Summer temperature and emergency room visits due to urinary tract infection in South Korea: a national time-stratified case-crossover study

Abstract Background Although urinary tract infection (UTI) is a common and severe public health concern, and there are clear biological mechanisms between UTI and hot temperatures, few studies have addressed the association between hot temperatures and UTI. Methods We designed a time-stratified case-crossover study using a population-representative sample cohort based on the national health insurance system (NHIS) in South Korea. We obtained all NHIS-based hospital admissions through the emergency room (ER) due to UTI (using a primary diagnostic code) from 2006 to 2019. We assigned satellite-based reanalyzed daily summer (June to September) average temperatures as exposures, based on residential districts of beneficiaries (248 districts in South Korea). The conditional logistic regression was performed to evaluate the association between summer temperature and UTI outcome. Results Among 4,450 ER visits due to UTI were observed during the summer between 2006 and 2019 among 1,131,714 NHIS beneficiaries. For 20% increase in summer temperature (moving average of 0–2 lag days), the odd ratio (OR) was 1.05 (95% CI: 1.02, 1.09) in the total population, and the association was more prominent in the elderly (people aged 65y or older; OR: 1.09, 95% CI: 1.04, 1.15), females (OR: 1.10, 95% CI: 1.04, 1.17), and people with diabetes history (OR: 1.12, 95% CI: 1.05, 1.19). The effect modification by household income was different in the total and elderly populations. Furthermore, the association between summer temperature and UTI increased during the study period in the total population. Conclusions Higher summer temperatures were associated with an increased risk of ER admissions for UTI. The results are consistent with the hypothesis that higher summer temperatures increase the risk of severe UTIs.