Ambient temperature-related attributable risk for emergency asthma hospitalizations and length of stay in Hong Kong

We aimed to examine the association of ambient temperature with asthma exacerbations and assess the temperature-attributable disease burden changes. Daily count of asthma emergency hospitalizations and corresponding length of hospital stay, daily mean temperature, relative humidity, and air pollution concentrations from 2004 to 2019 in Hong Kong were collected. Time-series quasi-Poisson model integrated with the distributed-lag-nonlinear model was used to examine the relationships of temperature with asthma hospitalizations and length of stay. Measures of the risk attributable to nonoptimal temperature were calculated to summarize the disease burden and hospital utilization for periods of 2004–2011 and 2012–2019, respectively, and compared the temporal changes. Significantly higher risks at cold/cool temperatures for both admission counts and bed-days were found. Around 19.7 % (95 % CI: 14.1–24.3 %) of hospitalization counts and 22.6 % (95 % CI: 15.5–28.4 %) of bed-days were attributed to ambient temperature, which mainly occurred on cold and cool days. Compared with the early period of 2004–2011, the cold temperature-related attributable fraction in 2012–2019 decreased from 11.0 % to 8.9 % (p = 0.005) for admission counts but increased from 10.8 % to 12.6 % (p = 0.003) for bed-days. Hospital utilization and expenditure due to the longer hospital stays during cold days would play an adverse role in the healthcare system.