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Can exercise offset some of the harms of regular drinking?

NHS Choices - Behind the Headlines -

"Adults who booze regularly but exercise for five hours a week are no more likely to die than teetotallers," the Mail Online reports.

A study suggests exercise may compensate for some, but certainly not all, of the harms associated with excessive alcohol consumption. This latest study looked at deaths from cancer and cardiovascular disease, as well as premature death in general (usually judged to be dying before the age of 75).

Researchers looked at around 10 years' worth of national survey data from UK adults aged over 40. Unsurprisingly, they found links between all-cause and cancer mortality in inactive people. But they also found increasing levels of physical activity generally removed the association with drinking habits. In fact, occasional drinking was associated with a significant reduction in all-cause mortality for the most active of people.

Although the study had strengths in its large sample size and regular follow-up, we can't be sure that any links observed were solely down to the interaction between alcohol and exercise. For example, people who are physically active may also avoid smoking and consume healthy diets. It is difficult to completely control for such influences when analysing data like this.

While regular exercise may mitigate against some of the harms associated with excessive alcohol consumption it certainly won't make you immune. Many world-class sportspeople, such as George Best and Paul Gascoigne, have had both their careers and lives blighted by drinking.

 

Where did the story come from?

The UK-based study was carried out by an international collaboration of researchers from Canada, Australia, Norway and the UK. The health surveys on which the study was based were commissioned by the Department of Health, UK. Individual study authors also reported receiving funding from the National Health and Medical Research Council and University of Sydney. 

The study was published in the peer-reviewed British Journal of Sports Medicine. 

The media coverage around this topic was generally overly optimistic, highlighting that by exercising, individuals can completely undo the harm caused by excessive alcohol consumption, which is untrue.

In particular, the Mail Online claimed "Adults who booze regularly but exercise for five hours a week are no more likely to die than teetotallers" which could send out the wrong message to the public.

 

What kind of research was this?

This cohort study analysed data from British population-based surveys: Health Survey for England (HSE) and the Scottish Health Survey (SHS) to investigate whether physical activity is able to moderate the risk between alcohol consumption and mortality from cancer and cardiovascular diseases.

Cohort studies like this are useful for assessing suspected links between an exposure and outcome. However, there are potentially other factors that have a role to play in such associations and therefore the study design doesn't allow for confirmation of cause and effect.

 

What did the research involve?

The researchers collected data on 36,370 men and women aged 40 or above from Health Survey for England (1994; 1998; 1999; 2003; 2004; and 2006) and the Scottish Health Survey (1998 and 2003). Among other things, the participants were asked about their current alcohol consumption and physical activity.

Alcohol intake was defined by six categories (UK units/week):

  • never drink (lifetime abstainers)
  • ex-drinkers
  • occasional drinkers (haven't drank anything in past seven days)
  • within (previous) guidelines: <14 units (women) and <21 units (men)
  • hazardous: 14-15 units (women) and 21-19 units (men)
  • harmful: >35 (women) and >49 (men)

Frequency and type of physical activity in the past four weeks was questioned and converted into metabolic equivalent task-hour (MET-hours, which are an estimate of metabolic activity) per week according to national recommendations:

  • inactive (≤7 MET-hours)
  • lower level of active (>7.5 MET-hours)
  • higher level of active (>15 MET-hours)

The surveys were linked to the NHS Central Register for mortality data and the participants were followed up until 2009 (HSE) and 2011 (SHS). There were 5,735 recorded deaths; deaths from cancer and cardiovascular disease were of most interest for this study.

The data was analysed for associations between alcohol consumption and the risk of death from all-causes, cancer and cardiovascular disease. The results were then analysed according to levels of physical activity.

Potential confounders (such as sex, body mass index and smoking status) were controlled for.

 

What were the basic results?

Overall, the study found a direct link between all levels of alcohol consumption and risk of cancer mortality. It also found that increasing levels of physical activity reduced this association with cancer mortality, and also reduced the link with death from any cause.

