**Background:** Glaucoma is the leading cause of irreversible blindness worldwide, and while intraocular pressure (IOP) is the only modifiable risk factor, emerging evidence suggests ambient temperature may influence IOP and glaucoma risk. However, the impact of extreme temperature events—specifically heatwaves and cold spells—on glaucoma has been minimally studied. Given China's increasing exposure to climate change-related extreme weather, this study aimed to elucidate the association between heatwaves, cold spells, and glaucoma prevalence in a nationally representative rural Chinese population.
**Methods:** This cross-sectional analysis used data from the Rural Epidemiology for Glaucoma in China (REG-China) study, which recruited 52,041 participants from 10 provinces between June 2017 and October 2018. After exclusions, 33,699 participants aged ≥40 years were included. Glaucoma was diagnosed by ophthalmologists using the International Society of Geographical and Epidemiological Ophthalmology (ISGEO) criteria, categorized into primary open-angle glaucoma (POAG), primary angle-closure glaucoma (PACG), and other types. Temperature data were obtained from ERA5 reanalysis (2007–2016) at 0.25° resolution, and PM2.5 concentrations were estimated at 1 km resolution using satellite-based spatiotemporal models. Heatwaves were defined using 15 combinations of intensity (95th, 96th, 97th, 98th, or 99th percentile of mean temperature) and duration (≥2, ≥3, or ≥4 days). Cold spells were defined using 6 combinations of threshold percentiles (5th, 10th) and moving window durations (3, 5, or 9 days). Multivariable-adjusted logistic regression models were used, adjusting for age, sex, education, occupation, income, region, smoking, hypertension, diabetes, IOP, and PM2.5. Restricted cubic spline (RCS) models assessed dose-response relationships.
**Key Results:** Among 33,699 participants (mean age 62.27 years, 39.3% male), 707 (2.10%) had glaucoma, comprising 326 (0.97%) with PACG and 244 (0.72%) with POAG. The prevalence was 2.13% in men and 2.07% in women. For heatwaves, the odds ratio (OR) for glaucoma ranged from 1.014 (95% CI: 1.009–1.018) for HW01 (≥95th percentile, ≥2 days) to 1.090 (95% CI: 1.065–1.115) for HW15 (≥99th percentile, ≥4 days). For PACG, ORs ranged from 1.014 (95% CI: 1.008–1.021) for HW01 to 1.094 (95% CI: 1.055–1.135) for HW15. For POAG, ORs ranged from 1.018 (95% CI: 1.011–1.025) for HW01 to 1.096 (95% CI: 1.056–1.138) for HW15. For cold spells, ORs for glaucoma ranged from 1.004 (95% CI: 0.997–1.010) for CS01 (10th percentile, 9-day window) to 1.051 (95% CI: 1.026–1.078) for CS06 (5th percentile, 3-day window). Significant synergistic interactions were found between heatwaves and PM2.5 (OR > 1, P < 0.05). RCS analysis revealed nonlinear relationships (nonlinear P < 0.001) between heatwaves, cold spells, and temperature with IOP, central anterior chamber depth (CACD), and glaucoma risk. Temperature below 14°C was associated with shallower CACD. Subgroup analyses showed stronger effects in males (HW01 OR: 1.023, 95% CI: 1.016–1.029) versus females (OR: 1.008, 95% CI: 1.002–1.013), and in current smokers (HW01 OR: 1.022, 95% CI: 1.014–1.031) versus nonsmokers (OR: 1.009, 95% CI: 1.005–1.014). Participants with a family history of glaucoma were more sensitive to cold spells (CS01 OR: 1.116, 95% CI: 1.031–1.208) versus those without (OR: 1.002, 95% CI: 0.995–1.009; P < 0.05). Sensitivity analyses excluding cataract surgery patients, those with chronic diseases, and after adjusting for humidity and air pressure confirmed the robustness of the findings.
**Clinical Implications:** This is the first national study to demonstrate that both heatwaves and cold spells are independently associated with increased glaucoma prevalence in rural China, with risk escalating as extreme temperature events become more intense. The findings suggest that extreme temperature exposure may contribute to glaucoma through mechanisms beyond IOP elevation, potentially involving vasoconstriction, inflammatory responses, and thermoregulatory changes in ocular structures. The stronger effects observed in males and smokers highlight vulnerable subgroups that may benefit from targeted preventive measures. Clinicians should consider extreme temperature events as potential environmental risk factors for glaucoma, particularly in rural populations with limited access to climate-controlled environments. Public health strategies should incorporate climate adaptation measures into glaucoma prevention programs, especially as climate change increases the frequency and intensity of extreme weather events. However, the cross-sectional design limits causal inference, and prospective studies are needed to confirm these associations and elucidate underlying mechanisms.