Association between visits to blue spaces within walking distance and mental health among older adults in Japan: a cross-sectional study from the Japan Gerontological Evaluation Study

Abstract Background Exposure to blue spaces has been associated with better mental health, but most studies have focused on environmental proximity rather than actual use (frequency of visits and activity types) and have been conducted in Western countries. Evidence among older adults in Asian settings remains limited. This study examined the associations between frequency of visits to blue spaces within walking distance, activity types performed there, and mental health among older adults using data from 69 municipalities across Japan. Methods We conducted a cross-sectional analysis of 21,339 functionally independent adults aged ≥ 65 years from the 2022 Japan Gerontological Evaluation Study across 69 municipalities. Blue space visits and activity types were self-reported. Mental health outcomes included depressive symptoms, assessed using the 15-item Geriatric Depression Scale (score ≥ 5), and happiness (0–10 scale). Modified Poisson and linear regression were used, adjusting for demographic, socioeconomic, and health-related covariates, as well as urbanicity. Missing data were handled using multiple imputation. Sensitivity analyses included inland-only, dose–response, category-specific and complete-case analyses. Results Overall, 32.6% of participants reported visiting blue spaces at least once per month. Compared with non-visitors, visitors had a lower prevalence of depressive symptoms (prevalence ratio: 0.79; 95% CI: 0.74–0.84) and higher happiness scores (B: 0.28; 95% CI: 0.23–0.34). Similar associations were observed in inland municipalities. Among blue-space visitors, walking for health maintenance, viewing scenery, socializing with others, and commuting or running errands were associated with both a lower prevalence of depressive symptoms and higher happiness scores. In dose–response analyses, each additional monthly visit was associated with a lower prevalence of depressive symptoms and a higher happiness score. Conclusions Visits to blue spaces within walking distance were associated with better mental health among older adults. Designing blue-space environments that facilitate physical activity and social interaction warrants further evaluation as a potential strategy to support mental health in later life.