A study of 1.2 million adolescents has found that fitness is associated with a lower risk of heart failure before age 50. The observational research published in the European Journal of Preventive Cardiology suggests that the protective effects of physical activity on the heart start early in life.

“Heart failure is generally considered an older person’s disease but our research team has found that incidence rates are increasing in people younger than 45 years of age,” said last author Professor Annika Rosengren, professor of internal medicine at the Sahlgrenska Academy, University of Gothenburg, Sweden.

She continued: “In a previous study using the Swedish Military Service Conscription Registry we showed that the risk of early heart failure was higher in overweight and obese adolescents.3 In the current study we used the same registry to investigate the impact of physical fitness on risk.”

The study investigated the association of cardiorespiratory fitness and muscle strength in adolescence with the risk of early heart failure. It included 1,226,623 Swedish men aged 18 years on average who were in compulsory military service between 1968 and 2005 and included in the Swedish Military Service Conscription Registry. On enrolment to the military, the men underwent strength and fitness testing and the results were recorded in the registry. Cardiorespiratory fitness was measured by a cycle ergometer test. Muscle strength was evaluated using the combination of knee extension, elbow flexion, and hand grip tests.

The researchers used the Swedish national inpatient registry, which includes all hospitalisations in the country, to find out which of the men had been hospitalised with a heart failure diagnosis between 1968 and 2014. During the 46 year follow–up period, 7,656 men had a first hospitalisation for heart failure. The average age at diagnosis was 50 years. High cardiorespiratory fitness and muscle strength were both associated with a lower incidence of heart failure.

After adjustment for factors that could influence the association, including body mass index (BMI in kg/m2), diabetes mellitus, hypertension, and blood pressure, those with low cardiorespiratory fitness had a 60% increased risk of heart failure compared to those with high cardiorespiratory fitness. Those with low muscle strength had a 45% increased risk of heart failure compared to those with high muscle strength.

“The conscript registry was a good dataset for studying risk factors for early heart failure because none of the participants were old,” said Professor Rosengren. “The oldest people in the registry were born in about 1950 so by the end of the study period in 2014 they were still under 65 years of age. We found that if you were very fit when you were young, you had a lower risk of having heart failure before the age of 50 years.”

Several comorbidities are associated with or cause heart failure. The researchers investigated the links between fitness, strength, and heart failure associated with: congenital heart disease and acquired valve disease; coronary heart disease and/or diabetes and/or hypertension; and cardiomyopathy. The highest risk was observed for heart failure associated with coronary heart disease, diabetes or hypertension.

Professor Rosengren said: “Coronary heart disease, diabetes and hypertension are very affected by lifestyle behaviours. It appears that heart failure which is rooted in a condition that depends on lifestyle is most affected by fitness and strength.”

“This was an observational study so we can’t definitively conclude that people who work out more will avoid heart failure,” she added. “But our results may suggest that people who have a healthy lifestyle and are physically active throughout life are less likely to develop heart failure.”