Extreme Compound Cold in China and Its Impact on Mortality Risk and Burden of CKD: A Time-Stratified Case-Crossover Study

Background: Cold weather is a major health threat. CKD patients, being weather-sensitive, are particularly vulnerable. Existing studies link cold to CKD complications remains limited. Understanding this relationship is crucial for reducing CKD deaths. Methods: Using CKD mortality data, air pollutants, and meteorological data from six provinces/autonomous regions (2013–2018), we analyzed cold exposure–CKD mortality associations via conditional logistic regression (time-stratified case-crossover design). Distributed lag nonlinear models (DLNM) assessed lag effects of different cold types. Stratified analyses examined associations by sex, age, and regional cold traits (intensity/persistence), with attributable fractions (AF) quantifying cold-related disease burden and CKD vulnerability. An interaction index evaluated additive effects of daytime/nighttime cold on CKD mortality. Results: Wintertime cold exposure significantly increased CKD mortality risk, with compound cold events showing the strongest association (RR=1.17, 95%CI:1.04-1.31) compared to daily (RR=1.10) or nocturnal cold (RR=1.13). The effect peaked on the first day (ER%=4.19 for compound cold), with cold intensity being more impactful than duration. Vulnerable subgroups included males (RR=1.21, AF%=17.47), elderly >65 years (RR=1.18, AF%=15.43), and urban residents (RR=1.45, AF%=31.2), while rural populations and younger patients were more sensitive to cold intensity. No additive interaction was found between daytime and nighttime cold exposures. Conclusion: Cold exposure significantly increases CKD mortality risk, with compound cold events posing the greatest threat. Effects are immediate (peak at Day 1) and driven more by cold intensity than duration. Vulnerable subgroups include males, elderly (>65 years), and urban populations. Public health strategies should prioritize these groups during cold waves.Relationship between daily temperature and exposure response to CKD mortality