Tracking of risk factors for coronary heart disease from adolescence to young adulthood with special emphasis on physical activity and fitness. A longitudinal study.

Physical activity (PA), fitness and selected coronary heart disease (CHD) risk factors were studied in 2 Danish adolescent cohorts; changes in PA and fitness from the age of 16-18 years were measured in a subgroup of high school children; changes in lifestyle, fitness level and coronary heart disease risk factors were measured from late adolescence to young adult hood in a random sample of subjects attending school at baseline. Risk factors and physical fitness tracked from adolescence to young adulthood. The proportion of subjects in the upper quintile of risk still being in the upper quintile 8 years later was 2-3 times the expected in most risk factors. No relationship was found between physical activity and coronary heart disease risk factors in the adolescent population, and only a weak, but highly significant, relationship was found between VO2max and blood pressure in the large cohort of 17 year olds. These weak relationships could result from a relatively high fitness level and a small variation in fitness level in the young Danish population. Because of a great statistical power in the group of subjects at the same age from population 2, it was possible to analyze the relationship between blood pressure and fitness further. Lower blood pressure was found with higher fitness level, but only VO2max, and not physical activity, related to blood pressure, and the relationship became weaker with higher fitness level. In the adult male population, the variations in both VO2max and risk factors were much larger and a great number of the men had become sedentary. Inactive lifestyle was associated with low educational level, and the decrease in fitness and increase in coronary heart disease risk factor levels were more distinct in the former trade and vocational students than in the 'gymnasium' students. In the 17-year-old cohort, lower blood pressure was found with higher VO2max until a level of 53 and 45 ml.min-1.kg-1 in boys and girls, respectively, but above these levels no relationship was found between VO2max and blood pressure.