Long-Term Exposure to Non-Optimal Ambient Temperatures associated with Dialysis Incidence and Mortality in Advanced CKD Patients: A Population-Based Cohort Study in Taiwan

Background Chronic kidney disease (CKD) of unknown etiology, potentially related to heat stress, has been reported among agricultural workers in tropical low- and middle-income countries. While high-income countries have greater heat-adaptation capacity, evidence on CKD risks from heat exposure in warm high-income settings is limited. Moreover, the effects of prolonged exposure to non-optimal cold or heat on kidney health remain unclear. This study investigates the associations between long-term non-optimal daytime temperature exposure and the risks of dialysis progression and mortality in advanced CKD patients in Taiwan. Methods We conducted a nationwide retrospective cohort study to examine associations between long-term exposure to non-optimal daytime temperatures and risks of dialysis progression and mortality among patients with advanced CKD in Taiwan. Data from 86,928 advanced CKD patients enrolled between 2008 and 2021 were analyzed, with follow-up through December 31, 2022. Non-optimal temperature days were defined as mean daytime temperatures ≥ 30°C (hot) or ≤ 15°C (cold). Time-weighted percentages and mean temparatures for hot and cold days were calculated for each patient. Additonally, mean daytime temperature across all days during the follow-up period was also used as an exposure index. Cox proportional hazards models estimated hazard ratios (HRs) for dialysis progression and mortality per 1% increase in exposure. Cumulative incidence curves assessed outcome differences across exposure quartiles, and restricted cubic spline analyses evaluated dose–response relationships. Results Each 1% increase in time-weighted cold-day exposure was associated with a 14% higher risk of dialysis progression and a 9% higher risk of mortality. Conversely, a 1% increase in hot-day exposure was associated with 5% and 3% lower risks of dialysis progression and mortality, respectively. Spline analyses demonstrated a dose-dependent protective effect of higher mean temperatures. Higher mean daytime temperatures during follow-up were associated with lower risks of dialysis progression and mortality, whereas lower temperatures increased risks (P for both linearity and non-linearity < 0.001). Conclusions Long-term cold exposure increases dialysis and mortality risks in advanced CKD, whereas prolonged heat exposure may be protective for both outcomes, reflecting population-level heat adaptation. Our findings emphasize the need for climate-sensitive policies to mitigate the health impacts of non-optimal temperatures in vulnerable populations.