Objectives: The aim of the study was to analyse changes in coronary heart disease (CHD) risk factors from adolescence to young adulthood, and how changes in risk factors relate to changes in lifestyle.
Design: A randomized sample of school children was tested in 1983 and followed-up 8 years later. In 1983 a dropout of 0.7% was found and the sample was representative of 16-19-year-old Danes.
Subjects: Subjects followed-up 8 years later (two-thirds of the original sample) were 88 male and 115 female 15-19-year-old school children attending 18 high schools, nine vocational and nine trade schools, throughout Denmark.
Main outcome measures: Height, body weight, body fat, occupation and coronary heart disease risk factors including physical activity (PA), fitness, blood pressure (BP), serum cholesterol, HDL cholesterol, triglyceride (TG) and smoking habits were assessed.
Results: In males all risk factors increased: the increases in total cholesterol level and systolic and diastolic BP were large, 0.85 mmol l-1 and 11 mmHg, respectively. In females, the risk for some factors increased (total cholesterol and BP), others decreased (higher HDL cholesterol), and triglyceride did not change. Significant tracking was found in both sexes, with the highest correlation coefficients in men. A total risk score was calculated by categorizing risk factors into six groups--1 to 6--and then adding the scores. Pearson correlation between the total risk scores in 1983 and 1991 in men was r = 0.67 (P < 0.001). Only a weak association was found for the total risk score in women. Nearly 50% of the boys, who were initially in the upper quintile of risk, were still in the upper quintile 8 years later for most risk factors. In men, the changes in risk factors were related to social factors. Blue-collar workers and the unemployed had the highest increase in risk factors, and the largest decrease in VO2max (ml min-1 kg-1) when analysed together. In both sexes the best relationship between 1983 and 1991 values was found in body mass index (BMI). Leisure time physical activity (PA) and triglyceride (TG) had a low correlation between 1983 and 1991 values. Physical activity had a non-significant correlation over time for women, indicating that PA in 1983 did not predict PA in 1991 at all.
Conclusion: Coronary heart disease risk factors tracked in both males and females, but only in males was a strong relationship found for total risk from adolescence to young adulthood, indicating the influence of a poor lifestyle in high-risk men. Lower social status related to higher risk.