Researchers have slammed previous findings that have stated physical activity can reduce mortality risk.
A team of academics from Uppsala University are now calling this long-known belief ‘misleading’.
First author Marcel Ballin said: “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.”
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During the trial, the team of researchers analysed the health data of 1.1 million men from Sweden, all of whom were in the military between 1972 and 1995.
Each of the men were placed into a group dependent on their fitness level at the time of conscription. They were then assessed until they reached their 60s or until they died.
Men in the highest fitness level group were 53% less likely of dying from all causes compared to those in the other groups, the research has revealed.
As part of the investigation, the researchers also looked at how fitness is linked with death in random accidents, such as homicides, drowning and car accidents.
They discovered that men with the highest fitness levels were 53% less likely to die in random accidents, despite their fitness having no influence on their risk of dying in random accidents.
Using the sibling comparison design, the academics assessed the risk of premature death between siblings, looking at their fitness levels, environmental factors, behaviours and certain genetic factors.
Marcel Ballin explained: “It surprised us that the association with accidental mortality reflected the other associations, even after we controlled for all the factors that siblings share.
“This underlines how strong the assumptions are that you make in observational studies, since it appears to be very difficult to create comparable groups. The consequences may be that you overestimate the magnitudes of the effects you find.”
He added: “That the effects of good cardiorespiratory fitness may be overstated might sound controversial to some, but the fact is that if you look at the results from studies others than traditional observational studies, a more nuanced picture does emerge.
“A number of twin studies for example have found similar results. Some genetic studies also suggest that there are genes that affect both the propensity to be physically active or have a good fitness level, and the risk of developing diseases such as cardiovascular disease.”
He concluded: “Our results should not be interpreted as if physical activity and exercise are ineffective or that you should not try to promote it. But to create a more nuanced understanding of how big the effects of fitness actually are on different outcomes, we need to use several different methods.
“If we just ask the question in the same way, we will always get the same answer. It’s only when we get the same answer to a question that we have asked in slightly different ways that we can be sure that the findings are accurate.”
Read the study in the European Journal of Preventive Cardiology.
