Low-fat diets 'not the best way to lose weight'

Friday October 30 2015

Low-carb rather than low-fat may be the way to go

"Low-fat diets are not the best way to lose weight," the Daily Mail reports. The findings come from a new review that analysed data from more than 50 previous studies on low-fat dietary interventions involving almost 70,000 adults.

The study aimed to see how low-fat diets measured up to comparison diets for achieving long-term weight loss, defined as a year or more.

The findings were mixed. There was evidence from a large number of trials that low-carb diets were better for weight loss than low fat – helping to achieve 1.15kg more weight loss after one year.

However, low-fat diets still worked, and consistently resulted in about 5.41kg more weight loss than if the person continued with their usual diet.

But a potential limitation of this latest research is that the individual trials varied greatly in their study populations (many had varied chronic diseases), as well as the constituents of the low-fat and comparison diets, and the ways these diets were encouraged or monitored. 

Also, it is difficult to know how compliant people may have been to the diets they were assigned to. This makes it harder to tease out the specifics of the best diet, as many different methods were pooled to find the overall pattern. 

Losing weight through diet alone can be difficult. Regular exercise can increase your chances, as well as bring about other health benefits. 

The NHS Choices Weight loss plan provides both dietary and exercise advice that can lead to sustainable long-term weight loss.    

Where did the story come from?

The study was carried out by researchers from Harvard Medical School, Harvard School of Public Health, Brigham and Women's Hospital, and Boston Children's Hospital in the US. Funding was provided by the US National Institutes of Health and the American Diabetes Association, which had no role in the study.

One of the authors of the study reported receiving research support from the California Walnut Commission and Metagenics, a company that sells dietary supplements.

The study was published in the peer-reviewed medical journal, The Lancet Diabetes and Endocrinology.

While some of the headlines were somewhat simplistic, the UK media generally covered the new research accurately and gave good balance to the discussion. For example, the reporting included advice that guidance should perhaps focus on portion sizes and the need to limit processed foods, rather than focusing specifically on nutrient groups like fats, carbs or protein.

Coverage also included expert recommendations suggesting preventing weight gain in the first place by better informing people about healthy diet and exercise. Of course, you can do both, pursuing a long-term prevention strategy while doing your best to deal with the immediate consequences.  

What kind of research was this?

This was a systematic review that searched the literature to identify randomised controlled trials where people had been allocated to a low-fat diet or any comparison diet. The results of these studies were then pooled in a meta-analysis to look at the overall effects of low-fat diets.

The researchers discuss how the optimal nutrient balance of calories coming from fat, protein and carbohydrate to achieve long-term weight loss has been debated for decades.

Low-fat diets have been popular because of the far greater proportion of calories contained in fat, compared with the same weight of protein or carbohydrate.

However, the researchers say trials don't consistently show that low-fat diets actually achieve more long-term weight loss than other diets. This review therefore aimed to pool the evidence to see how different dietary interventions matched up against each other.

This review has strengths, as it only included randomised controlled trials, which are the best way of looking at the effectiveness of an intervention because the participants are randomly allocated to the diet. 

Studies of dietary patterns are often observational. While these can look at associations between diet and outcome, as the people choose the diet themselves, you can never be sure other health and lifestyle factors aren't influencing the outcome. 

What did the research involve?

This review searched literature databases for randomised controlled trials in adults comparing a low-fat diet with any diet of higher-fat contribution, including the person's usual diet. Only trials that measured long-term weight change over at least a year were included.

They excluded studies where the comparison arm was not a diet, such as exercise or weight-loss medication. They also excluded studies featuring dietary supplements or meal replacements, although studies that had additional dietary changes alongside the low-fat intervention (such as boosting fruit and veg intake) were allowed.

The main outcome examined was the average change in body weight from the study start to one year or greater.

A total of 53 trials, involving 68,128 adults, met the inclusion criteria, most of which (37) came from the US or Canada. Just over a third of the trials (20) included people with specific conditions or chronic diseases, including breast cancer, diabetes and heart disease. 

About two-thirds of the trials (35) had weight loss goals with the dietary intervention, but the remainder either had no weight loss target or were just aimed at weight maintenance. 

Most trials (27) were only one year in duration. However, it's not certain whether the interventions lasted this long, or just the follow-up.

The low-fat diets ranged from very low (≤10% calories from fat) to moderate fat intake (≤30% calories from fat). Comparison diets were varied and included moderate-to-high fat intakes, or other interventions, such as low carbohydrate.

The trials also varied in how they controlled the diets in their study. For example, some just gave instructions or information leaflets, while others actually provided the food. 

What were the basic results?

All 68,128 adults across all trial arms lost an average (mean) 2.71kg of weight after an average of one year follow-up. The average weight loss in the 35 trials that had weight loss goals was 3.75kg.

The pooled results of 18 trials found low-carbohydrate diets were more beneficial for weight loss than low-fat, resulting in an average 1.15kg greater weight loss (95% confidence interval [CI] 0.52 to 1.79kg). These were all diets with weight loss goals – no trials aimed at weight maintenance or no weight loss compared low-fat with low-carb diets.

