PM2.5-Associated Hospitalization Risk of Cardiovascular Diseases in Wuhan: Cases Alleviated by Residential Greenness

Abstract

PM2.5, a type of particulate matter with an aerodynamic diameter of less than 2.5 μm, is associated with the occurrence of cardiovascular diseases (CVDs), while greenness seems to be associated with better cardiovascular health. We identified 499,336 CVD cases in Wuhan's 74 municipal hospitals between 2017 and 2019. A high-resolution PM2.5 model and a normalized difference vegetation index (NDVI) map were established to estimate individual exposures. The time-stratified case-crossover design and conditional logistic regression models were applied to explore the associations between PM2.5 and CVDs under different levels of environmental factors. Greenness could alleviate PM2.5-induced hospitalization risks of cardiovascular diseases. Compared with patients in the low-greenness group (ER = 0.99%; 95% CI: 0.71%, 1.28%), patients in the high-greenness group (ER = 0.45%; 95% CI: 0.13%, 0.77%) showed a lower increase in total CVD hospitalizations. After dividing the greenness into quartiles and adding long-term PM2.5 exposure as a control factor, no significant PM2.5-associated hospitalization risks of CVD were identified in the greenest areas (quartile 4), whether the long-term PM2.5 exposure level was high or low. Intriguingly, in the least green areas (quartile 1), the PM2.5-induced excess risk of CVD hospitalization was 0.58% (95% CI: 0.04%, 1.11%) in the long-term high-level PM2.5 exposure group, and increased to 1.61% (95% CI: 0.95%, 2.27%) in the long-term low-level PM2.5 exposure group. In the subgroup analysis, males and participants aged 55-64 years showed more significant increases in the PM2.5-induced risk of contracting CVDs with a reduction in greenness and fine particle exposure conditions. High residential greenness can greatly alleviate the PM2.5-induced risk of cardiovascular admission. Living in the areas with long-term low-level PM2.5 may make people more sensitive to short-term increases in PM2.5, leading to CVD hospitalization.