Modelling the excess mortality associated with heat waves in Hong Kong: 2014-2023

Background Heat waves have become increasingly frequent, and prior studies have linked them to elevated mortality risks in Hong Kong. However, estimates of the total excess mortality burden attributable to heat waves in Hong Kong remain limited. This study aimed to estimate excess mortality associated with heat waves in Hong Kong from 2014 to 2023. Methods and findings We obtained daily age- and sex-specific mortality rates and population data from the Hong Kong Life Tables and the Census and Statistics Department. Historical temperature data were sourced from the Hong Kong Observatory, and relative risk estimates were derived from published local studies. Using a Monte Carlo approach, we estimated heat-attributable deaths under multiple heat wave definitions and calculated both cumulative excess death counts and age-standardized annual excess death rates per 100,000 population. From 2014 to 2023, the estimated cumulative number of excess deaths attributable to heat exposure in Hong Kong ranged from 1,455 (95% CI: 1,098–1,812) to 3,238 (95% CI: 3,234–3,242), depending on the heat wave definition applied. In 2023, the annualized excess death rate ranged from 2.95 per 100,000 population (95% CI: 2.41–3.50) to 5.09 per 100,000 population (95% CI: 5.07–5.12). Variations in heat wave frequency and intensity were associated with corresponding fluctuations in mortality burden. Excess mortality was disproportionately higher among males and adults aged 65 years or above, indicating greater vulnerability in these groups. Conclusions Between 2014 and 2023, extreme heat was associated with an estimated 1,455–3,238 excess deaths in Hong Kong. If considered as an independent health condition, the mortality burden attributable to extreme heat would rank among the leading causes of death in Hong Kong, with annual mortality rates comparable to those of diabetes. Older adults bore a substantially greater mortality burden than younger and working-age populations. These findings underscore the importance of evidence-based heat-health policies and targeted interventions to protect vulnerable populations, particularly older adults, during periods of extreme heat.