Suitable for teenagers to live longer? New research says maybe not

A new study from Uppsala University calls for decades of research to question, suggesting that physical health in young people can lead to longer lifespans.

Large-scale analysis of more than 1.1 million Swedish men found that highly suitable adolescents also reduced the risk of dying from illness and random accidents, suggesting that the frequently reported health benefits of early health may be greatly exaggerated. This surprising finding, published in the European Journal of Preventive Cardiology, reveals broad biases in previous studies that could reshape public health approaches to fitness promotion.

Researchers tracked Swedish men in military recruitment aged 18 to 60 and studied their adolescent fitness levels associated with premature deaths of various causes. Although the results initially seem to confirm previous studies – showing that the most suitable all-cause mortality rate for young people is 53% lower than the risk of the least disagreement, the study took an innovative approach by analyzing deaths from random accidents.

The same fitness protection against random accidents?

The research team led by Marcel Ballin used a method called negative control outcome analysis to test whether fitness actually provides the health protection many of the studies claim. They examined deaths in accidents such as car accidents, drowning and homicides – which should theoretically have a small connection to adolescent fitness levels.

The results were astonishing: Men with the highest fitness level had a 53% lower risk of dying in random accidents compared to those with the lowest adaptive men, and a lower risk of reducing all-cause mortality compared to those with the lowest adaptive men.

“We found that people with premature death in late adolescence had a lower risk of premature death compared to those with lower fitness levels. However, when we looked at their risk of dying in random accidents, we found almost similar strong associations.”

This unexpected finding suggests that highly suitable and less suitable individuals may differ in important ways beyond their cardiovascular capacity – these differences have not been fully considered by previous studies.

Brothers and sisters have strengthened the case

To further test their hypothesis, the researchers compared siblings with different fitness levels. This approach controls common family factors such as genetics, behavioral and environmental conditions.

Even when comparing brothers, this pattern remains: highly fit men have a lower risk of death to disease and random accidents, although the overall association is a little weaker than the general population analysis.

“It surprised us that even though we controlled for all the factors shared by siblings, the association with unexpected mortality reflected other associations. This highlights how strong the assumptions you made in observational studies are, as it seems difficult to create comparable groups,” Ballin notes.

Redefine expectations for fitness interventions

The study tracked specific mortality rates among 1.1 million participants and found:

• The most suitable group for cardiovascular mortality has decreased by 58%
• The most inappropriate group has a 31% reduction in cancer mortality rate
• All-cause mortality risk was reduced by 53% for the most inappropriate group
• Accidental mortality rate decreased by 53% for the Winning Festival with the least suitable group

A comparable reduction in risk of accidental death suggests what statisticians call “residual confusion” – there are statistical or unmeasurable differences between study groups that produce misleading correlations between study groups.

What might these differences be? More adaptable individuals usually come from higher socioeconomic backgrounds, have different behavioral patterns, and may have genetic characteristics that enhance health abilities and reduce disease risk. Even with complex statistical adjustments, these factors seem difficult to fully consider.

Is exercise still important?

Should these findings prevent physical exercise? Bahrain emphasizes this: “Our results should not be explained as if physical exercise and exercise are ineffective, or you should not try to improve it. Instead, to have a more nuanced understanding of the impact of fitness actually on different outcomes, we need to use several different approaches.”

The study is consistent with previous twin studies and genetic studies, which suggests overlapping genetic factors that affect both fitness ability and disease risk. There is growing evidence that adaptive protective effects may be smaller than generally believed.

Why is this important? Public health plans and policies require accurate estimates of potential benefits to correctly allocate resources. As Ballin explains, “large-scale interventions or policy changes designed to apply to the population as a whole must be based on reliable estimates, otherwise the risk of an expected impact has actually been overestimated.”

The researchers believe that future studies should use a variety of methods for triangulation results, including off-road comparisons, negative controls, sibling and twin comparisons, and various types of instrument variable analysis to establish more reliable estimates of adaptability.

Although routine physical exercise remains important for many health reasons, this study provides valuable reminders of the complexity of human health outcomes and the care required to explain observational research. As science continues to refine our understanding of health and longevity, the most accurate conclusion is that the relationship between cardiopulmonary health and long-term health during adolescence is more nuanced than previously thought.