Reassessing adolescent fitness impact on future cardiovascular health

The study aims to critically assess the commonly held belief regarding the benefits of adolescent fitness on future cardiovascular health. Despite widespread assumptions about the positive impact of physical activity during adolescence, this research investigates the possibility of overestimating the expected benefits.

While it’s widely believed that being fit in youth lowers the chance of heart issues later on, a recent study by researchers, including those from Karolinska Institutet, found a twist. The connection wasn’t as strong when they considered family factors using sibling analysis, which could have been stronger. Surprisingly, a high body mass index (BMI) is strongly linked to cardiovascular disease. This study’s findings were published in JAMA Network Open.

The study’s last author, Viktor Ahlqvist, a doctoral student at the Department of Global Public Health, Karolinska Institutet, said, “This does not mean that fitness is irrelevant. “We could still see an association, although it was weaker after considering factors shared by full siblings. We also think that adolescence is important for establishing good habits such as exercising and having a healthy diet.”

Past studies showed connections between young habits and adult heart problems. However, proving if these are causes is tricky due to hidden genetic and environmental factors. A team, including researchers from Karolinska Institutet, aimed to see if better adolescent habits, like maintaining a healthy weight, lower blood pressure, and being fit, could prevent many adult heart diseases.

Using data from the Swedish Military Conscription Register and other registries, researchers tracked over a million 18-year-old males for 60 years. Almost half were brothers. Unlike many studies, they used sibling analysis, considering shared factors like childhood environment and genetics. Results indicate a strong link between high BMI in late adolescence and future heart issues, even after adjusting for family factors. Surprisingly, the connection between physical fitness and heart health was weaker, suggesting that past studies overstated its importance.

Co-author Daniel Berglind, a docent at the Department of Global Public Health, Karolinska Institutet, said, “Our conclusion is that of the risk factors studied, high BMI is the strongest individual risk factor for cardiovascular disease, and that efforts to tackle the obesity epidemic should continue to be given high priority. A good level of fitness and muscle strength in adolescence doesn’t seem as crucial, but physical activity remains important for public health, as it can bring other health benefits.”

The study focused on links between early risk factors and future heart disease, excluding other health outcomes. Limitations include no information on participants’ changing risk factors over time, a male-only study group, and a lack of data on crucial factors like diet and smoking. The research had no specific funding, and one co-author has ties to certain organizations, though unrelated to the study. No other conflicts of interest were reported.

In conclusion, the study sheds light on the potential overestimation of the benefits of adolescent fitness on future cardiovascular health. While physical activity remains an essential component of a healthy lifestyle, a more nuanced understanding incorporating genetic and environmental factors is crucial for developing targeted and effective interventions to promote adolescent cardiovascular health.

Journal reference:

1. Marcel Ballin, Martin Neovius, et al., Genetic and Environmental Factors and Cardiovascular Disease Risk in Adolescents. JAMA Network Open. DOI: 10.1001/jamanetworkopen.2023.43947.