it is going through divorce is a risk factor. But the study only explicitly mentions parental divorce as a risk factor in childhood.

 

What kind of research was this?

This was a cross-sectional analysis which used data from an existing longitudinal study – the UK Avon Longitudinal Study of Parents and Children (ALSPAC) to investigate the prevalence of eating disorders in middle-aged women. Within this, the researchers explored childhood, parenting and personality risk factors associated with the condition.

Eating disorders are severe mental health problems which cause an individual to change their eating habits and behaviour. The conditions can affect someone physically, psychologically and socially.

Traditionally, these conditions are associated with younger women but the researchers recently identified a gap in access to healthcare for adults with eating disorders in a UK population. As a result, they wanted to investigate this further.

Observational studies like this one are useful for assessing the incidence and prevalence of health conditions. However the study design limits the ability to prove causation between exposure and outcome, for example, between a potential risk factor and the development of an eating disorder. 
 

What did the research involve?

The data for this analysis was obtained from ALSPAC, a population-based prospective cohort study of women and their children.  ALSPAC followed 14,541 pregnant women and examined the effects of environment, genetic and other factors on them and their children.

This analysis included a sample of 9,233 of the women (average age 48 years) and asked them to complete a version of the Eating Disorders Diagnostic Schedule (EDDS). The EDDS uses different criteria to diagnose the following conditions:

Women who were screened positive (5,655) based on the screening criteria were interviewed using the eating disorders section of the Structured Clinical Interview for DSM-IV-TR disorders (SCID-1).

The interview assessed presence, frequency and duration of behaviours associated with eating disorders such as restriction, fasting, excessive exercise, binge eating, and purging. The women were asked to relate any changes in their eating behaviours with major life events to see if they were potentially associated.

Data for 1,043 women on relevant predictors of the onset of eating disorders was obtained from the ALSPAC database collected 20 years prior to this analysis:

  • childhood unhappiness
  • parental divorce or separation, adoption or being under health authority care
  • death of a carer
  • early sexual abuse
  • life events
  • bonding with parents
  • locus of control (LOC ) – whether a person feels in control of their life
  • interpersonal sensitivity

The data was then analysed to search for any potential associations between risk factors and the onset of eating disorders.

Potential confounders such as maternal age, ethnicity and education were adjusted for.

 

What were the basic results?

Overall the researchers found 15% of middle aged women had experienced an eating disorder in their lifetime, and 3.6% had one in the last 12 months.

Anorexia nervosa was the most common specific lifetime disorder, with a prevalence of 3.6%, though the general category of "other specified feeding and eating disorder" was most common, affecting 7.6%.

Several links emerged between early risk factors and the onset of eating disorders:

  • Experiencing the death of a carer was associated with a seven-fold increase in odds for the onset of purging disorder (odds ratio [OR] 7.12; 95% confidence interval [CI] 2.32 to 21.85).
  • There were higher odds of suffering from bulimia nervosa (OR 2.02), binge eating disorder (OR 2.01) and anorexia nervosa (OR 2.49) following parental separation or divorce in childhood.
  • Child sexual abuse was associated with all disorders linked to binge eating behaviours: anorexia nervosa binge purge (OR 3.81), bulimia nervosa (OR 4.70) and binge eating disorder (OR 3.42).
    Sexual abuse from a non-stranger was linked with anorexia nervosa binge purge, bulimia nervosa and binge eating disorder.
  • Childhood unhappiness was associated with increased odds of anorexia nervosa (OR 2.52), bulimia nervosa (OR 4.58), binge eating disorder (OR 3.66) and purging disorder (OR 2.65).

Overall, all the childhood life events were positively associated with eating disorders, and the more life events there were, the higher the risk.

 

How did the researchers interpret the results?

The researchers concluded: "Although some risk factors differed across [eating disorder] subtypes, childhood sexual abuse and poor parenting were associated with binge/purge type disorders, whilst personality factors were more broadly associated with several diagnostic categories. Few risk factors were specifically associated with one diagnostic category."

 

Conclusion

This well-designed cross-sectional analysis used data from an existing longitudinal study to investigate the prevalence of eating disorders in middle-aged women and see what childhood, parenting and personality risk factors were associated with the onset of an eating disorder.

The research found that more than 1 in 10 middle aged women experience some form of eating disorder in their lifetime. It found that all potentially harmful childhood life events such as child sexual abuse, death of a carer and parental divorce, were associated with the onset of eating disorders.

An association with traumatic life events is definitely plausible, or even likely. However, it must be noted that within the context of observational survey data, such studies are never able to prove that any single exposure causes the development of an eating disorder.

This study has not been able to take into account all aspects of a person's mental and physical health, interpersonal relationships and lifestyle prior to the onset of an eating disorder. Therefore the study can show associations but cannot prove definite causation with any individual factor.

The researchers say that this research has implications for health service provision in the UK, which needs to recognise that women in mid-life can still be suffering from the effects of long-standing disorders, or be at risk of developing new disorders. Therefore better awareness of eating disorders and their symptoms is needed.

Dr. Agnes Ayton, Vice Chair of the Faculty of Eating Disorders, Royal College of Psychiatrists commented on the research saying:

"This is an important paper, which has several methodological strengths: it is population-based (rather than only including people who seek contact with health care, which is always the tip of the iceberg). It has used reliable assessment of the eating disorder, by interviewing with validated instruments, rather than relying on self-report. It was also able to identify risk factors, which were collected many years ago as part of the AVON Longitudinal Study, therefore avoiding recall bias.

"It demonstrates that the rates of eating disorders amongst middle age women are higher than it was thought, and that significant proportions of these people are unknown to services – so there is a large unmet need."

Find eating disorders support services in your local area.

Links To The Headlines

Eating disorders can strike in mid-life. BBC News, January 17 2017

Divorce blamed as more middle-aged women are hit by eating disorders: 15% have battled bulimia or anorexia. Daily Mail, January 17 2017

Rising number of middle-aged women are ‘battling anorexia and bulimia’, new figures warn. The Sun, January 17 2017

Eating disorders are hitting more women in middle age. Daily Mirror, January 17 2017

Study uncovers hidden epidemic of eating disorders in middle-aged women. The Daily Telegraph, January 17 2017

Links To Science

Micali N, Martini MG, Thomas JJ, et al. Lifetime and 12-month prevalence of eating disorders amongst women in mid-life: a population-based study of diagnoses and risk factors. BMC Medicines. Published online January 17 2017


 

 
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