Combined Effects of Long‐Term Sulfur Dioxide Exposure and Environmental Heat Stress on the Risk of Kidney Stone Disease

OBJECTIVES: Kidney stone disease is influenced by environmental, metabolic, and climatic factors. Although sulfur dioxide and environmental heat stress have each been associated with renal dysfunction, their combined long-term effects on kidney stone development remain unclear. This study examined whether chronic exposure to ambient sulfur dioxide and environmental heat stress was associated with incident kidney stone disease. METHODS: A total of 20 670 participants from the Taiwan Biobank who were free of kidney stones at baseline were analyzed and followed for a mean of 42.8 months. Long-term exposures to sulfur dioxide and environmental heat stress were estimated using validated Geo-artificial intelligence-based spatiotemporal models to derive 10-year moving averages at 1 km spatial resolution. Incident kidney stone disease was identified through standardized follow-up questionnaires. Cox proportional hazards models evaluated the independent and joint associations after adjustment for demographic, lifestyle, and metabolic covariates. RESULTS: During follow-up, 511 participants developed incident kidney stones. Higher sulfur dioxide exposure demonstrated a dose-response association with kidney stone risk, with adjusted hazard ratios of 1.29, 1.75, and 1.77 across increasing exposure quartiles compared with the lowest quartile. Elevated environmental heat stress was also associated with an increased kidney stone risk, with an adjusted hazard ratio of 1.56. Stratified analyses indicated that environmental heat stress further amplified kidney stone risk among individuals with lower sulfur dioxide exposure. CONCLUSIONS: Long-term exposure to sulfur dioxide and environmental heat stress was independently associated with increased kidney stone risk. Their combined association suggests that heat stress may modify the relationship between air pollution and kidney stone formation.