Association between lifestyle inflammation score and quality of life according to depressive symptom status: a cross-sectional study in the Republic of Korea

Objectives: This study examined the association between lifestyle inflammation score (LIS) and health-related quality of life, assessed using the EuroQol-5 Dimensions (EQ-5D) index, among adults in the Republic of Korea. It also evaluated whether depressive symptoms moderated this association. Methods: Data from the 2024 Community Health Survey were analyzed, and 231,386 adults were included. LIS was calculated by integrating smoking, alcohol consumption, physical activity, and body mass index. The dependent variable, quality of life, was assessed using the EQ-5D index. Depressive symptoms, the moderator variable, were assessed using the Patient Health Questionnaire-9, with a score of ≥10 indicating depressive symptoms. Data were analyzed using complex-sample multivariable linear regression to examine interaction effects according to depressive symptom status, followed by simple-slope analyses. Results: After adjustment for demographic and health-related variables, LIS was significantly and negatively associated with the EQ-5D index (β=-0.0069, p<0.001), indicating that higher levels of inflammation-related lifestyle behaviors were associated with poorer quality of life. Depressive symptoms significantly moderated the association between LIS and the EQ-5D index (β=-0.01727, p<0.001). Simple-slope analyses showed that the adverse association between LIS and quality of life was stronger among individuals with depressive symptoms (β=-0.02349) than among those without depressive symptoms (β=-0.00621). Conclusion: Inflammation-related lifestyle behaviors were associated with reduced quality of life, and this negative association was stronger among individuals with depressive symptoms. These findings suggest that considering both lifestyle-related inflammatory burden and depressive symptoms may help explain population-level differences in quality of life.