Objectives: Evaluate differences in depressive symptoms, compare sociodemographic and health-related variables associated with depressive symptoms and report level of impact of depressive symptoms on daily activities.
Methods: Cross-sectional study using a self-administered questionnaire and Patient Health Questionnaire-9 (PHQ-9) diagnostic survey on 1115 patients aged 60-93 years who attended a primary care clinic in Korea, Russia or USA.
Results: At least mild depression (PHQ-9 score of ≥ 5) occurred in 28% of Koreans, 65% of Russian and 27% of US participants. Russians scored more depressed on all PHQ-9 items (P < 0.01) and more suicidal thoughts (P < 0.001), while Koreans had less feelings of worthlessness (P < 0.001). Depression predictors included poorer self-rated health [odds ratio (OR) 2.47, 95% confidence interval (CI) 1.84-3.33, P < 0.0001], chronic diseases (OR 1.34, CI 1.21-1.48, P < 0.0001), female gender (OR 1.56, CI 1.15-2.12, P = 0.0046) and religious attendance (OR 0.88, CI 0.79-0.97, P = 0.0099) for all subjects. Being employed was protective in Korea (OR 0.41, CI 0.21-0.77, P = 0.0061) and being married (OR 0.42, CI 0.27-0.66, P = 0.0002) and of older age (OR 0.95, CI 0.93-0.98, P = 0.0006) protective in US participants. Vascular disease was associated with depressive symptoms in Russia (OR 3.47, CI 1.23-9.80, P = 0.0187). In regression analyses stratified by country for a given level of depressive symptoms, the Russian sample had less impact on daily activities (Russia R (2) = 0.107 versus Korea R (2) = 0.211 and US R (2) = 0.419) P = 0.029.
Conclusions: Depressive symptoms were more common in Russia than in Korea and USA but had less impact on daily functioning. Cultural or environmental factors may account for this finding.