Low-fat diets resulted in significantly greater weight loss compared with usual diet:

• eight trials with weight loss goals found an average 5.41kg (95% CI 3.54 to 7.29) greater weight loss with low-fat compared with usual diet
• 11 trials with no weight loss goal found 2.22kg (95% CI 1.45 to 3.00) greater weight loss with low fat
• three trials aiming at weight maintenance found 0.70kg (95% CI 0.52 to 0.88) greater weight loss with low fat   

There was no significant difference when comparing the weight loss achieved with low-fat compared with high-fat diets, regardless of weight loss goal.

Overall, when pooling all the trials, regardless of comparator, there was no significant difference in weight loss between the low-fat diet and the comparison arms in trials aiming at weight loss.

However, for the trials with weight maintenance or no weight loss goals, low-fat diets did result in significantly greater weight loss than the comparator (1.54 and 0.70 kg, respectively).  

How did the researchers interpret the results?

The researchers concluded that, "These findings suggest that the long-term effect of low-fat diet intervention on body weight depends on the intensity of the intervention in the comparison group.

"When compared with dietary interventions of similar intensity, evidence from RCTs [randomised controlled trials] does not support low-fat diets over other dietary interventions for long-term weight loss." 

Conclusion

This review has aimed to answer the question of whether low-fat diets result in any greater weight loss compared with other diets, as has often been speculated. It showed they didn't. Most diets worked, and the low-fat ones weren't particularly better than the rest.

The systematic review design has many strengths. It has identified a large number of studies, with almost 70,000 participants, all of which were randomised controlled trials. This should balance out any non-diet-related health and lifestyle characteristics between participants. It also only included trials of at least one year's duration to look at longer-term effects on weight loss.

However, it is worth taking time to consider the results before potentially jumping to the conclusion that a low-fat diet is of no benefit and eating as much fat as you like is a healthy option.

The review found no difference in the effect of a low-fat diet compared with a high-fat diet. But it did consistently find changing to a low-fat diet resulted in significantly greater weight loss when continuing with the person's usual diet, regardless of whether the person was trying to lose weight or not.

The review did, though, find evidence from a large number of weight loss trials to suggest low-carbohydrate diets may be of more benefit than low fat. Unfortunately, there were no trials available to see whether this held when no weight loss goal was intended, but it is possible the same effect may be seen regardless of aim.

But interpreting this – particularly if trying to inform someone of their likely weight loss when following a particular diet – is difficult when variations across the trials included are considered.

These were all randomised controlled trials – which is a definite plus point – but they were still diverse in many ways. The study populations varied greatly. For example, some included men or women, some just overweight or obese people, and others had people with varied chronic diseases or health conditions.

The components of the low-fat and comparator interventions, and the ways these diets were encouraged or monitored, was also very different across trials.

There are many unknowns. For example, what were the other constituents of these diets – such as fruit and vegetable intake – particularly when it was the person's usual diet? Also, were there any specifications about what types of fat where being eaten, whether saturated fats or even trans fats, or "healthier" mono- or polyunsaturated fats?

Because of the variability in the trials, it is difficult to give a definitive answer about whether a low-fat or low-carb diet is going to help any individual lose more weight. It is likely to be overall components of the diet, and the total energy intake balanced against physical activity, that has an effect.

To lose weight, essentially we need to take in less energy, in the form of calories, than the energy we're using up in daily activity. We need fats, carbohydrates and protein in our diet, and following a diet that completely cuts out one of these groups is unlikely to be beneficial to our health or help sustain a healthy weight in the long term. 

An important goal is finding a reduced calorie diet that you actually enjoy eating. That way, you are more likely to stick to it. A healthy dietary pattern should include lots of fruit and vegetables and lower amounts of sugar, salt and saturated fats, combined with regular exercise.

If you're looking to lose weight, try the NHS Weight loss plan.

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Exercise and therapy 'useful for chronic fatigue syndrome'

Wednesday October 28 2015

Graded exercise therapy is designed to slowly raise fitness levels

"ME can be beaten by positive thinking and taking more exercise," is the rather simplistic message from the Daily Mail following the results of a long-term study involving 481 people.

The study compared four types of treatment for chronic fatigue syndrome (CFS), a condition where people feel so persistently exhausted they cannot function, also called myalgic encephalomyelitis (ME). Researchers found positive results for two types of treatment lasted for at least two years.

A 2011 study comparing four commonly used treatments seemed to show two types of treatment worked better: cognitive behavioural therapy (CBT), a type of talking therapy that aims to help people challenge unhelpful thinking patterns, and graded exercise therapy (GET), where people are helped to gradually increase the amount of exercise they do each day.

The other treatments were specialist medical care (SMC) or adaptive pacing therapy (APT), where people are helped to pace their activities to avoid getting fatigued.

The researchers went back to the patients two years after the study began to see what happened next. They found those who had CBT and GET kept their initial levels of improvement, while those who had APT and SMC had improved since the end of the study year.

But, as the researchers themselves concluded, "Better treatments are still needed for patients with this chronically disabling disorder". 

