One in 10 early deaths could have been prevented if everyone had met just half the recommended weekly target of 150 minutes of moderate intensity physical activity, indicates the largest pooled data analysis of its kind, published online in the British Journal of Sports Medicine.
Just 75 minutes a week substantially reduces the risks of early death, cardiovascular disease, and certain cancers, including those of the head and neck and myeloid leukaemia, 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.
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.
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.
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% and 29% lower risks of death from all causes and from cardiovascular disease, respectively; the difference in the risk of death from any cancer was 15%.
At 8.75 MET hours/week, the risk of cardiovascular disease was 27% lower. But the associations were weaker for different types of heart disease, with the strongest reduction observed for coronary heart disease: 21% lower risk.
The association was weaker for any diagnosis of cancer (12% lower risk), but stronger for head and neck cancers, myeloid leukemia, myeloma, and stomach (35% to 22% lower). Weaker associations were observed for lung, liver, womb, bowel and breast cancers (16% to 5% lower risk).
To contextualize 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% of all recorded premature deaths would have been prevented. And notably, 10% 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 weren't explicitly reported.
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."
Garcia, L., et al. (2023) Non-occupational physical activity and risk of cardiovascular disease, cancer and mortality outcomes: a dose–response meta-analysis of large prospective studies. British Journal of Sports Medicine.doi.org/10.1136/bjsports-2022-105669.