Impact of heat on respiratory health: Age- and sex-specific risks in a nationwide Korean study (2014-2019).

Respiratory diseases pose a major global public health challenge. With climate change contributing to more frequent and intense heat events, understanding the effects of high temperatures on respiratory health is increasingly critical. However, existing evidence remains inconsistent. A nationwide time-series study was conducted to evaluate the association between daily maximum temperatures and emergency department (ED) visits for cause-specific respiratory diseases across 16 regions in South Korea during the warm season (April-September) from 2014 to 2019. Generalized additive models with quasi-Poisson regressions were applied, adjusting for long-term trends, humidity, day of the week, and air pollutants. Subgroup analyses were performed by age and sex. Each 1 °C increase in maximum temperature was associated with a significant increase in ED visits for total respiratory diseases (relative risk [RR] = 1.008; 95% confidence interval [CI]: 1.006-1.009). Stronger associations were observed for pneumonia (RR = 1.014; 95% CI: 1.012-1.016), COPD (RR = 1.010; 95% CI: 1.007-1.012), asthma (RR = 1.009; 95% CI: 1.007-1.011), and upper respiratory infections (RR = 1.005; 95% CI: 1.003-1.007). Males, children (< 15 years), and the elderly (≥ 65 years) were particularly vulnerable. High ambient temperatures are significantly associated with increased ED visits for respiratory diseases. These findings provide important evidence to guide governmental decision-making in developing heatwave preparedness policies, including targeted interventions, early warning systems, and healthcare resource planning for vulnerable populations.