Imma Perfetto
Cosmos science journalist
Plenty of studies have found that being physically active is associated with lower risk of cardiovascular disease and early death, but new research suggests that it may be more complicated than that.
A study which followed 22,750 Finnish twins over 3 decades investigated the links between their leisure time physical activity, and mortality, genetic disease risk, and biological ageing.
But, after adjusting for genetic and lifestyle-related factors, the researchers found that following an overall healthy lifestyle may be more beneficial than maintaining high levels of physical activity in your leisure time.
“The widely observed favourable association between physical activity and mortality are based on observational studies that are prone to bias from different sources,” says Dr Laura Joensuu from the University of Jyväskylä, co-author of the paper in the European Journal of Epidemiology.
“In our studies, we aimed to account for various sources of biases, and combined with the long follow-up period, we could not confirm that adhering to physical activity guidelines mitigates genetic cardiovascular disease risk or causally reduces mortality.”
The twins included in the study were born before 1958. Their level of physical activity was assessed 3 times over 15 years – in 1975, 1981, and 1990 – and they were followed until they died or until the end of 2020, whichever came first.
The data revealed 4 classes of physical activity: sedentary; moderately active; active; and highly active.
At the end of the study period, they found the greatest benefit was shown in the moderately active group which had a 7% lower risk of overall mortality compared to the sedentary group. A higher level of physical activity brought no additional benefit.
However, assessing the differences between short-term mortality (1990-2011) and long-term mortality (2012-2020), it revealed an interesting difference.
The higher the level of physical activity, the lower the mortality risk in the short term. But, in the long term, highly active people’s mortality did not differ from those who were more sedentary.
The researchers propose that, rather than physical activity reducing mortality risk, the ability to participate in physical activity during leisure time, and to increase it later in life, are instead indicators of underlying good fitness, health and healthy lifestyle.
“An underlying pre-disease state can limit physical activity and ultimately lead to death, not the lack of exercise itself,” says Elina Sillanpää, an associate professor from the University of Jyväskylä and corresponding author of the study.
“This can bias the association between physical activity and mortality in the short term.”
From blood samples, they also estimated the biological ageing rates of a subset of 1,153 twins using epigenetic clocks. This estimates the biological ageing based on DNA methylation levels, which regulate gene expression and change over time.
“We found that the association between leisure-time physical activity and biological aging was U-shaped: biological aging was accelerated in those who exercised the least and the most,” says Sillanpää.
However, other lifestyle-related factors, such as smoking and alcohol consumption, largely explained the association.
They conclude: “When considering biological ageing and all-cause mortality, following an overall healthy lifestyle may be more beneficial than maintaining high levels of leisure-time physical activity.”
