Objective: To determine whether clustering of biological cardiovascular disease (CVD) risk factors exists and to investigate the longitudinal relationship between lifestyle parameters (dietary intake, physical activity and smoking behaviour) and clustering of biological CVD risk factors, which was defined as belonging to one or more sex-specific 'high-risk' quartiles for the ratio between levels of total serum cholesterol and high-density lipoprotein cholesterol, diastolic blood pressure, body fatness (sum of four skinfolds) and cardiopulmonary fitness (number of laps accomplished on a 20 m shuttle-run test).
Methods: The study was part of the Northern Ireland Young Hearts Project, a 3-year observational longitudinal study concerning adolescent boys (n=229) and girls (n=230) who were initially aged 12 years. The longitudinal relationships were analysed with generalized estimating equations.
Results: Significant clustering of biological CVD risk factors was observed both for boys and for girls, but the stability over time was rather low. Smoking was the only lifestyle parameter related to this clustering and was observed only among girls (rate ratio 1.5, P < 0.01); furthermore, none of the lifestyle parameters was significantly related to this clustering.
Conclusions: Because biological CVD risk factors tend to cluster, it is important to investigate these risk factors together. However, for subjects in this age group, according to our analysis, lifestyle parameters were hardly related to this clustering.