This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
People who are more physically active in middle age are less likely to die early, whether they do light or moderate to vigorous activity.
The largest reductions in death are seen for those who do around 375 minutes a day of light intensity physical activity, such as walking, cooking or gardening, or 24 minutes a day of moderate to vigorous physical activity.
People who did most exercise were 73% less likely to have died early than those who did the least. Whereas, people who were sedentary for 9.5 hours or more were about twice as likely to die early, while enrolled in the studies.
Researchers reviewed data from eight studies (including 36,383 adults aged over 40) in which people wore activity monitors to record their movements. The average follow-up was 5.8 years.
The study strengthens the evidence in support of the current UK guidelines on physical activity for adults.
Why was this study needed?
The 2016 Health Survey for England (the most recent for which figures are available) showed that only 66% of men and 58% of women aged 16 and over said they met the aerobic guidelines of at least 150 minutes of moderate activity or 75 minutes of vigorous activity each week.
Sedentary lifestyles are known to contribute to a wide range of health problems including obesity, musculoskeletal problems and cardiovascular disease. Physical activity is also thought to be beneficial for mental health.
Previous reviews and many previous studies of the link between physical activity and mortality have included self-reported activity levels, which may not be accurate.
This review included only studies in which people wore accelerometers, which record physical activity, so should give a more accurate picture.
What did this study do?
The authors carried out a systematic review, which found eight eligible cohort studies (36,383 participants aged 40 or over). These only included studies with objective measurements of activity, where participants were given an actigraph unit, and from which they were able to obtain mortality data. They requested that the original study authors re-analyse their data according to a standardised protocol, mainly classifying exercise uniformly. This allowed them to reduce the variation between studies and more accurately find associations.
Adjusting for age, sex, socioeconomic status, body mass index and other available confounding factors, they calculated the association with mortality for quartiles of physical activity, from highest to lowest time spent in different intensity of physical activity. They also calculated the association between mortality and sedentary time, adjusted to take account of time spent in moderate to vigorous physical activity. Healthy people are likely to exercise more, but the researchers took steps to reduce the chances that this could explain their results.
What did it find?
- Compared with the quartile of people who did the least total physical exercise, the quartile who did the most were 66% less likely to have died (hazard ratio [HR] 0.34, 95% confidence interval [CI] 0.29 to 0.41), based on 35,932 participants.
- Small increments of additional activity were enough to produce a reduced risk of mortality. People in the second quartile (participating in about 60 minutes a day of additional light activity) had a 34% lower risk of death than those in the lowest quartile (HR 0.66, 95% CI 0.58 to 0.74).
- Compared with the quartile of people who were least sedentary, the quartile who were the most sedentary had a more than two-fold risk of having died (HR 2.18, 95% CI 1.61 to 2.95), based on 35,932 participants.
- The maximal risk reductions were for 375 minutes of light intensity physical activity (HR 0.48, 95% CI 0.38 to 0.63) and 24 minutes of moderate to vigorous intensity physical activity (HR 0.39, 95% CI 0.26 to 0.59). Above this level, there were no further risk reductions. People doing more than about 30 minutes of moderate to vigorous intensity activity a day seemed to have a slightly increased risk of mortality. However, few people did moderate to vigorous activity at this level so these figures may not be especially reliable.
What does current guidance say on this issue?
Current recommended physical activity guidance for adults in the UK is to be active every day, and to do at least 150 minutes of moderate aerobic activity each week (or 75 minutes of vigorous aerobic activity), plus strength exercises on two days or more each week.
This is similar to the moderate to vigorous physical activity definition found in the study.
What are the implications?
The review found stronger links between mortality and physical activity than have been found in previous reviews, perhaps because it had more accurate information about activity levels.
The findings confirm the important place of physical activity in a healthy lifestyle, and support the physical activity advice for adults in the UK.
Healthcare workers could stress the many advantages of physical activity, even at low intensity. Public health interventions should also aim to enable more people to be active and take up more vigorous activity.
Citation and Funding
Ekelund U, Tarp J, Steene-Johannessen J et al. Dose-response associations between accelerometry measured physical activity and sedentary time and all cause mortality: systematic review and harmonised meta-analysis. BMJ. 2019;366:l4570.
There was no specific funding for this study.
Bibliography
Department of Health and Social Care, Llwodraeth Cymru Welsh Government, Department of Health Northern Ireland and the Scottish Government. UK Chief Medical Officers' physical activity guidelines. Department of Health and Social Care, Llwodraeth Cymru Welsh Government, Department of Health Northern Ireland and the Scottish Government; 2019.
Klenk J and Kerse N. Every step you take. BMJ. 2019;366:l5051.
NHS website. Physical activity guidelines for adults aged 19 to 64. London: Department of Health and Social Care, updated October 2019.
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