  • In individuals who reported inactive levels of physical activity (≤7 MET-hours), there was a direct association between alcohol consumption and all-cause mortality.
  • However, in individuals who met the highest level of physical activity recommendations a protective effect of occasional drinking on all-cause mortality was observed (hazard ratio: 0.68; 95% confidence interval (CI): 0.46 to 0.99). It should be noted that this result just skimmed the cut-off point for statistical significance.
  • In this high activity group, there was no link between all-cause mortality and alcohol consumption within guidelines, or even hazardous amounts, but the risk was still increased for those drinking harmful amounts.
  • The risk of death from cancer increased with the amount of alcohol consumed in inactive participants, ranging from a 47% increased risk for those drinking within guidelines to 87% increased risk for those with harmful drinking.
  • In people with higher activity levels (above 7.5 MET hours) there was no significant link between any amount of alcohol consumption and cancer mortality.
  • No association was found between alcohol consumption and mortality from cardiovascular disease, although a protective effect was observed in individuals who reported the lower and higher levels of physical activity (>7.5 MET-hours) and (>15 MET-hours) respectively.

 

How did the researchers interpret the results?

The researchers concluded "we found evidence of a dose–response association between alcohol intake and cancer mortality in inactive participants but not in physically active participants. [Physical activity] slightly attenuates the risk of all-cause mortality up to a hazardous level of drinking."

 

Conclusion

This study aimed to explore whether physical activity is able to moderate the risk between alcohol consumption and mortality from cancer and cardiovascular diseases. It found that increasing levels of physical activity reduced the association for death from both all-causes and cancer.

This study has strengths in its large sample size, comprehensive assessments and long duration of follow-up. The findings are interesting, but there a few points to bear in mind:

  • As the authors mention, cohort studies such as this are unable to confirm cause and effect. Though the researchers have tried to account for various potential health and lifestyle confounding variables, there is the possibility that others are still influencing the results. A notable one is dietary habits which weren't assessed. Also, for example, the former drinkers may have quit due to other health issues which may have introduced bias.
  • The study was unable to look at binge drinking levels of alcohol consumption which would have likely had important health implications.
  • Additionally, there is always the possibility with self-reported surveys that the participants either under or over-reported their drinking habits which can increase the chance of misclassification bias.
  • Though having a large sample size, fewer people reported harmful drinking levels, so links within this category may be less reliable.
  • The study has only looked at the link between alcohol and actually dying from cancer or cardiovascular disease. Links may be different if they looked at associations between alcohol and just being diagnosed with cancer or heart disease, for example.
  • The study is also only representative of adults over the age of 40.

Overall, maintaining a healthy lifestyle seems to be the best bet for reducing the risk of any chronic disease, be it through physical activity, balanced diet or reasonable alcohol consumption.

Current alcohol recommendations for both men and women are to drink no more than 14 units per week.  

Links To The Headlines

How exercise undoes the harm from drinking: Adults who booze regularly but exercise for five hours a week are no more likely to die than teetotallers. Mail Online, September 8 2016

Two hours a week of exercise could offset the dangers of alcohol. The Daily Telegraph, September 8 2016

Exercise can cut risk from alcohol-related diseases, study suggests. The Guardian, September 8 2016

Links To Science

Perreault K, Bauman A, Johnson N, et al. Does physical activity moderate the association between alcohol drinking and all-cause, cancer and cardiovascular diseases mortality? A pooled analysis of eight British population cohorts. British Journal of Sports Medicine. Published online August 31 2016

Fitness trackers' calorie measurements are prone to error

NHS Choices - Behind the Headlines -

"Fitness trackers out of step when measuring calories, research shows," The Guardian reports. An independent analysis of a number of leading brands found they were all prone to inaccurate recording of energy expenditure.

Researchers recruited 60 participants to take part in a range of exercises while having their heart rate and number of calories burned measured by fitness trackers, as well as by clinically-approved medical devices used in a clinical setting. Seven fitness trackers were tested, including the Apple Watch, Fitbit Surge and the Samsung Gear S2.

The data from the fitness trackers was compared against the data obtained by the clinically-approved devices to calculate any errors in the measurements.

