The benefits of adolescent fitness for future cardiovascular health are probably overestimated

There is a well-known link between good physical fitness at a young age and a lower risk of cardiovascular disease later in life. However, when the researchers adjusted for family factors using sibling analyses, they found a weaker association, although the association between high body mass index (BMI) and cardiovascular disease remained strong.

The study, “Genetic and Environmental Factors and the Risk of Cardiovascular Disease in Adolescents,” was conducted by researchers from the Karolinska Institute and other universities. It was published in JAMA Network Open.

“This does not mean that fitness is unimportant,” says the study’s last author Viktor Ahlqvist, a doctoral candidate in the Department of Global Public Health, Karolinska Institutet. “We could still see an association, although it was weaker after accounting for factors shared by full siblings.” We also think that adolescence is an important time in life to establish good habits such as exercise and healthy eating.”

Many observational studies have previously shown an association between various risk factors in youth and cardiovascular disease in adulthood. However, it is difficult to prove whether associations are causal because of the potential influence of unaccounted for genetic and environmental factors.

A collaborative team including researchers from the Karolinska Institute in Sweden therefore sought to examine whether a large proportion of cardiovascular disease in adulthood could indeed be prevented by lower BMI, lower blood pressure, improved physical fitness or improved muscle strength in adolescence.

By obtaining data from the Swedish military registry and other Swedish registries, the researchers identified over one million 18-year-old men and followed them for 60 years. Almost half of them were full brothers.

“The strength of our study, which makes it more reliable than many other conventional observational studies, is that we used sibling analyses,” says study first author Marcel Ballin, a researcher at Uppsala University and an analyst at the Stockholm Region Center for Epidemiology and Community. Medicine.

“That way we could examine how the relationship changes when controlling for all shared sibling factors. This includes environmental factors such as childhood environment and half of genetics.”

A high BMI is a strong risk factor

The results show that high BMI in late adolescence was strongly associated with future cardiovascular disease, even after the researchers controlled for shared family factors. However, the association between physical fitness and cardiovascular disease was significantly weaker in sibling analyses, suggesting that many previous observational studies may have overestimated the importance of adolescent fitness for cardiovascular health later in life.

“Our conclusion is that of the risk factors that have been studied, high BMI is the strongest individual risk factor for cardiovascular disease, and that efforts to tackle the obesity epidemic should continue to be a high priority,” says co-author Daniel Berglind, an assistant professor in the Department of for Global Public Health, Karolinska Institutet.

“A good level of fitness and muscle strength in adolescence does not seem so crucial, but physical activity still remains important for public health, as it can bring other health benefits.”

A few limitations

The study examined the association between risk factors in youth and future cardiovascular disease; other disease outcomes were not examined. The researchers did not have data on whether the participants’ risk factors varied later in life, and they only studied men, making it difficult to extend their findings to women.

The Military Service Registry also lacks details on certain risk factors for future cardiovascular disease, such as diet, alcohol consumption, smoking, blood lipids and blood glucose.