High Heat Exposure and Medical Utilization among the CKD Population

Key Points Exposure to days with higher heat indices was associated with increases in weekly utilization for a population with CKD. Higher heat indices were associated with a larger increase in kidney-related visits than all-cause utilization. Higher heat indices were associated with larger effects on kidney-related emergency department use for those least likely to have air conditioning. Background Extreme heat events have lengthened, become more frequent, and increased in intensity over the past few decades, and this trend is expected to continue. Extreme heat events have been shown to be associated with increased mortality and emergency department (ED) visits. Methods We investigated the relationship between temperature and healthcare utilization among patients with CKD. We used panel regression models with individual and year fixed effects to evaluate how exposure to different levels of temperature (measured by heat index) was associated with changes in weekly healthcare utilization from October 1, 2015, to March 31, 2023. Data were derived from medical claims data, Parameter-Elevation Regressions on Independent Slopes Model climate data, and the Census block group of each individual. The study population was comprised of 916,886 individuals with commercial or Medicare insurance who had been diagnosed with CKD stage G3, G4, or G5. CKD was defined using diagnosis codes in medical claims and eGFR laboratory results. Exposure was the number of days in a week with a daily heat index in 5.6-degree Celsius bins. Results We found that exposure to a higher heat index bin, 32.2°C–37.8°C compared with 15.6°C–21.1°C, was associated with an increase in weekly ED utilization (0.55%; 95% confidence interval [CI], 0.42% to 0.68%; P < 0.001), with larger percent increases for ED visits with a heat-related primary diagnosis code (2.07%; 95% CI, 1.63% to 2.51%; P < 0.001) or a kidney-related primary diagnosis code (1.37%; 95% CI, 0.56% to 2.17%; P < 0.001). ED visits with a primary diagnosis code related to kidney disease were associated with a larger effect among those least likely to have access to air conditioning (2.48%; 95% CI, 0.84% to 4.13%; P < 0.01). Smaller, statistically significant results were observed comparing heat indexes of 26.7°C–32.2°C to 15.6°C–21.1°C. Conclusions Exposure to heat indexes above 32.2°C was associated with greater weekly ED utilization and ED utilization with heat-related or kidney-related primary diagnosis codes.