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

•Subjects with small social networks had a persistent unhealthy risk factor profile.•Social network size was associated with alcohol use, smoking and physical activity.•The observed association was independent of gender, age and education.

ObjectiveTo determine the associations between social network size and subsequent long-term health behaviour patterns, as indicated by alcohol use, smoking, and physical activity.MethodsRepeat 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.ResultsParticipants 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.ConclusionsSocial network size predicted persistent behaviour-related health risk patterns up to at least two decades.