Reducing time spent sedentary and replacing it with even light movement or walking reduces overall mortality risk, according to new research*.
Writing in the BMJ scientists from the Norwegian School of Sport Sciences reviewed eight studies encompassing a total of more than 36,000 people with an average age of almost 63 years. Participants were followed for about five to six years; 2,149 deaths were recorded. The team found a greater volume of activity overall was linked to a lower risk of death. The results held for different intensities of activity.
“It is important for elderly people, who might not be able to do much moderate-intensity activity, that just moving around and doing light-intensity [activity] [will have] strong effects and is beneficial,” said Professor Ulf Ekelund, the study's lead author.
Crucially, all the studies involved monitoring the physical activity of individuals who had activity trackers, and the studies did not rely on self-reporting, which, the experts noted, could be unreliable. For each study, participants were split into four equal-sized groups, based on the total amount of time spent active, and the risk of death assessed, taking into account factors such as age, sex, body-mass index, and socioeconomic status. This was then repeated for an amount of activity at different levels of intensity. The results were analysed together to give an overview.
Compared with those who managed the least light physical activity, of about 200 minutes a day, those who clocked up about 258 minutes a day had a 40% lower risk of death, and those who managed about 308 minutes had a 56% lower risk.
Meanwhile, the group with the highest levels of light physical activity – achieving about 380 minutes a day – had a 62% lower risk of death than the group that did the least. The team noted that this was about twice as big an effect as previously thought, possibly due to more accurate data collection.
They introduce a note of caution given the study's limitations. It only looked at the situation for middle age and older adults, most of whom lived in the US or Europe, and some of the effect could be due to those people with a higher risk of death being less likely to engage in physical activity. Physical activity levels also were only measured over one period of time.
They conclude: "Higher levels of total physical activity, at any intensity, and less time spent sedentary, are associated with substantially reduced risk for premature mortality, with evidence of a non-linear dose-response pattern in middle aged and older adults."
*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