High Aerobic Fitness in Late Adolescence Is Associated With a Reduced Risk of Myocardial Infarction Later in Life: A Nationwide Cohort Study in Men

Study Questions:

Signs of atherosclerosis are present in all large arteries already in adolescence. What is the association between high physical fitness in late adolescence and myocardial infarction (MI) later in life?

Methods:

A total of 743,498 Swedish men were examined at the age of 18 years at the time of army enrollment (1969-1984). Aerobic fitness (Wmax) and muscle strength were measured using standardized methods. MIs occurring in the cohort were tracked through national registers. During a median follow-up period of 34 years, 11,526 MIs were registered in the cohort.

Results:

After adjusting for age, body mass index (BMI), diseases, education, blood pressure, and socioeconomic factors, one standard deviation increase in the level of physical fitness (Wmax) was associated with an 18% decreased risk of later MI (hazard ratio [HR], 0.82; 95% confidence interval [CI], 0.80-0.85). The beneficial effects of Wmax were significant across all recognized BMI groups, ranging from lean (BMI <18.5 kg/m2) to obese (BMI >30 kg/m2) (p < 0.05 for all). However, obese men (BMI >30 kg/m2) in the highest fourth of Wmax had a higher risk of MI than did lean men (BMI <18.5 kg/m2) in the highest (HR, 4.6; 95% CI, 1.9-11.2), and lowest (HR, 1.7; 95% CI, 1.2-2.6) fourth of Wmax.

Conclusions:

There is a significant graded inverse association between aerobic fitness in late adolescence and MI later in life in men. However, obese men with a high aerobic fitness had a higher risk of MI than lean men with a low aerobic fitness.

Perspective:

The findings help dispel the myth that it is OK to be overweight if you are fit. Such studies are only possible in countries like Sweden who have been pioneers in promoting and measuring the value of exercise and fitness. All conscripts in Sweden underwent an electrically braked ergometer cycle test to assess aerobic fitness. Isometric muscle strength for knee extension, grip, and elbow flexion was measured in Newton (N) using dynamometers.

Clinical Topics: Sports and Exercise Cardiology

Keywords: Elbow, Myocardial Infarction, Body Mass Index, Sweden, Muscle Strength, Overweight, Physical Fitness, Socioeconomic Factors, Blood Pressure, Hand Strength


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