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TOPLINE:

Men with high cardiorespiratory fitness in adolescence had a small increase in the risk for atrial fibrillation (AF) early in life but larger reductions in the risk for non-AF cardiovascular disease (CVD) later on. Sibling comparisons showed that the long-term cardiovascular benefits outweighed the small increased risk for AF.

METHODOLOGY:

• Researchers conducted a cohort study to evaluate whether cardiorespiratory fitness in adolescence was associated with long-term risks for AF and other cardiovascular events.
• They included data of over 1.1 million Swedish men who underwent mandatory conscription testing at a mean age of 18.3 years between 1972 and 1995, who were followed through national health registers until December 2023.
• Cardiorespiratory fitness was measured at conscription with a maximal bicycle ergometer test, and men were divided into deciles, allowing comparison from the least fit to the most fit.
• The co-primary outcomes were the occurrence of AF and non-AF CVD such as stroke and ischemic heart disease.
• Researchers also analyzed 477,453 full brothers, comparing each man with his male sibling, to account for the influence of shared genetic, behavioral, and environmental factors.

TAKEAWAY:

• Overall, 45,179 men (4.0%) experienced AF at a median age of 54.8 years, and 96,404 (8.6%) experienced a non-AF cardiovascular event at a median age of 54.4 years.
• Men in the highest vs lowest decile of cardiorespiratory fitness had a 0.43% higher risk for AF by age 40 years and a 0.70% higher risk from age 45 years onwards. However, the risks for non-AF CVD were lower by 0.26% and 0.84%, respectively.
• By age 65 years, men in the highest vs lowest decile of cardiorespiratory fitness had a 3.42% higher risk for AF and an 8.11% lower risk for non-AF CVD.
• In sibling comparisons, higher cardiorespiratory fitness was linked to a reduced risk for non-AF CVD by age 35 years. The gap widened further by age 65 years, despite an increased risk for AF.

IN PRACTICE:

“High adolescent cardiorespiratory fitness is associated with a small excess in AF risk during early adulthood that is outweighed by larger reductions in non-AF CVD after controlling for familial confounders. These findings support population-level efforts to improve youth cardiorespiratory fitness and provide reassurance about the safety and benefits of high fitness levels,” the study authors wrote.

SOURCE:

This study was led by Marcel Ballin, PhD, of Uppsala University in Uppsala, Sweden. It was published online on May 21 in Circulation.

LIMITATIONS:

Findings may not be generalizable to women. Researchers could not adjust for alcohol use, smoking, body composition, or physical activity. Sibling comparison rested on assumptions such as no important nonshared confounders and no measurement error.

DISCLOSURES:

This study did not receive any specific funding. Several authors reported receiving various professional payments or affiliations, including employment at a government medical/regulatory agency, payments for expert opinions, lecture honoraria, and advisory-board fees from pharmaceutical and medical device companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.