Adverse health conditions may serve as intermediate states linking loneliness and social isolation with excess mortality. We examined whether loneliness and social isolation are primarily associated with the risk of developing an adverse health condition or with prognosis after diagnosis.
A cohort of 236 879 individuals from the UK Biobank was followed from baseline in 2006–2010 until death or administrative end of follow-up in 2022. The incidence of three broad categories of adverse health conditions, (1) neoplasms, (2) endocrine, nutritional and metabolic diseases and (3) circulatory diseases, was recorded through self-report or register-based data. Progressive multistate Markov proportional hazards models were used to examine the associations of loneliness and social isolation with transitions from a healthy state to adverse health conditions and mortality, while adjusting for confounding.
Loneliness and social isolation were associated with all three transitions: from a healthy state to adverse health conditions (except for neoplasms), from a healthy state to mortality and from adverse health conditions to mortality. In transitions to adverse health conditions, the HRs were larger for loneliness (HR range 1.12–1.17 for loneliness, 1.05–1.08 for social isolation). In subsequent transitions to mortality, the HRs were larger for social isolation (1.05–1.13 for loneliness, 1.28–1.42 for social isolation).
While both loneliness and social isolation were associated with the onset and prognosis of adverse health conditions, our findings highlight the associations of social isolation, in particular, with mortality.