Loneliness, Chronic Conditions, and Healthcare Engagement in Japan: A Nationwide Cross-Sectional Study

Loneliness has been increasingly recognized as a determinant of adverse health outcomes, including mortality and cardiovascular disease, primarily based on evidence from Western countries. However, data from East Asian populations using standardized loneliness measures remain limited. This study aimed to examine the associations between loneliness, assessed using the University of California, Los Angeles (UCLA) 3-Item Loneliness Scale, and multiple health-related outcomes among adults in Japan.

We conducted a cross-sectional analysis using data from a nationwide, internet-based panel survey of the general population in Japan conducted in 2024. Participants aged 18-79 years were included. Loneliness was defined using the UCLA 3-Item Loneliness Scale. Primary outcomes were poor self-rated health and high symptom burden, assessed using the Somatic Symptom Scale-8. Weighted multivariable logistic regression models were used to estimate associations, adjusting for demographic, socioeconomic, and health-related factors, with additional adjustment for psychological distress.

Among 25,014 participants (mean [standard deviation {SD}] age, 50.0 [17.4] years; 49.9% men), 12,582 (50.3%) were classified as lonely. Loneliness was significantly associated with poor self-rated health (adjusted odds ratio [AOR], 2.71; 95% confidence interval [CI], 2.40-3.07) and high symptom burden (AOR, 3.61; 95% CI, 3.21-4.05). Loneliness was also associated with a higher prevalence of self-reported chronic diseases after adjusting for demographic, socioeconomic, and health-related factors; these associations were attenuated after further adjustment for psychological distress. In addition, lonely participants were less likely to report having a family doctor and demonstrated different patterns of engagement with preventive healthcare services.

Loneliness was associated with poorer perceived health, greater symptom burden, and altered healthcare-seeking behaviors, with attenuation after adjustment for psychological distress. These findings suggest that loneliness reflects health-relevant vulnerability beyond traditional risk factors and underscore the importance of addressing loneliness within population health strategies, even in healthcare systems with high accessibility.