Where did the story come from?

The study was carried out by researchers from the University of Oxford, King's College London, University College London, and Queen Mary University of London, and was funded by the UK Medical Research Council, the Department of Health for England, the Scottish Chief Scientist Office, the Department for Work and Pensions, and the National Institute for Health Research. 

One of the researchers declared a potential conflict of interest, as they have worked as a consultant for an insurance company. Two other authors declared they had written books that promote cognitive-based approaches to treating CFS/ME, which they continue to receive royalties for.

The study was published in the peer-reviewed The Lancet Psychiatry. It has been made available on an open access basis, which means it is free to read online.

Although they did report the overall study results, The Daily Telegraph and the Daily Mail focused on questions about whether CFS is a physical or mental illness, as well as the disagreements between the study author and the ME Association. They did not look closely at the study results. The study itself was a comparison of four types of treatment, so cannot answer questions about the nature of the illness.

The papers' headlines were also somewhat simplistic, suggesting the condition had been "beaten" or "overcome". While there was a reported improvement in symptoms, this certainly didn't amount to a cure. 

What kind of research was this?

This follow-up of a randomised controlled trial looked at what happened to the people who took part in the original trial after the study had finished.

Randomised controlled trials are the best way to compare different treatments. Follow-up after a study has finished can show us whether any benefits are lasting.

However, as the study had ended, we can be less sure about whether differences between treatment groups are the result of the treatment participants originally had, or if it was anything that happened since the study ended. 

What did the research involve?

In the original study, people with chronic fatigue syndrome were split into four groups. All were offered specialist medical care. In addition, one group had cognitive behavioural therapy (CBT), one group had graded exercise therapy (GET), and one group had adaptive pacing therapy (APT).

At the end of one year, each group was assessed to see whether their symptoms had improved. In this new research, the same groups were followed up at least two years after the original study started and answered the same questions about their symptoms.

Between the end of the one-year study and the follow-up questionnaires, people had been able to have additional treatment, choosing which therapies to try with input from their doctor. This means some people will have tried additional therapies, while others only received their original treatment.

The researchers carried out different analyses to see whether their results could have been changed by numbers of people not returning questionnaires, how long people took to return the questionnaires, how ill they were at the start of the study, and so on.  

What were the basic results?

The results of the original study found people who had CBT or GET had, on average, lower levels of fatigue and were able to function better physically at the end of the study year. The follow-up study showed these results persisted, so people in these groups either stayed the same or improved slightly after the first year.

People who had specialised medical care alone, or with APT, had less positive results at the end of the study year, although everyone improved somewhat. By the end of the follow-up, these groups had further improved for fatigue and physical functioning. The final results at the end of two or more years were about the same for people in each of the four groups.

More than half (63%) of those who received specialised medical care alone went on to have more treatment after the study finished, as did 50% of those who had APT. In the other two groups, 31% of people who had CBT and 32% of those who had GET went on to have more treatment. Most of the additional treatment received was CBT or GET. 

How did the researchers interpret the results?

The researchers say the most important result was that, "The beneficial effects of CBT and GET seen at one year were maintained at long-term follow-up" two or more years after the trial started. They say the improvements seen by people who originally had specialist medical care alone or with APT could have a number of causes.

It could simply mean these people got better with time, or their symptoms settled down from being very bad at the start of the study to average after two years. However, the researchers say the improvements could also be because by this time many of these people had now received CBT or GET.  

Conclusion

This study gives us the long-term results of the only randomised controlled trial to directly compare four commonly used treatments for chronic fatigue syndrome. It is encouraging that people who seemed to benefit from CBT and GET in the first year of the study were still seeing those benefits after another year.

The finding that people who had the other types of treatment – specialist medical care alone or with APT – improved during the year after the study had finished is interesting and difficult to interpret.

It could simply be the case that these people got better over time, although previous studies have shown people with chronic fatigue syndrome tend not to get better without treatment. It could also be because some of them had CBT or GET in the year following the study. But we simply don't know if this is the case.

The researchers say they carried out an analysis that did not show additional treatment was linked to higher chances of getting better. They warn this analysis was not reliable because it could not take account of other factors that might have affected the results. This is one of the study's main limitations.

Another limitation is that only 75% of people who took part in the original study returned their follow-up questionnaire, and the length of time between people finishing the study and sending back the questionnaire varied.

This study doesn't tell us anything about the cause of chronic fatigue syndrome, a much-debated cause for controversy. Some people think it is a physical illness caused by infection, while others think it may be more of a mental health condition or reaction, and could be an umbrella term for a number of different conditions. As the study mentions, there are around 20 different published case definitions of what chronic fatigue syndrome is.

What is not in doubt is chronic fatigue syndrome causes much suffering. At present, we don't know what causes it and there are no cures, though some people do fully recover. In the meantime, researchers, doctors and patients have to seek out the treatments that have the best evidence for effectiveness.

As the researchers themselves say, some people in this study didn't get any better, regardless of which treatment they had. We know CBT and GET don't help everyone, even if they seem to help more people than other currently available treatments. We still need better treatments for this complicated and disabling condition.

