After a mean follow-up of 13 years, Swedish men who had moderate levels of physical activity had a lower risk of heart failure compared with those who had high or low activity levels, according to a population-based cohort study.

Lead researcher Iffat Rahman, PhD, of the Karolinska Institutet in Stockholm, and colleagues found that walking or bicycling for at least 20 minutes per day was associated with the largest risk reduction for heart failure. They published their findings online in the Journal of the American College Cardiology: Heart Failure on Aug. 12.

Approximately 23 million people worldwide and more than 5.8 million people in the U.S. have heart failure.

The researchers examined the Cohort of Swedish Men study, which enrolled participants in 1997 and 1998. At baseline, the average age of the men was 60.

The trial included men born between 1914 and 1948 who lived in two Swedish counties. They were asked to complete a questionnaire about their physical activity, diet, anthropometric traits and other lifestyle factors. The questionnaire also included information on education, smoking and alcohol consumption, height, weight and family history of MI.

After excluding participants who had heart failure or MI at baseline and those who were missing physical activity data, the researchers evaluated 33,012 men.

During the follow up period, there were 3,609 heart failure events, including 3,190 heart failure hospitalizations and 419 heart failure deaths.

Compared with participants who had median levels of activity, participants who had extremely high (defined as 57 metabolic equivalents per day) and extremely low (38 metabolic equivalents per day) had a 51 percent and 47 percent increased risk of heart failure, respectively.

The researchers noted that walking, bicycling or exercising more than an hour per week was associated with a reduced risk of heart failure. However, physical inactivity was not associated with heart failure development.

The study had a few limitations, according to the researchers. The participants self-reported their physical activity, so they may have overestimated or underestimated the information. The results also may not be generalizable to the general population because the study enrolled middle-aged and elderly white men. The design of the study was also not ideal.

“It is important to note that we cannot infer on causality based on our study results,” the researchers wrote. “It is possible that the association between [physical activity] and risk of future [heart failure] could have been due to unmeasured confounders or residual confounding both at baseline and during the follow-up period.”