Upping exercise to 'just half the current recommendations' may help prevent mortality

Key takeaways:

• Exercising for 8.75 marginal metabolic equivalent of task-hours per week reduced mortality risk.
• Researchers said there may be “appreciable population health benefits” if inactive people hit half that target.

Exercising for 4.375 marginal metabolic equivalent of task-hours — which is half of the weekly recommendations — could have prevented 10% of premature deaths, according to researchers.

A plethora of previous research has shown that higher levels of physical activity are better for health outcomes, Leandro Garcia, DSc, MSc, BSc, a lecturer of complexity science in public health at Queen’s University Belfast, and colleagues wrote in the British Journal of Sports Medicine. But “differing methods used in previous meta-analyses limit comparability of relative risks across different outcomes,” they added.

Therefore, Garcia and colleagues conducted a systematic review and cohort-level dose-response meta-analysis “to quantify dose-response associations between nonoccupational physical activity and several CVD, cancer and mortality outcomes using a novel harmonization framework to overcome the challenges posed by different physical activity measurement methods,” they wrote.

This framework, they added, “allowed us to compare studies measuring and reporting physical activity in a wide variety of ways on the same activity exposure scale of marginal [metabolic equivalent task-hours (mMET-hours)] per week.”

“This meant we could be more inclusive of the available evidence than previous meta-analyses and we could explore the dose-response relationships between nonoccupational physical activity and nine site-specific cancers for the first time,” they wrote.

The researchers searched databases like PubMed, Scopus and Web of Science for prospective cohort studies that had three or more categories for physical activity; CIs for mortality or incident CVD, stroke, both total and site-specific cancers, heart failure and coronary heart disease; and a general population sample of at least 10,000 adults. They ultimately included 196 articles that covered 94 cohorts with more than 30 million participants.

Garcia and colleagues found inverse nonlinear dose-response associations, which they wrote indicate that, for sedentary adults, small increases in nonoccupational physical activity can offer significant protection from a variety of chronic disease outcomes.

In general, they found that higher levels of physical activity were linked to lower risks for all outcomes, but if all participants who were not active enough had achieved 8.75 mMET-hours per week of exercise — which is equivalent to the 150 minutes per week of moderate-to-vigorous aerobic physical activity that is currently recommended — then 15.7% (95% CI, 13.1-18.2) of all premature deaths would have been averted.

If patients hit just half that target, at 4.375 mMET hours per week, 10% of deaths could have been prevented.

The risk differences were greater between 0 and 8.75 mMET-hours per week, Garcia and colleagues wrote. There were smaller marginal risk differences up to 17.5 mMET-hours per week, but beyond that, additional differences were uncertain and small.

At 8.75 mMET-hours per week, the associations were stronger for CVD mortality (RR = 0.71; 95% CI, 0.66-0.77) and all-cause mortality (RR = 0.69; 95% CI, 0.65-0.73) compared with cancer mortality (RR = 0.85; 95% CI 0.81-0.89).

“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 and colleagues concluded.