Social isolation and cardiovascular disease: mediation by health behaviors and metabolic factors

Abstract Background Social isolation is associated with cardiovascular disease (CVD), the leading cause of death globally. Few studies have explored whether this connection is mediated by health behaviors or metabolic risk factors in a longitudinal design. Understanding the mechanism is important to confirm whether social isolation causes CVDs and to prevent the risk more effectively. Methods Employees of the City of Helsinki (Finland) who turned 40, 45, 50, 55, or 60 years old were invited to participate in a Phase 1 survey in 2000-2002, with follow-up surveys in 2007, 2012, 2017, and 2022. We used Bayesian predictive inference with logistic regressions to estimate the effect of social isolation (low social connections and support, singlehood, lack of memberships) at Phase 1 on CVD risk in Phases 3-5, with and without mediation by adverse health behaviors (physical inactivity, low fruit and vegetable consumption, short sleep duration, smoking, heavy alcohol consumption) or metabolic risk factors (obesity, diabetes, hypertension, hypercholesterolemia) reported in Phase 2. Results Among 3,919 participants (81% women, mean 49 years old at inclusion), a total of 846 (22%) reported CVD during the 15-year follow-up. The total effect of social isolation on the risk of CVD was RR (risk ratio) 0.97 (95% credible interval [CI] 0.75-1.20), and the indirect (mediated) effect through all mediators jointly was RR 1.01 (CI 0.98-1.03). Social isolation was associated with physical inactivity (prevalence ratio 1.68, CI 1.31-2.10) and smoking (PR 1.25, CI 1.05-1.48), and low social support with low fruit and vegetable consumption (PR 1.34, CI 1.10-1.62). Conclusions Neither the total nor mediated effects of social isolation on CVD risk were large in this population. Addressing social isolation should be considered when aiming to improve health behaviors. Key messages • Social isolation was not strongly associated with the risk of cardiovascular disease later in life either directly or through health behaviors or metabolic risk factors. • Social isolation was associated with lower physical activity and fruit and vegetable consumption and more smoking. Addressing isolation should be considered when aiming to improve health behaviors.