Social isolation and loneliness increase the risk of coronary heart disease: Insights from a prospective cohort study.

Social isolation and loneliness are associated with an increased risk of various diseases and all-cause mortality. Coronary heart disease (CHD) is the main cause of heart disease deaths worldwide, which affects people's quality of life and longevity. However, the causal relationship between social isolation, loneliness, and CHD remains uncertain. This study aims to explore the potential impacts of social isolation and loneliness on the risk of CHD, thereby helping identify those most susceptible to these conditions. A total of 442,811 individuals (mean and sd of age = 56.24 ± 8.07, 55.8% women, 91.5% white) were included in the study. The UK Biobank cohort study documented 25,120 CHD cases during a mean follow-up of 14.77 years. The relationship between loneliness, social isolation and CHD were first examined using the COX proportional risk model. A two-sample Mendelian randomization (MR) study was then conducted to further the association. We found that the hazard ratio (95% CI) of coronary heart disease (CHD) when comparing the most socially isolated groups to the least was 1.15 (1.05-1.26; P = 0.0017). Additionally, the hazard ratio (95% CI) for comparing the presence of loneliness to its absence was 1.15 (1.10-1.20; P < 0.001).Subgroup analyses showed that the risk of CHD was higher in individuals with low sleep quality who experienced social isolation and in women who experienced loneliness. MR analyses further revealed that individuals who felt lonely (OR = 1.03; 95% CI: 1.01,1.06) and those less involved in sports/social activities (OR = 1.02; 95% CI: 1.00,1.04) had a higher likelihood of developing CHD. MR provided further evidence supporting the causal relationship between social isolation, loneliness and CHD risk. Our findings suggest a significant association between social isolation, loneliness and increased risk of coronary heart disease. These findings suggest that both social isolation and loneliness are critical risk factors for CHD.