Being physically active at a 'moderate' level for 75 minutes a week helps to reduce health risks
One early death in 10 could have been prevented if everyone had met just half the recommended weekly target of 150 minutes of moderate intensity physical activity, according to an article that was published online today (1 March) in the British Journal of Sports Medicine.
The article – based on largest pooled data analysis of its kind – found that exercising for just 75 minutes a week substantially reduces the risks of early death and cardiovascular disease. The risk for developing certain cancers, including those of the head and neck and myeloid leukaemia, were also affected, the analysis shows.
Higher levels of physical activity are associated with lower risks of death from all causes. But differing methods used in previous pooled data analyses on which these associations are based, make it difficult to pinpoint reduced risks for specific outcomes. And workplace physical activity, which is hard to measure, has often been included in these analyses, explain the researchers.
Research based on 'new framework'
To overcome these issues, the researchers deployed a new framework that enabled them to compare studies measuring and reporting physical activity in many different ways; to exclude resting energy expenditure; and for the first time, to explore the dose-response links between leisure time physical activity and specific types of cancer.
They included studies of at least 10,000 adults that looked at physical activity and deaths from all causes, cardiovascular disease, and cancer; new cases of cardiovascular disease, coronary heart disease, stroke, and heart failure; all new cancers and 14 specific cancers.
They pooled the results of 196 studies of more than 30 million people, most of whom reported leisure time physical activity below 17.5 metabolic equivalent of task (MET) hours/week – equivalent to 300 minutes of moderate intensity physical activity. METs express the amount of energy (calories) expended per minute of physical activity, relative to energy expended at rest.
Appreciable population health benefits might be gained from increasing [physical activity] levels of people who are inactive to just half the current health recommendations ... [Leandro Garcia et al]
The evidence base was largest for deaths from all causes and new diagnoses of cardiovascular disease and cancer. In general, higher levels of weekly physical activity were associated with a lower risk of all outcomes, the analysis showed.
Differences in risk were greater between 0 and 8.75 weekly MET hours – equivalent to the recommended 150 minutes/week of moderate physical activity – with smaller marginal differences in risk above this level up to 17.5 MET hours/week.
Affects on cardiovascular disease and cancer
Associations were stronger for deaths from all causes and from cardiovascular disease than those from cancer. Compared with inactive adults, those clocking up 8.75 MET hours/week had 31 per cent and 29 per cent lower risks of death from all causes and from cardiovascular disease, respectively; the difference in the risk of death from any cancer was 15 per cent.
At 8.75 MET hours/week, the risk of cardiovascular disease was 27 per cent lower. But the associations were weaker for different types of heart disease, with the strongest reduction observed for coronary heart disease: 21 per cent lower risk.
The association was weaker for any diagnosis of cancer (12 per cent lower risk), but stronger for head and neck cancers, myeloid leukaemia, myeloma, and stomach (35 per cent to 22 per cent lower). Weaker associations were observed for lung, liver, womb, bowel and breast cancers (16 per cent to 5 per cent lower risk).
Conclusion
To contextualise the results, the researchers estimated the proportion of preventable deaths and disease outcomes at different levels of leisure time physical activity. They calculated that if all insufficiently active people had managed 8.75 MET hours/week, almost 16 per cent of all recorded premature deaths would have been prevented. Notably, 10 per cent of all deaths would have been prevented if everyone clocked up half this weekly target – in other words, just 75 minutes of moderate intensity physical activity.
The researchers acknowledge that the included studies relied on self-reported physical activity levels, and they sometimes had to make assumptions about the intensity and duration, where these were not reported explicitly.
But they conclude: ‘Appreciable population health benefits might be gained from increasing [physical activity] levels of people who are inactive to just half the current health recommendations, with further benefits for all reaching at least the recommended level, and smaller additional benefits beyond that.’
To read the full version of the article – titled Non-occupational physical activity and risk of cardiovascular disease, cancer and mortality outcomes: a dose–response meta-analysis of large prospective studies doi 10.1136/bjsports-2022-105669 – visit: https://bjsm.bmj.com/lookup/doi/10.1136/bjsports-2022-105669
Author: Ian A McMillan
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