Social networks and patterns of health risk behaviours over two decades : A multi-cohort study

Objective: To determine the associations between social network size and subsequent long-term health behaviour patterns, as indicated by alcohol use, smoking, and physical activity. Methods: Repeat data from up to six surveys over a 15- or 20-year follow-up were drawn from the Finnish Public Sector study (Raisio-Turku cohort, n = 986; Hospital cohort, n = 7307), and the Health and Social Support study (n = 20,115). Social network size was determined at baseline, and health risk behaviours were assessed using repeated data from baseline and follow-up. We pooled cohort-specific results from repeated-measures log binomial regression with the generalized estimating equations (GEE) method using fixed-effects meta-analysis. Results: Participants with up to 10 members in their social network at baseline had an unhealthy risk factor profile throughout the follow-up. The pooled relative risks adjusted for age, gender, survey year, chronic conditions and education were 1.15 for heavy alcohol use (95% CI: 1.06-1.24), 1.19 for smoking (95% CI: 1.12-1.27), and 1.25 for low physical activity (95% CI: 1.21-1.29), as compared with those with > 20 members in their social network. These associations appeared to be similar in subgroups stratified according to gender, age and education. Conclusions: Social network size predicted persistent behaviour-related health risk patterns up to at least two decades.Peer reviewe