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Living near an airport 'may be bad for your health'

Wednesday October 21 2015

Aeroplanes waiting for takeoff can release a great deal of carbon monoxide

"People who live within six miles [of an airport] have higher levels of asthma and heart problems," the Daily Mail reports after a US study has suggested exposure to carbon monoxide from planes may impact on health. This potential pollutant is thought to occur when planes are taxiing on busy runways.

Researchers used data to look at the link between exposure to daily pollutants and health in areas close to the 12 biggest airports in California. Health outcomes were measured using data for overnight hospital admissions and emergency visits from residents within 10km of these airports.

An association was found between higher levels of carbon monoxide and increased hospitalisation rates for respiratory conditions such as asthma, as well as heart-related issues.

But this study is not able to prove cause and effect, and there may be other factors at play, such as higher levels of urbanisation in areas near airports.

Still, these findings are in line with other research, which suggests increased pollution levels are associated with poorer health outcomes. The results are likely to add fuel to the debate about whether Heathrow or Gatwick airports should be expanded with a new runway.

Where did the story come from?

The study was carried out by researchers from Colombia University and the University of California, and was supported by the Robert Wood Johnson Foundation. 

It was published in the peer-reviewed journal The Review of Economic Studies on an open access basis, so it can be downloaded free as a PDF.

This study has been reported accurately by the Daily Mail, but the paper does not note any of the study's limitations.  

What kind of research was this?

This data analysis study aimed to assess the link between variations in airport congestion and health outcomes related to daily carbon monoxide exposure, particularly respiratory conditions.

While this type of study can draw links for further investigation, it can't prove pollution was responsible for the health outcomes. However, it is important to note pollution is a known risk factor for respiratory and heart-related conditions.  

What did the research involve?

Air pollution and the link with respiratory and heart-related issues were investigated in the areas surrounding the 12 largest airports in California.

This study used a number of sources to obtain data for analysis for the period 2005-07. Airport traffic data was found in the Bureau of Transportation Statistics (BTS) Airline On-Time Performance Database, which contains flight information for passenger aircraft, such as departure and arrival times, and airports.

The measure of air traffic for 12 major airports in California consisted of:

• the time aeroplanes spend between leaving the gateway and taking off from the runway
• the time between landing and reaching the gate

Data for pollution around the airports was collected from the California Air Resource Board (CARB), which includes hourly and daily pollution readings.

The weather effects on health were controlled for in the analysis by using temperature, precipitation and wind data in distributing airport pollution from airports. Wind data was obtained from the National Climatic Data by the National Oceanic and Atmospheric Administration's (NOAA) hourly weather stations.

Health effects were measured using the California Emergency Department and Ambulatory Surgery data for emergency room visits, and inpatient discharge data for overnight hospital admissions. Daily admissions of all people with a diagnosis associated with respiratory illnesses were included.

Statistical modelling was performed to estimate a number of links, including:

• pollution levels and hospitalisation
• increased levels of airport traffic
• congestion and local measures of pollution
• health and air pollution  

What were the basic results?

The study found a large proportion of local air pollution is caused by congestion from airports, and the average area of impact is a 10km radius, with levels of carbon monoxide fading with distance. 

In terms of the link with health outcomes, admissions for respiratory problems and heart disease were strongly related to these pollution changes. A one standard deviation increase in area-specific pollution levels increased asthma counts by 17% of the baseline average.

It also increased admissions for respiratory problems, such as chronic obstructive pulmonary disease (COPD), by 17% and heart problems by 9%. Changes in pollution levels had a negative impact on the whole population, but greater effects were seen in children and the elderly.  

How did the researchers interpret the results?

The researchers concluded that, "Daily variation in ground level airport congestion due to network delays significantly affects both local pollution levels, as well as local measures of health."

They also stated that, "A one standard deviation increase in daily pollution levels leads to an additional $540,000 in hospitalisation costs for respiratory and heart-related admissions for the six million individuals living within 10km (6.2 miles) of the airports in California.

"These health effects occur at levels of carbon monoxide exposure far below existing Environmental Protection Agency mandates, and our results suggest there may be sizeable morbidity benefits from lowering the existing CO standard." 

Conclusion

This study aimed to assess the link between pollution from air traffic and health outcomes. Researchers used a number of data sources, finding an association between levels of carbon monoxide and hospitalisation rates for respiratory and heart-related issues.

Perhaps worryingly, these effects were observed at lower levels of carbon monoxide exposure than the allowed amounts found in Environmental Protection Agency mandates.

However, this study does have a number of limitations:

• Air traffic data was only from passenger aircrafts.
• The focus was only on the population within 10km of the airport. We don't know the levels of other pollution sources in the areas studied, or whether residents spend large amounts of time in other areas, either for work or study purposes, for example.
• The main sources of air pollution are traffic and industrial sources, such as factories.

These findings are in line with other research, however, which suggests increased pollution levels are associated with poorer health outcomes.

Air pollution is a known major risk factor for health, and ways to reduce levels should be investigated to reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma.

