Characteristics of Social Networks and Mortality Risk: Evidence From Two Prospective Cohort Studies

The size of social network is linked to health and longevity, but it is unclear whether the number of strong or weak social ties is most influential for health. We examined social network characteristics as predictors of mortality in the Finnish Public Sector (n = 7,617) and the Health and Social Support (n = 20,816) studies. Social network characteristics were surveyed at baseline in 1998. Information about mortality was obtained from the national death registry. During a mean follow-up of 16 years participants with a small social network (≤10 members) were more likely to die than those with a large social network (≥21 members) (adjusted hazard ratio (HR) = 1.23, 95% confidence interval (CI): 1.04, 1.46). Mortality risk was increased among participants with small number of both strong (≤2 members) and weak ties (≤5 members) (hazard ratio = 1.55, 95% confidence interval: 1.26, 1.79), and among those with large number of strong ties and small number of weak ties (hazard ratio = 1.28, 95% confidence interval: 1.08, 1.52), but not among those with small number of strong ties and large number of weak ties (HR = 1.04, 95%CI: 0.87, 1.25). These findings suggest that in terms of mortality risk the number of weak ties may be an important component of social networks