Diurnal Temperature Range and Cause-specific Cardiovascular Hospital Admission in Seoul, Korea—Time-series Analysis and Temperature-Matched Case-crossover Design

Abstract

O-29A1-3 Background/Aims: Rapid temperature change within a day may increase blood pressure, clot, or cardiovascular work load. Hence, diurnal temperature range (DTR) may cause higher risk of cardiovascular disease (CVD) for population vulnerable to thermal stress. In this study, we hypothesized an increase of DTR which was associated with cardiovascular-related hospital admission in Seoul, South Korea. Methods: Data of daily hospital admission counts of 6 cause-specific CVD diseases in Seoul were collected from Korea National Health Insurance Corporation during 2003–2006. CVD diseases were arrhythmia, cardiac disease, cardiac failure, ischemic heart disease, myocardial infarction, and stroke. Results of time-series analysis and temperature-matched case-crossover design were compared. Associations in time-series analysis were evaluated using generalized linear model (glm) adjusted for confounding factors. In temperature-matched case-crossover design, control days were selected with temperature within ±1°C. Models included the first day of the month, day of the week, mean pressure, PM10, influenza, and relative humidity. Cause-specific effect of DTR was presented in percent change of risk. Results: Case-crossover design showed similar or greater effect than time-series analysis did. For time-series analysis, hospital admission risk was increased by 0.4%, 0.5%, 0.7%, and 1.4% for cardiac disease, stroke, myocardial infarction, and cardiac failure, respectively, with an increase of 1°C DTR. Significant risk of CVD-related hospital admission occurred after 5–8 days of higher DTR, depending on the symptoms. Conclusion: Case-crossover design and time-series analysis showed that DTR was a risk factor for cause-specific CVD hospital admission in Seoul.