Association between dry eye disease and temperature is modified by residential greenness: case-crossover study in Beijing, China

Dry eye disease (DED) is one of the most prevalent eye conditions globally. While the harmful effects of air pollution on DED are well-documented, the role of temperature—an important factor linked to climate change—remains less understood. Green spaces have been identified as a potential way to reduce health risks from climate change, yet few studies have examined their combined influence on DED. A time-stratified case-crossover study was conducted using data of 71,069 first-time outpatient visits for DED at Peking University People’s Hospital in Beijing, from January 2012, to October 2022. We analyzed the linear association between daily average temperature and DED using a conditional logistic regression model and developed a non-linear exposure-response function linking DED to temperature exposure. Participants’ normalized difference vegetation index (NDVI) was estimated and used to represent greenness exposure, and a novel varying-coefficient model was used to explore the non-linear modifying effects of greenness exposure on the temperature-DED association. Our findings indicate a positive association between temperature and DED, with a 0.8% excess risk (95% confidence interval [CI] 0.4%, 1.2%) for per 1 °C increment in temperature. Residential greenness appeared to have a protective effect against temperature-related DED. Participants living in areas with the lowest NDVI were the most vulnerable, experiencing a 1.8% excess risk (95% CI 1.1%, 2.5%) of temperature-related DED, while no significant temperature effect was observed in areas with high NDVI. The varying-coefficient model suggests a sublinear curve for the protective modifying effect of greenness on the population vulnerability to temperature. High temperatures were linked to an increased risk of DED, while residential greenness provided a protective buffer against temperature-related risks. These results highlight the need for urban planning and public health strategies that incorporate green spaces to help mitigate the growing burden of DED in the context of climate change.