These findings might suggest policies may need to be reassessed worldwide to ensure the best possible health outcomes.  

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Modern sleep patterns 'mirror how our ancestors slept'

Friday October 16 2015

Complaints that technology disrupts sleep go back to Victorian times

"Forget eight hours of sleep a night – we only actually need six," the Daily Mail reports. Research into hunter gatherer tribes suggests getting six to seven hours sleep a night may not be a modern phenomenon and is actually the norm for humans.

An ongoing concern about modern life is our sleep patterns are being adversely affected by the distractions of modern technology, such as smartphones, tablets and TVs. But, as the authors of this research highlight, similar concerns can be found in popular media dating back to the Victorian era.

To get a clearer picture of "pre-industrial" sleep habits, researchers studied three hunter gatherer communities who had no access to any of the trappings of modern life. These people were members of the Hadza (northern Tanzania), San (Namibia), and Tsimane (Bolivia) tribes.

The researchers found the hunter gatherers' sleep patterns were to a certain extent similar to those of the West – getting an average of 5.7 to 7.1 hours' sleep a night.

Sleep patterns seemed to mirror the temperature more than light levels. This finding could potentially help people with sleep disorders. The US National Sleep Foundation recommends a bedroom temperature of 18.3C (65F).

Interestingly, chronic insomnia was uncommon among the tribespeople – around 2% of tribespeople, compared with 10-30% in industrial societies. Two of the tribes actually had no word for insomnia in their language. This may suggest an active lifestyle can help prevent insomnia. 

Where did the story come from?

The study was carried out by researchers from US universities, including academics from departments of anthropology, anatomical sciences, neurology and brain research, and psychiatry.

It was funded by US National Institutes for Health grants, the National Research Foundation of South Africa, and the National Science Foundation.

The study was published in the peer-reviewed journal Current Biology on an open-access basis, so it is free to read online or download as a PDF.

Headlines like the Daily Mail's – "Forget eight hours of sleep a night – we only actually need six" – and a similar headline in The Independent – "Six hours' sleep a night is enough, say scientists" – are not justified based on the results of this this study alone. The authors only studied sleep patterns. They make no recommendations about what sleep patterns are healthier.

Nonetheless, the Mail's statement that these "findings challenge [the] eight-hour rule" may be fair – a debate about the right amount of sleep is worth having, given the implications of this research. The next part of the sentence – "modern life is robbing us of sleep" – is largely subjective.  

What kind of research was this?

This was an observational study of the natural sleep cycles in three non-industrial communities. The researchers say it has been argued that the invention of electric lighting, TV, the internet and related gadgetry, along with more caffeine use, has greatly shortened sleep duration from the "natural" levels that occurred before these modern changes.

The authors state this may have health implications. They report sleeping less has been linked to obesity, mood disorders and a "host of other physical and mental health illnesses thought to have increased recently".

With this in mind, they sought to establish what "natural" sleep patterns might be without the distractions of modern lighting, heating and electronic gadgetry.

In the absence of good data on sleep patterns from the past, they studied three non-industrial societies who live largely as hunter gatherers near the equator: the Hadza (northern Tanzania), the San (Namibia), and the Tsimane (Bolivia).

Studying these modern but non-industrialised groups, they hoped, would give an idea of the type of sleep patterns our ancestors might have had before mass migration to cities and the technological revolution.

What did the research involve?

The researchers collected data from 10 groups within three geographically different societies.

Participants wore watches that tracked their activity for between six and 28 days. The watches had been tested and validated, so they were able to detect when people were awake or asleep, as well as information on exposure to sunlight (mainly used to detect day and night sleeping habits).

Environmental temperature was measured by different devices attached to the middle fingers of both hands and the abdomen for the first four days of observation. These were also placed near where the participants slept to collect data on the temperature and humidity of their sleep environment, both in winter and summer. 

On average, the participants were underweight or a healthy weight according to their body mass index (BMI). None of the people studied were overweight, a notable contrast to many industrialised societies.

The analysis looked at patterns of sleep onset and sleep duration in relation to light levels, seasons and temperature. Sleep onset is the length of time it takes to go from being fully awake to sleep – the "getting to sleep" phase.

Sleep duration is usually characterised by the time spent in either non-rapid eye movement sleep or rapid eye movement sleep, but in this study it was predicted based on how much people were moving, as detected by the watch. 

What were the basic results?

All three groups showed similar sleep patterns. Sleep period – time including getting to sleep, sleeping and fully waking up – averaged 6.9 to 8.5 hours, with time spent fully asleep averaging around 5.7 to 7.1 hours. These were described as amounts near the low end of those of industrial societies.

On average, people slept an hour more in winter time than summer. None of the groups started trying to sleep near sunset – they averaged 3.3 hours after. Most woke an hour or so before sunrise, although there were examples of some waking after sunrise.

Napping wasn't particularly common, occurring in less than 7% of days in winter and less than 22% of days in summer. 

How did the researchers interpret the results?

The researchers concluded that, "The daily cycle of temperature change, largely eliminated from modern sleep environments, may be a potent natural regulator of sleep." 

