Increasing residential greenness attenuates the hazard of ultraviolet radiation on age-related macular degeneration in the elderly: A nationwide study in China

Abstract

Background

Exposure to ultraviolet (UV) radiation may increase the risk of age-related macular degeneration (AMD), the leading cause of blindness in the elderly. However, prevention measures of UV radiation at population-level remain lacking, exacerbating the health inequity. Given the protective effect of residential greenness on human health, we aim to identify the impact of greenness on the UV-AMD association.

Methods

We used data from 19,832 participants in a national cohort in China conducted from 2018 to 2023. Satellite-based models and ophthalmological fundus images were used to evaluate the exposures (UV radiation and residential greenness) and outcome (incident AMD), respectively. The effects of UV radiation, residential greenness, and their interplay on incident AMD were furtherly estimated through multiple Cox proportional hazard models.

Results

A total of 3800 incident AMD cases were diagnosed during follow-up. Higher UV radiation elevated the hazard of incident AMD, while excessive greenness showed a significant protective effect, with hazard ratios of 1.35 (1.29, 1.41) and 0.90 (0.86, 0.94) for per tertile increment, respectively. These relationships remained consistent in two-exposure models, and a significant modification effect of greenness on the UV-AMD association was observed. Notably, when the residential greenness over 0.4, the hazard of UV on incident AMD became non-significant. This greenness threshold remained consistent across rural-urban and south-north subgroups.

Conclusion

Maintaining the residential greenness above 0.4, as a low-cost measure at population-level, could mitigate the UV-AMD association and facilitate the health equity in China, regardless of the regions.