Interplay between mental health, greenness, and environmental factors in cardiovascular mortality: insights from AIR-MIND

Abstract

Aims The impact of the external exposome and mental health on cardiovascular diseases (CVDs) is well documented. However, the interactions between these factors remain poorly understood. This study aims is to assess the long-term impact of the exposome on cardiovascular and mental health and to explore the interactions between them. Methods and results 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 particulate matter with diameter < 2.5 μm (PM2.5), nitrogen dioxide (NO2), and carbon monoxide (CO) and per 1 µg/m3 for sulfur dioxide (SO2). 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), and 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). Five per cent 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 modifying effect depending on the pollutant, but were generally associated with risk reduction. Conclusion 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. Socioeconomic status 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. Registration ClinicalTrials.gov: NCT05198492 Lay summary What is known Air pollution is a well-established risk factor for cardiovascular diseases (CVDs). Growing evidence also links environmental exposures to mental health deterioration. What is new This study demonstrates that mental health, greenness, and socioeconomic status may modify the CVD risk associated with exposure to ambient air pollution. Access to mental health services, through improvement of mental health, may be associated with the lower risk of CVD-related mortality. Moreover, greater access to mental health service may attenuate the detrimental association between exposure to air pollution and CVD-related mortality. Socioeconomic status and greenness exposure may exert heterogeneous modifying effects on the relationship between environmental exposures and health outcomes, yet they generally appear to confer a protective effect, contributing to overall risk reduction. Potential use in clinical or public health practice These findings underscore the need for integrated environmental and mental health strategies in public health planning. High-resolution data on mental service use may serve as a marker of population vulnerability to environmental risk. Context-specific urban planning, emphasizing accessible green infrastructure and targeted interventions in socioeconomically disadvantaged regions, may mitigate the combined impact of air pollution and mental health burden on cardiovascular mortality.