Extreme Heat Stress and Unplanned Hospital Admissions.

OBJECTIVES The burden and health impact of heat stress on child hospitalization is limited. This study aims to investigate associations between extreme heat stress exposure based on a Universal Thermal Climate Index (UTCI), emergency department (ED) visits, and ED visits that translate into unplanned hospital admissions. METHODS This population-based case-crossover study included all ED visits and unplanned hospital admissions among children and adolescents aged 0 to 18 years from New South Wales, Australia, from July 2001 to June 2020. Heat stress was measured by heatwave days defined as 2 consecutive days or more with daily maximum UTCI in the 95th percentile or higher. Distributed lag nonlinear regression models with a quasi-Poisson distribution were applied, and the relative risks from the models were presented. RESULTS Totals of 8 240 170 ED visits and 1 427 736 unplanned hospital admissions were recorded. Compared with nonheatwave days, heatwave days were associated with an increased risk of ED visits and hospital admissions due to infectious diseases and infectious enteritis by 5% to 17% and heat-related illness by 78% to 104%. Findings were consistent for subgroup analyses. Children aged younger than 1 year and those from the most disadvantaged areas were more vulnerable to heat-related illness on heatwave days. Effects on hospitalization were attenuated using ambient temperature only. CONCLUSIONS This study provides evidence of the effectiveness of UTCI to more completely demonstrate the harmful impact of extreme heat stress on increased infection and heat-related hospitalizations among children, which were not fully captured by using ambient temperature alone. Findings can inform targeted area-based strategies, particularly among vulnerable groups to mitigate the effects of extreme heat events.