Emergency Cardiovascular Hospitalization Risk Attributable to Cold Temperatures in Hong Kong

Associations between ambient temperature and cardiovascular morbidity have been well studied worldwide; however, few studies determined the cardiovascular disease burden attributable to temperature. We aimed to assess the risk attributed to temperature based on the exposure-lag-response relationship between temperature and circulatory diseases.

We collected daily time series data of emergency hospital admissions, mean temperature, and air pollution concentrations from January 2005 to December 2012 in Hong Kong. The association with temperature was modeled using a distributed lag nonlinear model integrated in quasi-Poisson regression. The cumulated effects of cold/hot temperature were abstracted. Attributable risk measures because of below optimal temperature (OT) were calculated to summarize the disease burden, and further separated into contributions from moderate and extreme cold temperatures. We observed significant nonlinear and delayed cold effect but no apparent hot effect lasting for 3 weeks on emergency circulatory hospitalizations. Compared with the identified OT at 23.0°C, the cumulative relative risk during 0 to 21 lag days was 1.69 (95% confidence interval, 1.56-1.82) for extreme cold (first percentile) and 1.22 (95% confidence interval, 1.15-1.29) for moderate cold temperature (10th percentile). Cold temperatures were responsible for temperature-related circulatory emergency hospitalizations, with attributable fraction of 6.33% for moderate cold and 0.82% for extreme cold while inducing 33 030 and 4257 cases, respectively. Several specific causes of cardiovascular diseases showed higher vulnerability.

Moderate cold weather was responsible for a considerable attributable risk for cardiovascular diseases. The temperature-related hospitalizations risk found in this study may provide evidence for guiding the public health policies and preventions for cardiovascular diseases.