Loneliness, Social Isolation, and Chronic Disease Outcomes

BACKGROUND: Research suggests that loneliness and social isolation (SI) are serious public health concerns. However, our knowledge of the associations of loneliness and SI with specific chronic diseases is limited. PURPOSE: The present prospective cohort study investigated (a) the longitudinal associations of loneliness and SI with four chronic diseases (cardiovascular disease CVD, chronic obstructive pulmonary disease COPD, diabetes mellitus Type 2 T2D, and cancer), (b) the synergistic association of loneliness and SI with chronic disease, and (c) baseline psychological and behavioral explanatory factors. METHODS: Self-reported data from the 2013 Danish "How are you?" survey (N = 24,687) were combined with individual-level data from the National Danish Patient Registry on diagnoses in a 5 year follow-up period (2013-2018). RESULTS: Cox proportional hazard regression analyses showed that loneliness and SI were independently associated with CVD (loneliness: adjusted hazard ratio (AHR) = 1.20, 95% confidence interval CI; 1.03, 1.40; SI: AHR = 1.23, 95% CI 1.04, 146) and T2D (loneliness: AHR =1.90, 95% CI 1.42, 2.55; SI: AHR = 1.59, 95% CI 1.15, 2.21). No significant associations were found between loneliness or SI and COPD and cancer, respectively. Likewise, loneliness and SI did not demonstrate a synergistic effect on chronic disease. Multiple mediation analysis indicated that loneliness and SI had an indirect effect on CVD and T2D through both baseline psychological and behavioral factors. CONCLUSION: Loneliness and SI were independently associated with a diagnosis of CVD and T2D within a 5 year follow-up period. The associations of loneliness and SI with CVD and T2D were fully explained by baseline psychological and behavioral factors.