The researchers found that although fitness trackers are generally reliable in their ability to measure heart rate, they perform poorly when measuring the number of calories burned. The results showed that, out of all seven devices, the Apple Watch had the lowest error in measurements whereas the Samsung Gear S2 had the highest level of error in terms of heart rate measurement and the PulseOn in terms of calorie burning measurement.

For now, fitness trackers remain useful for individuals to have an idea of how many calories they may have burned over a day but it should be kept in mind that these devices are not always 100% accurate, as shown by this study.

And if you are trying to lose weight, focusing on an overall weekly goal for exercise and activity may be a better approach than trying to measure every single calorie burning exercise from one day to the next.

Read more advice about meeting your weight-loss goals.

 

Where did the story come from?

The study was carried out by researchers from Stanford University in the US and the Swedish School of Sport and Health Sciences in Stockholm. No external sources of funding were reported.

The study was published in the peer-reviewed Journal of Personalized Medicine. The article is available on an open access basis, which means it's free to read online.

UK media coverage on this topic was generally accurate.

 

What kind of research was this?

This was an experimental study that assessed how accurately seven fitness trackers are able to measure heart rate and calories burned compared to a "gold standard" assessment of heart rate and energy expended in an exercise laboratory.

Commercially available fitness trackers are increasingly being used by individuals as part of fitness monitoring or weight loss programmes. The results from the devices are often compared to average population levels and in theory could inform decisions made by doctors. Prior to this study the accuracy of the data produced by consumer trackers hasn't been evaluated in great detail.

This type of study is a useful way to compare the different trackers against a "gold standard" measurement and will help individuals decide how much trust they can have in their devices.

 

What did the research involve?

The researchers chose fitness trackers which:

  • are worn on the wrist
  • continuously measure heart rate
  • have a battery life of more than 24 hours
  • were available to consumers at the time of the study

Seven fitness trackers were evaluated:

  • Apple Watch
  • Basis Peak
  • Fitbit Surge
  • Microsoft Band
  • Mio Alpha 2
  • PulseOn
  • Samsung Gear S2

60 participants (29 men and 31 women) over the age of 18 were recruited to take part in the assessment. Participants were selected to represent a diverse range of age, height, weight, skin tone and fitness level.

The individuals wore the fitness trackers while sitting, walking, running and cycling. They were simultaneously monitored using clinically approved instruments: electrocardiograms (ECG) and continuous clinical grade indirect calorimetry.

Indirect calorimetry is a laboratory technique for measuring fitness in which the maximum oxygen intake while breathing on the treadmill or bicycle ergometer is measured and a standard formula is used to estimate energy expended. It was used here as a gold standard for measuring calories burned.

The data from the fitness trackers was analysed against data from these clinically approved instruments. Heart rate from the fitness trackers was compared with data obtained from the ECG and the number of calories burned was compared with the data from the indirect calorimetry. The percent of error in relation to the clinical devices was then calculated.

 

What were the basic results?

Overall, the researchers found that most fitness trackers were able to measure heart rate fairly accurately, but poorly estimated the number of calories burned.

Of the seven fitness trackers, the Apple Watch performed best whilst the Samsung Gear S2 had the largest errors when measuring heart rate and calories burned.

Heart rate:

  • The Apple Watch achieved the lowest error when measuring heart rate: 2.0% (1.2%-2.8%).
  • Samsung Gear S2 had the highest error: 6.8% (4.6%-9.0%).

Calories burned:

  • The Fitbit Surge performed best with the lowest error of all seven trackers: 27.4% (24.0%-30.8%).
  • PulseOn had the highest error: 92.6% (87.5%-97.7%).

 

How did the researchers interpret the results?

The researchers concluded: "We assessed, in a controlled laboratory setting, the reliability of seven wrist-worn devices in a diverse group of individuals performing walking, running and cycling at low and high intensity. We found that in most settings, heart rate measurements were within acceptable error range (5%). In contrast, none of the devices provided estimates of energy expenditure that were within an acceptable range in any setting.

