Effects of cold and hot temperatures on the renal function of people with chronic disease.

Objectives: This study investigated the effects of hot and cold temperature on the renal function of people with chronic diseases, such as diabetes, hypertension, and chronic kidney disease, using large-scale clinical data.

Methods: We used retrospective cohort data from the Clinical Data Warehouse of the Seoul St Mary's Hospital, which contains clinical, diagnostic, laboratory, and other information about all patients who have visited the hospital since 1997. We obtained climate data from the Automated Synoptic Observing System of the Korea Meteorological Administration. The heat index was used as a measuring tool to evaluate heat exposure by indexing the actual heat that individuals feel according to temperature and humidity. The estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. To investigate changes in renal function trends with heat index, this study used generalized additive mixed models.

Results: Renal function decreased linearly with increasing heat index after approximately 25°C, which was considered the flexion point of temperature. A linear decrease in the eGFR was observed with the effects of 0 to 5 lag days. Although there was a correlation observed between the decrease in eGFR and temperatures below -10°C, the results did not indicate statistical significance.

Conclusions: The results of our study provide scientific evidence that high temperatures affect the renal function of people with chronic diseases. These results can help prevent heat-related morbidity by identifying those who are more likely to develop renal disease and experience worsening renal function.