September 21, 2017

expert reaction to study looking at physical activity and prevention of cardiovascular disease and early death

A new study, published in the Lancet, examines the association between higher recreational and non-recreational physical activity and lower risk of mortality and cardiovascular disease.

Dr David Nunan, Senior Researcher at the Centre for Evidence Based Medicine, University of Oxford, said:

“This study is a follow-on from the recent Lancet study assessing the association between diet and health, only this time it looks at the relationship with self-reported physical activity and health outcomes predominantly in low- and middle-income countries (83%).  It found beneficial dose-dependent associations of all forms of physical activity with reduced mortality and cardiovascular disease risks and confirms similar associations observed in high-income countries.  The basic message being if you move around more you’re less likely to die early or suffer a cardiovascular event.

“Like the previous study there are many strengths, not least the large number of participants (130,843) and the attempts made to standardise the way information about physical activity levels and outcomes were obtained across and within countries.

“However, the study suffers from limitations inherent with observational study designs, that being systematic differences between groups for important characteristics that were and were not measured.  This is perhaps reflected by some noticeable differences between groups in some characteristics.  It is quite possible that the higher mortality observed in this study in groups who are less physically active reflects differences in socio-economic status that cannot be adequately removed from the statistical analysis of the relationship between physical activity and health outcomes.

“A key issue, which the authors acknowledge, is reverse causality, whereby any observed effect is being driven by the fact that people who become ill stop being as physically active as they may have been at the start of the study.  Whilst some attempts to control for this were made, it cannot be completely ruled out.

“Interestingly, 82% of the participants reported that they were meeting recommended levels of 150 minutes physical activity a week.  However, this was predominantly due to non-recreational activities and reflects the differences between low/middle-income and high-income countries.  In addition, only 11% of participants are from Europe or North America and the relevance of this data for UK populations may be limited.

“The authors report the relative risk associated with being more physically active but it is also important to consider the absolute risk for the individual. The risk of early death plus major cardiovascular disease in people who did not meet recommended physical activity levels was 8.2%.  The risk in people who did meet recommended physical activity levels was 5.9%, a difference of 2.3%.  This means for every thousand people who meet the recommended physical activity levels, 23 will be spared an early death or a cardiovascular event.

“None the less, the importance of increasing physical activity levels at the population level should continue to be stressed, particularly given the additional multitude of associated benefits of a more physically active society as highlighted in the accompanying editorial.”

Dr Tim Chico, Reader in Cardiovascular Medicine / consultant cardiologist, University of Sheffield, said:

“This well-conducted study observed a huge number of people, and confirms that physical activity is associated with reduced risk of heart disease or dying irrespective of whether or not someone lives in a low-, middle- or high-income society.  The protective effects of exercise were greatest in high-income countries like the UK; a high level of activity almost halved the risk of heart disease or dying.

“The large number of people studied means that the findings are reliable, and its findings are similar to many previous smaller studies that found people who exercise have a lower risk of heart disease.

“There has been speculation that higher levels of activity may not be any better than moderate exercise, or even possibly harmful, but this study clearly shows that the more exercise someone does, the lower their risk of heart disease.  However, people should not be daunted, since 30 minutes five times a week gave almost as much benefit as much higher levels of activity.

“We no longer need more evidence to confirm the benefit of exercise in reducing heart disease; it does this more powerfully than any drug available.  What we need is to understand why so many people do so little exercise, and what can be done to make regular physical activity a part of everyone’s daily routine.”

Dr Rhys Thatcher, Reader at Aberystwyth University, Fellow of the British Association of Sport and Exercise Sciences, BASES accredited Sport and Exercise Scientist, and Vice Chair of Research and Development for the Hywel Dda Local Health Board, said:

“Since the early work of Ralph Paffenbarger and Steven Blair in the United States and Jerry Morris in the UK, who followed cohorts of individuals in the 1960s, the link between physical activity and reduced rates of death (all-cause mortality) has been well known.  The reduced death rates were attributed to reductions in cardiovascular disease brought about by the increase in physical activity.

“These early studies informed the current physical activity guidelines of 5 x 30 (30 minutes, five time a week).

“The latest study reported in the Lancet, confirms these findings and highlights that the issue of low levels of physical activity is not just a western issue – where the vast majority of the previous research in this area had been done – but is a major global issue.  It is the first study to report on such a large cohort across 17 different countries reflecting a range of cultures and economic status.

“This study also highlights three key issues.

“Firstly, that there is no cap on the benefits of activity i.e. there is a clear dose- response relationship – the more you do the more benefit you get.

“Secondly, the importance of transport and daily activity in work and the home rather than structured, planned exercise, as the majority of people who achieved high physical activity did so via these activities.

“Finally, the impact on the health of people across the globe of increasing physical activity is unparalleled by any other intervention.”

Prof. Metin Avkiran, Associate Medical Director, British Heart Foundation (BHF), said:

“We already know from previous research that physical inactivity increases people’s risk of heart disease and directly contributes to one in six deaths.

“This study adds to that evidence, and also indicates that the benefits of regular exercise in lowering heart disease risk and prolonging life apply across countries with very different socioeconomic circumstances.

“In an age where we’re living increasingly busy but often sedentary lives in the west, weaving physical activity into our daily routines has never been more important, not only to improve our physical health but also overall well-being.  Increased physical activity could have an even greater beneficial impact in lower income countries, due to its low its cost and the high incidence of heart disease in those countries.

Are the conclusions backed up by solid data?

“Yes, this is a significantly large study on a global scale.

Have the authors accounted for confounders?  Are there important limitations to be aware of?

“They have accounted for confounders as much as possible, but a limitation is that this is an observational study that relies on self-reported activity data.”

Prof. John Martin, Professor of Cardiovascular Medicine, UCL, said:

“This is an important study as it extends our knowledge of an important beneficial effect of walking to populations with middle and low income.  A strength of the article is the large number of subjects involved.  A weakness as the authors admit is the definition of high and low income communities across many countries.  A strength is that the finding is compatible with other studies of exercise and prevention of cardiovascular disease.  Also we know much about the biological benefit of exercise, particularly the effect on the production of beneficial factors from the lining of arteries (the endothelium).  So it fits well with our previous knowledge.

“There is a trend for more heart disease in lower income groups both within and between populations.  In the UK it has been shown that lower social class is associated with more heart disease.  Walking is easy and cheap.  This study should encourage governments to rebalance health budgets away from high tech treatment of heart disease to promoting simple strategies of prevention like walking.”

Dr James Rudd, HEFCE Senior Lecturer in Cardiovascular Medicine, University of Cambridge, said:

“This large, well conducted study estimated levels of physical activity in people from low, middle and high-income countries across the world using a questionnaire.  The clear-cut results reinforce the message that exercise truly is the best medicine at our disposal for reducing the odds of an early death.  If a drug company came up with a medicine as effective as exercise, they would have a billion-dollar blockbuster on their hands and a Nobel prize in the post.”

* ‘The effect of physical activity on mortality and cardiovascular disease in 130 000 people from 17 high-income, middle-income, and low-income countries: the PURE study’ by Scott A Lear et al. published in The Lancet on Thursday 21 September 2017.

Declared interests

Dr David Nunan: “None.”

Dr Tim Chico: “No conflicts.”

Dr Rhys Thatcher: “I have no conflict of interest (other than spending the last 20 years trying to get people to exercise more).  I do not know or have had any contact with the authors of the paper or their funders.”

Prof. John Martin: “I have no conflict of interest.”

Dr James Rudd: “No conflicts of any sort.”