Diurnal Temperature Range and Emergency Department Visits for Asthma in Korea 6 Cities

[Purpose]  Asthma is a major public health problem, and many studies have shown that diurnal temperature change (DTR) is associated with asthma mortality and emergency department(ED) visits as asthma morbidity. These studies represented that DTR and asthma ED visit showed non-linear relationship and had lagged effect up to 7-14 days, however only few study considered these two characteristics simultaneously. This study aim to find an association between DTR and asthma ED visit including non-linear and lagged effects.

[Method] ED data of 6 Korean cities (Seoul, Busan, Daejeon, Daegu, Gwangju, and Incheon) were collected from January 1, 2008 to December 31, 2010, through the National Emergency Department Information System (NEDIS) for the National Emergency Medical Center. We applied 2 stage distributed lag non-linear model (DLNM) with 10 lag days and an allowance of over-dispersion adjusting for meteorological conditions and time trend.

[Result] From 2 stage analysis, we found DTR was adversely associated with asthma-related ED visits in Korea and as DTR increased, so did the risk of ED visit. The relative risks of asthma-related ED visit were estimated with Mid-high (80^th percentile versus minimum mortality DTR), High (90^th percentile versus minimum mortality DTR) and Extreme high (99^th percentile versus minimum mortality DTR). Relative risks were 1.032[95% CI, 0.82, 1.29] at Mid-high condition, 1.132[0.88, 1.46], at High and 1.543[0.69, 3.46] at Extreme high.

[Conclusion] We found that DTR had adverse effect to ED visits in Korea. And effect of DTR showed non-linear relationship and was significant up to 10 days. Therefore as DTR increases, the more vulnerable people and public health authorities should pay special attention to an acute exacerbation of asthma.