Thinking about ways to use this knowledge to help people with sleep problems, they commented: "Mimicking aspects of the natural environment might be effective in treating certain modern sleep disorders." 

Conclusion

This study of sleep patterns in non-industrialised communities indicates that sleep patterns in these communities might be more closely linked to environmental temperature and less linked to light, as had been assumed.

The use of objective sources of sleep, light and temperature information gives the study more reliability. However, the relatively short time period over which temperatures were measured – just four days – may not have given an entirely accurate picture.

Similarly, just three communities were studied – we can't assume this is representative of most non-industrialised communities. Also, the study does not take into account social and cultural attitudes to sleep, which could be a significant influencing factor. 

The study notes light has been shown to be a major factor in human sleep. In this study, sleep occurred almost entirely during the dark period. This, the researchers say, contrasts with industrial populations, where sleep typically continues well after sunrise.

It is relatively common for people to have a dip in levels of alertness mid-afternoon, with some research suggesting this is unrelated to food intake.

As a result, the authors said they expected to see napping in this afternoon dip period as a natural remedy, a bit like a siesta – but they observed no such activity. This highlights how light and temperature don't predict all sleep patterns, so there must be additional explanations – possibly social – for these activities.

Often, what you do during the day can have a big influence on how well you sleep at night. Making sure you get plenty of exercise and minimising your consumption of caffeine and alcohol should help.

Read more advice on how to get a good night's sleep.

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Is Ebola an STI? Virus can survive in semen for up to nine months

Thursday October 15 2015

The latest Ebola outbreak resulted in around 27,000 cases

"Survivors of Ebola can carry the virus in their sperm and transmit it sexually for up to nine months, a study has found," The Guardian reports.

It was previously thought the Ebola virus stayed in bodily fluids for just three months after the illness.

An obvious concern is that sexual spread of the virus could trigger another outbreak, such as the previous 2014/15 outbreak that killed thousands of people in Sierra Leone, Liberia and Guinea, leaving more than 16,000 survivors. 

The researchers found traces of Ebola virus RNA in semen samples from a group of Ebola survivors from Sierra Leone, who had been sick between two and 10 months earlier. 

The researchers say they don't know whether the traces of viral RNA detected in the men's semen came from intact viruses that could replicate and pass on the infection. They may be from fragments of virus that are no longer active.

However, a second study in the same journal found that a Liberian woman was very likely to have been infected by the Ebola virus through sex with an Ebola survivor, about six months after he was infected.

Together, the studies demonstrate that the possibility of further outbreaks of Ebola, caused by sexual transmission of the virus, cannot be dismissed.

These results, tentative as they are, do stress the usefulness of the simple, but effective, condom in helping to prevent the spread of a range of diseases.

Where did the story come from?

The first study was carried out by researchers from the Sierra Leone Ministry of Health and Sanitation; Sierra Leone Armed Forces; Sierra Leone Ministry of Social Welfare, Gender and Children’s Affairs; the Centers for Disease Control and Prevention (CDC); the World Health Organization (WHO); and the Karolinska Institute. 

It was funded by the WHO, CDC, Sierra Leone government and a Joint United Nations Program on HIV/AIDs. 

The second study was done by researchers from the US Army Medical Research Institute of Infectious Diseases; US National Institutes of Health; Liberian Ministry of Health and Social Welfare; Liberian Institute for Biomedical Research; CDC; WHO; Illumina; Naval Medical Research Unit; and the Foundation Merieux. 

It was funded by the Defense Threat Reduction Agency; Global Biosurveillance Technology Initiative; Global Emerging Infections Surveillance; Illumina; and the National Institutes for Health.

Both studies were published in the peer-reviewed journal The New England Journal of Medicine on an open-access basis, so they can be read for free online. The first is on the persistence of Ebola RNA in semen and the second is a case report showing that the virus can be spread through sexual intercourse.

BBC News and The Guardian both covered the story, in the most part, accurately. However, The Guardian reported that "survivors carry virus in their sperm", although the virus RNA is actually found in semen – the fluid that sperm live in – rather than in the sperm themselves.

What kind of research was this?

The first study was a cross-sectional cohort study using a convenience sample of volunteers. This type of study can only give us limited information, because we don't know what happens to the people in the study over time, or whether the volunteers represent the wider population.

The second study is a case report on an investigation of possible sexual transmission of Ebola virus between two people, using genomic analysis (a type of DNA analysis).

What did the research involve?

In the first study, researchers recruited 100 men who had been certified as having recovered from Ebola (which would include negative blood tests for Ebola). Each man filled out a questionnaire about his illness, and was asked to give at least one sample of semen. 

The researchers looked to see how long ago the men had been sick, when they recovered, and whether they had traces of Ebola RNA in their semen.

The tests look for evidence of genetic sequences found in the Ebola virus. However, the tests cannot tell whether these sequences are from whole, live virus, which might be infectious, or from broken-down fragments of virus, which might be harmless. Also, because the study is a snapshot in time, it cannot tell us how long signs of Ebola virus might persist in the semen. 

