November 29, 2016

expert reaction to study reporting associations between different types of sports and mortality

Publishing in the British Journal of Sports Medicine, researchers looked at the associations of six different types of sport with cardiovascular disease mortality risk. They reported that specific types of sport are associated with differing risk levels.

Dr Mike Knapton, Associate Medical Director, British Heart Foundation, said:

“This is a large cohort study of participants in the Health Survey for England and the Scottish Health Survey and can be viewed as robust. The data supported the conclusions made by the authors, as participation in certain types of sport and exercise showed a substantial reductions in all-cause and CVD mortality for swimming, racquet sports and aerobics and in all-cause mortality (only) for cycling.  An unexpected finding was the lack of an association between sport related exercise from running and football and all-cause mortality and CVD mortality. It is not clear what mechanism might be behind these unexpected associations. There is a paucity of data on the association between participation in sport and health outcomes and this study adds to the current evidence base.

“However one limitation of this study is that it only reports observed associations between sport and all cause/CVD mortality.  The participation in sport was self-reported which may be inaccurately recalled and reported and could include over- or under-reporting.  Some sports are seasonal and this might explain some of the observations e.g. timing of the survey and the football season.  There were also relatively few deaths in some subgroups (e.g. football) which could mean the numbers were too underpowered to see a change in all cause/CVD mortality.

“Give the limitations of the study set out above I think it is fair to say this study suggests participation in  sport is associated with an improvement in all cause and CVD mortality – but this was only observed in particular sports such as swimming, racquet sports, aerobics and cycling (all-cause mortality only).

“This study alone does not change the current UK CMO guidelines on physical activity (2011).  However, it does give confidence that participation in some sports is associated with substantial reduction in all cause and CVD mortality.  This association is similar to the association between generic forms of physical activity (e.g. walking). For most people the motivation to engage in sport related physical activity is, and should remain, enjoyment of the sport, and team camaraderie that is linked to team games.  If you enjoy running or football, do not let these finding put you off!

“Those who are not keen on participation in  sport can be reassured that they can maintain their health and fitness in other ways including being active daily and over a week aim for 150 minutes of moderate intensity activity, such as walking or cycling and reducing the amount of time they spend in sedentary activity. Despite only certain types of exercise showing a reduced risk of developing heart and circulatory disease in this study, doing 150 minutes of moderate intensity activity a week is still the recommended guidelines. The majority of people are not reaching this target and I would encourage people to take part in a form of exercise that they enjoy and motivates them help them achieve this.”

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

“This study must not be misinterpreted as showing that running and football do not protect against heart disease. In this study both runners and footballers had a lower rate of death from heart disease. Although this was not “statistically significant”, many other studies have found that runners live longer and suffer less heart disease. This study relied on a single questionnaire to determine what amount and type of physical activity people were engaged in, and although this is a standard approach to obtain information from many thousands of people (in whom it is impractical to measure activity more accurately) this is unreliable. Studies that actually measure the amount of activity being performed usually show even greater benefits of exercise because they weed out people who overestimate or exaggerate how active they are. I suspect the rise of smartphones and activity trackers will provide more convincing evidence of the benefits of activity on the risk of heart disease. In the meantime, I will continue to tell my patients that regular physical activity (including running) is more effective in reducing their risk of heart disease than any drug I can prescribe.”

Prof Sir David Spiegelhalter, Winton Professor for the Public Understanding of Risk, University of Cambridge, said:

“The authors’ distinction between cycling and swimming as having ‘significant’ associations with all-cause mortality, from running and football which do not, is simply not valid. The associations for all four activities cannot be statistically differentiated from each other – it’s just that there were so few deaths among runners and football players.

“Also, although activity may well reduce the risk of death in the long-term, it is equally plausible that the ‘causation’ may go the other way in the short-term – those at increased risk death over the next few years are less likely to be healthy enough to play active sports now.”

* ‘Associations of specific types of sports and exercise with all-cause and cardiovascular-disease mortality: a cohort study of 80 306 British adults’ by Oja et al. was published in British Journal of Sports Medicine on Tuesday 29th November.

Declared interests

Dr Mike Knapton: No conflicts of interest.

Dr Tim Chico: “I am a committee member and Treasurer of the British Atherosclerosis Society, a charity established in 1999 to promote UK atherosclerosis research.”

Prof Sir David Spiegelhalter: No conflicts of interest.