Loneliness, unhealthy lifestyle, and incident cardiometabolic disease among middle-aged and older adults across 33 countries: a multicohort study

AIM: Loneliness is common in ageing population, we aim to identify the association between loneliness and cardiometabolic disease (CMD) across diverse settings, particularly cardiometabolic multimorbidity, and investigate whether unhealthy lifestyles and socioeconomic status (SES) help explain or amplify their relationships. METHODS: Data were obtained from six cohort studies across 33 countries, including the China Health and Retirement Longitudinal Study (CHARLS), English Longitudinal Study of Ageing (ELSA), Health and Retirement Study (HRS), Survey of Health, Ageing and Retirement in Europe (SHARE), Korean Longitudinal Study of Aging (KLoSA), and Mexican Health and Aging Study (MHAS). Eligible participants were aged 45 years or older. We applied time-varying Cox mixed-effects regression models to evaluate the association between loneliness and incident cardiometabolic diseases. The mediation role of unhealthy lifestyles and the joint effects of socioeconomic status, unhealthy lifestyles, and loneliness on incident cardiometabolic disease outcomes were also explored. RESULTS: Among 81978 participants, with a median follow-up of five years, 15750 participants developed CMD. Loneliness was associated with higher risk of any CMD (aHR 1.23, 95% CI 1.20-1.26), with a stronger association for multimorbidity (aHR 1.48, 1.37-1.60) than for single CMD (aHR 1.18, 1.15-1.22). Unhealthy lifestyles mediated 5.19% (95% CI: 3.06, 7.64) of the association with any CMD. Individuals experiencing a combination of low SES, multiple unhealthy lifestyle factors, and loneliness demonstrated the greatest cardiometabolic disease risk (adjusted HR: 1.89, 1.76, 2.02). CONCLUSIONS: Building on prior evidence that has largely come from single-cohort studies, our findings highlighted loneliness as a global risk factor in predicting the incident CMD, particularly cardiometabolic multimorbidity. The greatest risk was observed among socioeconomically disadvantaged individuals with multiple unhealthy lifestyles. These findings underscore the need to address synergistic risk of socioeconomic disadvantage, loneliness, and unhealthy lifestyle in multicomponent health interventions.