BACKGROUND: Previous study revealed that social isolation and loneliness are associated with incident type 2 diabetes mellitus (T2DM). However, the long-term effects of social isolation and loneliness on the population with T2DM have not been known. This study aims to evaluate the potential associations of social isolation and loneliness with all-cause and cause-specific mortality in individuals with T2DM. METHODS: The prospective cohort study included 26 549 UK adults diagnosed with T2DM at baseline. Social isolation and loneliness were evaluated through a self-reported questionnaire. Mortality data was obtained from the National Death Registration Centre. RESULTS: During a median follow-up of 13.3 years (IQR: 12.5-14.2 years), 5467 (20.6%) participants died from all-cause, 1953 (7.4%) from cardiovascular disease (CVD) and 1569 (5.9%) from cancer. Social isolation could increase the risks of all-cause, CVD and cancer mortality (most vs least
adjusted HR (95% CI): 1.32 (1.22-1.42), 1.44 (1.26-1.65) and 1.19 (1.05-1.34), respectively). Similarly, loneliness significantly increased the risks of all-cause, and CVD mortality (yes vs no
adjusted HR (95% CI): 1.17 (1.07-1.28) and 1.26 (1.07-1.48)). In joint analyses, as the degree of social isolation intensified, there were concomitant rises in the risks of all-cause, and CVD mortality in the no-loneliness or loneliness subgroup (adjusted HR (95% CI): 1.4 (1.21-1.61) and 1.65 (1.29-2.11)). CONCLUSIONS: This study found that social isolation was significantly associated with the increased risks of all-cause, CVD and cancer mortality among individuals with T2DM. Loneliness was also associated with all-cause mortality and CVD mortality, but not cancer mortality. These findings highlight the importance of social isolation and loneliness management in patients with T2DM.