The association of residential greenness and ambient particulate matter with hearing impairment in Chinese middle-aged and elderly adults: a nationwide cohort study

Objective

To examine the association of residential greening and atmospheric particulate matter (PM_2.5, PM₁₀) with the risk of hearing impairment in Chinese middle-aged and elderly adults.

Methods

Data from the China Health and Retirement Longitudinal Study (2011 to 2018 wave) were used. The degree of greening of residential areas were quantified using the Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS). PM concentrations were obtained from the CHAP dataset. Hearing impairment was self-reported by the participants. Cox proportional hazards models were used to assess the risk of hearing impairment associated with exposure to residential green spaces and PM. Additionally, the study investigated the potential modifying and mediating role between residential greenery, PM exposure and hearing impairment.

Results

A total of 13,585 participants aged 61.84 years (Standard deviation: 9.17) were included in this study. Over a span of 7 years, 2,527 cases of hearing impairment were reported, with an incidence rate of 18.6%. A higher degree of residential greenness was inversely associated with the risk of hearing impairment, showing a HR of 0.688 (95%CI: 0.659–0.719) for every 0.1 unit increment in NDVI. In contrast, a 10 µg/m³ elevation in PM_2.5 and PM₁₀ concentration was linked to a 67.6% (HR: 1.676; 95%CI: 1.625–1.729) and 30.4% (HR: 1.304; 95%CI: 1.284–1.324) increased risk of hearing impairment, respectively. The harmful effects of PM_2.5 and PM₁₀ were attenuated with higher levels of residential greenness. Furthermore, the mediation analysis revealed that PM_2.5 and PM₁₀ played a significant mediating role in the association between residential greenery exposure and hearing impairment, with mediation proportions of 47.91% for PM_2.5 and 52.83% for PM₁₀.

Conclusions

High residential greenness was associated with a reduced risk of hearing impairment, whereas exposure to PM_2.5 and PM₁₀ may increase the risk of hearing impairment. Additionally, residential greenness may modify the relationship between PM exposure and hearing impairment by reducing exposure to PM_2.5 and PM₁₀.