The effect of physical fitness on mortality is overestimated

Summary

Many observational studies have shown that people who exercise more and have good cardiorespiratory fitness early in life are at lower risk of premature death from causes such as cancer and cardiovascular disease. However, a new study published in the European Journal of Preventive Cardiology suggests that the association between physical fitness and a reduced risk of mortality may be misleading. “We found that people with high fitness levels in late adolescence had a lower risk of dying prematurely, for example from cardiovascular disease, compared to those with low fitness levels. But when we looked at their risk of dying in random accidents, we found an almost similarly strong association. This suggests that people with high and low fitness levels may differ in other important ways, which is something that previous studies have not fully taken into account,” says Marcel Ballin, associated researcher in epidemiology and lead author of the study. Based on conscription data from over 1 million menIn the study, the researchers leveraged data from 1.1 million Swedish men who were conscripted for military service between the years 1972 and 1995. The men, who were on average 18 years old at the time of conscription, were divided into five groups based on their fitness level at the time. They were then followed until their 60s or until they died. With access to the National Cause of Death Register, the researchers were able to see their cause of death. They subsequently used different methods to study the association between fitness level in late adolescence and premature death.The researchers started with a traditional analysis of mortality from cardiovascular disease, cancer and from all causes, as in previous observational studies. They adjusted their statistical models for factors such as BMI, age at conscription, year of conscription, and parents’ income and education level. The results showed that the group with the highest fitness level had a 58 per cent lower ris...