Abstract

This nationwide ecological study examined whether the availability of urban green infrastructure (UGI) and its seasonal dynamics are associated with age- and sex-specific suicide mortality rates across Türkiye. We delineated settlement polygons for all provincial and district centers. We paired them with Landsat-8-derived Normalized Difference Vegetation Index (NDVI) to compute annual, summer, and winter mean greenness and intra-annual NDVI variance for 2013-2019. We then assembled age- and sex-stratified suicide rates and nine provincial covariates from the socioeconomic, hydroclimatic, and air quality domains. Analyses included correlations, ordinary least squares with robust errors, optimal-scaling CAT-PCA, pooled PCA with principal-components regression, and canonical correlation analysis. The national mean urban NDVI was 0.124 (whole-province mean: 0.184). Total suicide showed no consistent bivariate association with greenness; however, clear life-course differences were observed between men and women. A higher mean NDVI was associated with lower suicide rates in adolescents and, to a lesser extent, in adults aged 20-39 years. However, the association was positive from age 40 onward. NDVI variance showed a mirror pattern—associated with higher suicide rates in youth but slightly lower rates in older adults—suggesting that both the amount and seasonality of vegetation have age-specific associations with suicide rates in this Turkish setting. Multivariable models supported these gradients: provinces with warmer climates, greater greenness, and seasonally stable vegetation tended to have lower adolescent suicide rates but higher mid-to-late life suicide rates. Temperature variability was the only environmental factor positively associated with suicide across all age-sex strata. These ecological associations are consistent with the age-dependent relationship between UGI and suicide and may help generate hypotheses for age-targeted prevention strategies. However, the cross-sectional, province-level design precludes any causal inference.

Key words: Suicide, adolescence, aging, urban health, remote sensing, Türkiye