"Individuals and practitioners should be aware of the strengths and limitations of consumer devices that measure heart rate and estimate energy expenditure."

 

Conclusion

This study assessed how accurately seven fitness trackers are able to measure the heart rate and calories burned of individuals taking part in several different activities. The data was compared against clinically approved medical devices to test the accuracy of data obtained by the fitness trackers.

It found that although all seven trackers were fairly accurate at measuring heart rate, there was a high level of error when measuring the number of calories burned.

The researchers hope this study will help individuals and physicians be aware of potential errors when interpreting the measurements obtained by fitness trackers, especially when using the data to inform treatment options in a clinical setting.

This is an interesting study but it is small and would require further testing of devices with a larger number of participants to verify the findings. For now, fitness trackers remain useful if you want to compare data on yourself over time, but they shouldn't be relied upon if you're trying to replace calories burned with a "treat".

If your goal is to lose weight through exercise, then bear in mind it's very much a "marathon not a sprint". Increasing your activity and exercise levels on a long-term basis is more important than obsessing about exactly how many calories you may have burned during a single run or gym session.

The NHS weight loss plan is designed to help you lose weight, through a combination of diet and exercise, over the course of 12 weeks.  

Links To The Headlines

Fitness trackers out of step when measuring calories, research shows. The Guardian, May 24 2017

Fitness trackers 'poor at measuring calories burned'. BBC News, May 25 2017

Fitness trackers may be incorrectly counting calories burnt, finds research. The Independent, May 25 2017

Links To Science

Shcherbina A, Mattsson CM, Waggott D, et al. Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort. Journal of Personalised Medicine. Published online May 24 2017 

Does meditation carry a risk of harmful side effects?

NHS Choices - Behind the Headlines -

"Meditation can leave you feeling even more stressed," the Daily Mail reports.

The claim is prompted by a study of 60 practitioners of Buddhist meditation in the US which found they'd had a range of "challenging or difficult" experiences associated with the practice.

However, it's not clear how relevant the results are to the majority of people who use meditation apps or take mindfulness classes.

The study only included people in Western countries who meditated within one of three Buddhist traditions, and – importantly – who'd had negative experiences. So the numbers of people in the study reporting, for example, fear, is only representative of people who'd said they had a negative experience through meditation, not of all people meditating.

The study does make an important point, however, at a time when mindfulness and meditation has become more popular, that the effects of meditation are not always positive or harmless. Some people in the study reported feeling depressed or suicidal, and a few needed treatment in hospital as a result.

Classical Buddhist literature discusses potential pitfalls of mindfulness and meditation, such as makyō (hallucinations) and "Zen sickness" – a sense of imbalance and loss of identity. So these warnings should not be glossed over by teachers of Buddhist inspired techniques.

Also, healthcare practitioners who recommend meditation need to be aware of the associated risks. 

 

Where did the story come from?

The study was carried out by researchers from Brown University and the University of California in the US. It was funded by the National Center for Complementary and Integrative Health, the Bial Foundation, the Mind and Life Institute and the 1440 Foundation.

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

The Mail covered the study particularly badly. It began by sneering at the celebrities and "yummy mummies" that practice mindfulness, without apparently noticing that the study excluded generic mindfulness-based interventions and looked only at specific Buddhist meditation practices.

It reported that 82% of people questioned had experienced fear, anxiety or paranoia, without making it clear the study only interviewed people with negative experiences. It also said that people who had previous psychological problems had been "ruled out" of the study. Yet the study reported 32% of people interviewed had a history of psychiatric disorder (only people with current mental illness, or similar unusual psychological experiences not linked to meditation were excluded).

Finally, the Mail said the study interviewed "nearly 100" people about their experiences, when they actually interviewed 60 people.

 

What kind of research was this?

This was a qualitative study. Qualitative studies, like this one, use interviews to ask people open-ended questions about their experiences of specific issues, such as meditation.

Experiences were then grouped into categories. The researchers looked specifically for people who'd had negative experiences of meditation, because they say these experiences had not previously been properly investigated.

