Loneliness and Cardiovascular Disease Risk: A Cross-National Study of Two Nationally Representative Cohorts of Older Adults in the US and South Korea

BACKGROUNDEpidemiological studies demonstrate higher loneliness is associated with increased risk of developing cardiovascular disease (CVD). However, most studies are conducted with populations in Western developed countries, whose cultures generally emphasize independence. Less clear is whether these associations are also evident in more interdependent cultures, such as those in East Asian countries. We hypothesized feeling lonely could be more stressful and exhibit stronger associations with CVD risk in a highly interdependent versus independent culture. METHODSWe examined associations of loneliness with fatal and non-fatal CVD incidence in older adults from the Health and Retirement Study (HRS; n =13,073) conducted in the U.S. and from the Korean Longitudinal Study of Aging (KLoSA; n=8,311) conducted in South Korea. In both cohorts, baseline loneliness was assessed using one item from the Center for Epidemiologic Studies Depression Scale. Incident CVD was defined as reporting new-onset CVD on the biennial questionnaire or CVD death reported by proxies. Within each cohort, we estimated adjusted hazard ratios (aHR) of incident CVD according to loneliness (yes/no) over 12-14 years of follow-up, adjusting for relevant baseline covariates, including social isolation, sociodemographic factors, health conditions, and health behaviors. We further examined health behaviors as a potential pathway underlying these associations using counterfactual mediation analyses. RESULTSControlling for all covariates, feeling lonely was associated with an increased likelihood of developing CVD in the U.S. (aHR:1.15, 95%CI: 1.04,1.27) and in South Korea (aHR: 1.16, 95%CI: 1.00, 1.34). The pooled analysis showed no heterogeneity (Q=0.009, p=0.92), and the HR for loneliness was 1.14 (95% CI: 1.05-1.23). Regarding potential mediators, several behaviors accounted for a proportion of the association: physical activity, in both countries (14.6%, p=0.03 in HRS; 1.3%, p = 0.04 in KLoSA), alcohol consumption only in KLoSA (1.1%, p < 0.001), smoking only in HRS (4.7%, p < 0.001). CONCLUSIONS AND RELEVANCEContrary to our hypothesis, the magnitude of the loneliness-CVD relationship was similar in both countries, with 14% higher odds of developing CVD, while behavioral pathways appeared different. Loneliness may be a risk factor for CVD regardless of culture; however, different prevention strategies in clinical settings may be required. Clinical PerspectiveWhat is New? O_LIEven after controlling for social isolation, health behaviors/conditions, and sociodemographic factors, feeling lonely was associated with an increased likelihood of developing CVD among older adults in both the U.S. (15% increase) and South Korea (16% increase). C_LIO_LIThe impact of loneliness on CVD risk did not appear to differ substantially by culture, comparing individuals from a more independent versus interdependent culture. C_LIO_LIThe behaviors linking loneliness and CVD differed somewhat between the U.S. and South Korea, suggesting cultural factors may contribute to shaping distinct behavioral pathways through which loneliness impacts health. C_LI What are the clinical implications? O_LIA consistent association between loneliness and CVD risk was evident in two very different cultures, suggesting loneliness may be a relevant target for CVD prevention strategies in diverse populations. C_LIO_LIWhile the associations are modest, the public health implications of loneliness-related CVD could be significant if a substantial portion of the population experiences loneliness, particularly in the aftermath of the COVID-19 pandemic. C_LIO_LIAssessing loneliness levels may provide healthcare professionals with greater insight into patients CVD risk. C_LI