Interplay Between Mental Health, Greenness, and Environmental Factors in Cardiovascular Mortality: Insights from AIR-MIND.

Background: The impact of the external exposome and mental health on cardiovascular diseases (CVD) is well documented. However, the interactions between these factors remain poorly understood.

Purpose: To assess the long-term impact of the exposome on cardiovascular and mental health and to explore the interactions between them.

Methods: This nationwide analysis encompassed 400 million person-years of observation, using individual health data. Environmental and socioeconomic status (SES) data were derived from environmental monitoring stations, satellite-based remote sensing, and national registries. Negative binomial regression was employed. Environmental and SES were assessed as modifiers using interaction terms and stratified analyses. The association between long-term exposure to air pollution (AP) and mortality was expressed as relative risks (RRs) with 95% confidence intervals (CIs), per 10 µg/m³ annual increase in PM₂.₅, NO₂, and CO, and per 1 µg/m³ for SO2.

Results: Between 2011 and 2020, 4,010,521 all-cause deaths were recorded, including 1,706,111 CVD-related deaths (42.5%), median age 81 (71-87), 53.6% were female. Annual increases in AP concentrations were associated with CVD mortality: PM₂.₅ (RR 1.023, 95% CI 1.012-1.035), NO₂ (RR 1.111, 95% CI 1.072-1.151), SO₂ (RR 1.081, 95% CI 1.030-1.134), and CO (RR 1.018, 95% CI 1.013-1.023); all p<0.001. Exposure to ambient pollutants was linked to higher rates of mental services (RR range: 1.003-1.053, all p<0.05). 5% increase in forestation index (RR 0.967, 95% CI 0.955-0.979, p<0.001) and recreational green spaces (RR 0.967, 95% CI 0.952-0.982, p<0.001) were directly associated with lower CVD mortality. With increasing rates of psychiatric hospitalizations and depression-related services, there was weaker association between exposure to AP and mortality, while greenness exposure and SES indicators showed a mixed modyfing effect depending on the pollutant, but were generally associated with risk reduction.

Conclusions: The findings indicate multidimensional interactions between AP exposure, mental health, and SES conditions in shaping mortality risk. Greater access to mental health services modified the effects of environmental exposures, attenuating the associated risk. SES and greenness exposure might be associated with heterogeneous modifying effects, but seem predominantly to reduce risk. Our study highlights the necessity for context-specific urban planning strategies that consider local environmental and health determinants.