This type of research is useful to gather detailed information about people's experiences. It doesn't tell us how common these experiences are, what causes them, or why these people in particular experienced them.

 

What did the research involve?

Researchers recruited 60 people who were regular practitioners of one of three types of Buddhist meditation, and who had experienced a challenging or negative experience linked to meditation.

They interviewed them about what they experienced, how they understood it, and what effect it had. They also interviewed 30 "experts" – mostly meditation teachers – about their understanding of what caused challenging experiences and how they could be managed.

The interviews were used to compile models of types of experience (described as "domains") and models of the factors that could affect people's likelihood of having this type of experience. Researchers say this element should only be understood as the opinions (often conflicting) of the teachers and experts interviewed, not as a definitive list of causes.

 

What were the basic results?

Researchers identified eight "domains" of experience from the interviews, which included both positive and negative experiences. These were:

  • Cognitive, or related to thinking. This included changes in world view, delusions, irrational or paranormal beliefs, mental stillness, and change in the way people made decisions to do things (executive function).
  • Perceptual, or related to information from the senses. This included hallucinations, visions or illusions, seeing lights and being more sensitive to sensory stimuli such as noise or bright light.
  • Affective, or related to emotions. This included fear, anxiety, panic or paranoia, which were the most commonly reported group of challenging experiences; feeling blissful or very happy; depression or grief; re-experiencing of traumatic memories.
  • Somatic, or related to body. This included feeling bursts of energy, changes to sleep patterns, feelings of pain, and both increased or released pressure or tension.
  • Conative, or relating to motivation. This included changes in motivation, change in effort, loss of enjoyment of things usually found enjoyable and loss of interest in doing things.
  • Sense of self, which included feeling a loss of boundaries between self and the rest of the world, a loss of sense of self.
  • Social, which included difficulties in interacting with people, especially after returning from a meditation retreat or period of intensive practice.

Of the practitioners interviewed, 60% were also meditation teachers, and 41% of them said their challenging experiences followed meditation of 10 hours a day or more. This suggests they were more intensive practitioners than the average person doing perhaps half an hour a day.

The researchers said the experiences were likely to be caused by meditation, as they'd passed criteria designed to assess causation. These included whether they happened at the time of the meditation practice, whether they were linked to more intense practice, whether they receded when people stopped meditating and returned when they began again, and that they were consistently reported by people in the study.

Some experiences were directly caused by meditation, while others might be secondary – for example, fear at loss of sense of self – or even tertiary – for example distress at the way they were treated by a meditation teacher after having a challenging experience.

 

How did the researchers interpret the results?

The researchers say the results suggest that "meditation practices – on their own – may produce challenging effects, but the specific type of effect, as well as its likelihood, duration, and associated distress and impairment, is influenced by a number of additional factors."

They add that the results "should not be interpreted as conclusive" because the study is one of the first in its field.

 

Conclusion

Many people around the world find meditation can be helpful. However, as with most things, there can be downsides.

Some people – especially if they practice intensive meditation for many hours, such as on a retreat – have challenging or difficult experiences. Some religious teachers within Buddhism say these can be part of the path of the religious experience. However, for people doing meditation hoping to experience health benefits, without a religious context, these experiences can be unexpected and difficult to deal with.

There are limitations in this study that mean we shouldn't try to apply it too widely. The people interviewed were quite a select group – all had volunteered to talk about challenging experiences during meditation, the majority were meditation teachers, they were almost all white and highly educated (42% had a master's degree and 25% a doctorate). Their experiences may be different from those of the average person attending a meditation class or using a meditation or mindfulness app on their phone.

The serious, long-lasting nature of some of the negative experiences reported, however, are cause for concern. People who experience depressionsuicidal feelings or other serious problems after meditation should seek medical help.

Links To The Headlines

The dangers of meditation: It can actually lead to insomnia, fear and hypersensitivity to light. Daily Mail, May 25 2017

Links To Science

Lindahl JR, Fisher NE, Cooper DJ, et al. The varieties of contemplative experience: A mixed-methods study of meditation-related challenges in Western Buddhists. PLOS One. Published online May 24 2017

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