The study is ongoing, so longer-term data will be published in due course. The researchers also did an analysis to see how much virus there was likely to be in the semen – known as the viral load.

The second study analysed the Ebola virus RNA found in samples of blood from a woman who had died of Ebola, and blood and semen samples from her partner, an Ebola survivor, to see how likely it was that the woman had been infected by the man during unprotected sex. 

The researchers compared their results with samples from other parts of Liberia, and other contacts of the pair, to see if it was likely the woman could have been infected by another route.

What were the basic results?

The researchers had usable semen samples from 93 men in the first study. In total, half showed positive results for Ebola RNA. The samples taken from nine men who had been ill recently (within two to three months) all tested positive.

For those who had been ill four to six months earlier, 26 out of 40 (65%) were positive. For those who had been ill seven to nine months earlier, 11 out of 43 (26%) were positive, and the one man who had been ill 10 months earlier had inconclusive results. The tests for estimating viral load suggested that this became lower over time.

The results from the second study showed that the RNA of the Ebola virus found in samples from the man and woman were very similar, and much more similar than the RNA found in samples from other survivors in Liberia.

How did the researchers interpret the results?

The researchers were cautious about their results. Of the first study, they said: "the public health implications are still uncertain", because they cannot be sure whether the Ebola RNA detected in the semen was actually infectious.

However, they say they have demonstrated "the potential for transmission … even months after the outbreak has ended". They call for programmes to test and counsel survivors of Ebola about their individual risk and the best ways to avoid infecting partners.

In the second study, the researchers say "at least one case of Ebola virus disease in the ongoing Liberian outbreak probably resulted from sexual transmission through unprotected vaginal intercourse". 

Conclusion

Taken together, these studies suggest that traces of Ebola virus may remain in bodily fluids of survivors many months after people have recovered. In some cases, these traces may lead to the infection being passed on, as in the case of the Liberian man and woman in the second study. However, we don't know whether that is possible for all, or even most, people who have survived Ebola.

There have been few reports of Ebola virus being passed on through sexual contact. Given the large numbers of people who have had Ebola, and the small number of cases in recent months, it may be that Ebola is not easily transmissible by this route. 

However, there is not enough information available to speculate about this. We need much more data to know how long the virus can persist in bodily fluids, and whether it remains infectious.

In the meantime, doctors have called for the previous advice for Ebola survivors to abstain from sex or use condoms for three months to be changed. Ideally, survivors should be tested regularly, given information about their own risk, and advised to take precautions to protect their sexual partners accordingly.

The scale of the Ebola outbreak of 2014/15 has made it more important to find out about sexual transmission, because there are so many survivors now living back in their communities. 

Previous outbreaks tended to be smaller and more isolated, meaning there was less chance of transmission after the initial outbreak had been controlled.

Dr Jeremy Farrar, director of the Wellcome Trust, said the studies showed "the Ebola epidemic could be far from over". 

Using a barrier method of contraception, such as a condom during sex (including anal and oral), remains the most effective method of reducing your risk of contracting a sexually transmitted infection (STI). 

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Standing 'no healthier than sitting'

Tuesday October 13 2015

Simply standing still is no substitute for exercise

"Sitting down at work no worse than standing up," ITV News reports. A new study seems to contradict earlier advice – including recommendations on this website – that standing rather than sitting at work could bring health benefits and reduce the risk of early death.

The study featured more than 5,000 civil servants who provided information on their average sitting time doing different activities such as working, watching TV, or other leisure activities in the late 90s.

They were followed for 16 years to see if sitting time increased the risk of dying from any cause. The results showed no significant association between sitting time and risk of death.

However, the study sample only included white collar employees. And the majority of the participants were Londoners, who tend to walk and stand more as a result of the unique "challenges" posed by public transport in the capital. This means the results may not be applicable to other parts of the country.

These limitations aside, does this mean expensive standing work stations and desks are a waste of money? The lead author seems to think so: "The results cast doubt on the benefits of sit-stand work stations."

Ultimately, simply standing up is no substitute for the moderate to vigorous exercise regime recommended for healthy adults. It could be the case employers are better off investing in gym membership than new desks for their employees.   

Where did the story come from?

The study was carried out by researchers from the University of Exeter, University College London, and the University of Sydney (Australia).

It was funded by multiple UK organisations, such as the British Heart Foundation, Stroke Association, the National Heart and Lung Institute, and the National Institute on Aging.

The study was published in the peer-reviewed International Journal of Epidemiology on an open access basis, so it is free to read online or download as a PDF.

It was widely reported on by the UK media, accurately for the most part. The Guardian reported the story accurately and responsibly, but the Daily Mail's headline was exaggerated and misleading: "Couch potatoes rejoice! Sitting for long periods is NOT bad for your health, study claims."

This interpretation of the results of the study is incorrect and potentially dangerous. Sitting down may not be as bad for your health as previously thought, but it is still bad for your health.

The study only looked at overall mortality, not specific health outcomes. So sitting down all day may not kill you, but it could contribute towards your obesity or type 2 diabetes risk. Conversely, the benefits of an active lifestyle are well known. 

