Investigating wet-bulb globe temperature on heat-related illness in general population for alerting heat exposure: A time-stratified case-crossover study

Assessing the effects of heat stress on heat-related illnesses and developing a heat alter system accordingly is an adaptive strategy to address global warming. The wet-bulb globe temperature (WBGT) effectively quantifies the heat stress on the human body, providing a more comprehensive measure than ambient temperature. However, few studies have assessed the association between WBGT and heat-related illnesses in the general population. We developed and validated a WBGT estimation model for the general population by incorporating in-situ measurements. A time-stratified case-crossover study was conducted to evaluate the effects of WBGT on heat-related illnesses. A total of 34,973 cases that occurred in Taiwan during 2004–2020 were retrieved from the National Health Insurance Research Database. Conditional logistic regression analysis was used to estimate effects as odds ratios (OR) with their 95 % confidence intervals (CI). We identified a significant association between WBGT and heat-related illnesses (OR = 1.414, 95 % CI: 1.399–1.428 per 1.0 °C increase). Although the risk of heat-related illnesses was the highest in summer, it remained significant in fall and spring, during temperature transitions. Additionally, males and the working-age population had a higher risk of emergency department visits. The WBGT ranks for alerting heat stress were categorized into “caution” (21.0–27.0 °C), “warning” (27.0–29.0 °C), “severe warning” (29.0–31.4 °C), and “danger” (> 31.4 °C). This study extends the conventional use of WBGT in occupational management to include instruments for public health communication. The described WBGT rankings can be used to validate current heat alert systems for preventing heat-related illnesses. • An new WBGT estimation model has been developed for general population. • The lagged effects of WBGT on heat-related illness were within four to five days. • The exposure-response relationship was linear and risk of heat stress significantly increased at WBGT of above 27.0 °C. • Male and working age populations are prone to influence by heat. • WBGT categories are caution (21.0–27.0 °C), warning (27.0–29.0 °C), severe warning (29.0–31.4 °C), and danger (> 31.4 °C).