Environmental determinants of cardiovascular-kidney-metabolic health: interactive roles of air pollution, heat waves, and green spaces.

BACKGROUND

Cardiovascular-kidney-metabolic (CKM) syndrome, characterised by linked metabolic, renal, and cardiovascular dysfunctions, confers high cardiovascular risk and represents a major public health concern in China. Environmental exposures such as air pollution, heat waves, and limited greenness may exacerbate cardiometabolic burden. Limited studies evaluated their independent and interactive effects on CVD risk among individuals with CKM syndrome.

METHODS

We assessed city-level annual environmental exposures using data from the China Health and Retirement Longitudinal Study 2011-2018. Specifically, we evaluated the effects of PM1, PM2.5, PM10, nitrogen dioxide (NO2), and heat waves on CVD incidence using Cox proportional hazards models, and examined multiplicative interactions via product terms. We quantified additive interactions using the relative excess risk due to interaction.

RESULTS

Exposure to air pollution (PM and NO2) and heat waves was associated with higher CVD risk, whereas a higher normalised difference vegetation index (NDVI) was protective from CVD. We observed significant interactions on both multiplicative and additive scales. Specifically, the joint association between PM and heat waves was greater than the sum of their individual risks (a positive additive interaction), suggesting that heat waves may exacerbate the risk associated with air pollution. Conversely, negative interaction terms involving NDVI suggested that higher greenness might modify the association between PM and CVD risk. These patterns were more pronounced in participants with advanced CKM stages.

CONCLUSIONS

Our findings provide novel evidence that multiple environmental stressors interact to influence CVD risk in the CKM population, highlighting the importance of integrated environmental and public health strategies.