The Guardian quoted one of the authors of the study, Melvyn Hillsdon, who said: "Any stationary posture where energy expenditure is low may be detrimental to health, be it sitting or standing."

He added: "The results cast doubt on the benefits of sit-stand work stations, which employers are increasingly providing to promote healthy working environments." 

What kind of research was this?

This cohort study aimed to assess the association between sitting time and risk of dying in a large group of UK adults with a follow-up period of 16 years. 

The researchers considered four sitting indicators for their analysis:

• work sitting
• TV viewing time
• non-TV leisure time sitting
• total leisure time sitting

They say previous research suggested an association between sitting behaviours and increased risk of mortality, cardiovascular diseases and metabolic diseases. This study aimed to add to that evidence base by examining different types of sitting along with total time sitting and risk of death. 

Cohort studies of this type, which include a large population with a long follow-up period, can tell us if there is any association between an exposure and an outcome – but this cannot prove direct causality. 

What did the research involve?

This research included 5,132 individuals (3,720 men and 1,412 women) from a London employee-based longitudinal study of the British Civil Service, the Whitehall II study. These individuals were free of heart and vascular diseases at the start of the study period.

This study started in 1985 and included civil servants aged between 35 and 55 from clerical and office support, middle-ranking executive and senior administrative grades. The researchers took data from phase 5 (1997-99) of this study, when information on sitting behaviour was collected. 

At the start of the study, all the participants completed a questionnaire and underwent a clinical examination. Subsequent measurements were done either through a postal questionnaire alone or a postal questionnaire accompanied by a clinical examination.

In phase 5, participants provided information on work and leisure time sitting behaviours. They reported on average how many hours they spent sitting at work (including driving or commuting) and sitting at home (such as watching TV or sewing) by selecting from eight response categories (none, 1 hour, 2-5, 6-10, 11-20, 21-30, 31-40, 40 or more hours).

Mortality data was collected through the national mortality register by the National Health Service (NHS) Central Registry.

Researchers also collected data on various factors that might influence the results (confounders), such as:

• sociodemographic factors – age, gender, ethnicity and employment grade
• health-related factors – smoking status, alcohol consumption, diet quality, BMI, physical functioning and physical activity 

What were the basic results?

Over 16 years, 450 deaths were recorded among the 5,132 participants. Overall, the study found no statistically significant links between any of the five sitting indicators and risk of death.

In analyses adjusted for age, gender, employment grade and ethnicity, there was no difference in mortality risk for:

• individuals with 0-8 hours of work sitting time compared with those with more than 40 hours of work sitting a week (hazard ratio [HR] 0.81, confidence interval [CI] 0.57 to 1.14)
• individuals with 0-8 hours of TV time compared with those with more than 16 hours of TV sitting time a week (HR 1.30, CI 0.88 to 1.13)
• individuals with 0-4 hours of non-TV leisure time compared with those with more than 16 hours of non-TV leisure sitting time a week (HR 0.92, CI 0.66 to 1.28)
• individuals with 0-15 hours of leisure time compared with those with more than 26 hours of leisure sitting time a week (HR 1.36, CI 1.05 to 1.75)
• individuals with 0-26 hours of total time sitting compared with those with more than 55 hours of total sitting time a week (HR 0.95, CI 0.72 to1.27) 

How did the researchers interpret the results?

The researchers concluded by saying: "It is possible that previously reported relationships between sitting time and health outcomes are due to low daily energy expenditure, the best solution to which is to increase daily physical activity even at light intensities."

They added: "Until more robust epidemiological and mechanistic evidence exists about the risks of prolonged sitting, the promotion of a physically active lifestyle should still be a priority." 

Conclusion

This cohort study aimed to assess the association between sitting time and overall risk of death in a large sample of UK civil servants with a follow-up period of 16 years.

The results showed no association between sitting time and risk of death. The results of this study have relevance for policy makers and employers to promote recommended daily physical activity.

While this study reports some interesting findings, the results should be interpreted with some caution because of the study's limitations. The study does have strengths in its large sample size, long duration of follow-up period, and examination of mortality outcomes through a national register.

However, as acknowledged by the researchers, this Whitehall study only included white collar employees, mainly based in London, so the results cannot be generalised to all populations. 

It is also possible people may not be able to give reliable estimates of their sitting time, and these one-off measures taken at the end of the 90s are not representative of lifelong sedentary and activity patterns.

And although the researchers adjusted for some confounding factors, there may be various other health and lifestyle factors that are not considered in the analysis that might have had an influence on the results.

But the findings do not suggest you can regularly sit for long periods and get no exercise but still maintain good health. Sitting down on a regular basis may not directly increase your risk of death, but it could contribute towards the risk of developing chronic diseases such as type 2 diabetes and obesity, which can have an adverse impact on your quality of life.

The importance of healthy eating and daily physical exercise to maintain good health are well recognised. Current physical activity recommendations for adults are 150 minutes of moderate aerobic activity a week, accompanied by strength exercises on two or more days of the week. 

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