title: Added effect of heat wave on mortality in Seoul, Korea.
abstract: A heat wave could increase mortality owing to high temperature. However, little is known about the added (duration) effect of heat wave from the prolonged period of high temperature on mortality and different effect sizes depending on the definition of heat waves and models. A distributed lag non-linear model with a quasi-Poisson distribution was used to evaluate the added effect of heat wave on mortality after adjusting for long-term and intra-seasonal trends and apparent temperature. We evaluated the cumulative relative risk of the added wave effect on mortality on lag days 0-30. The models were constructed using nine definitions of heat wave and two relationships (cubic spline and linear threshold model) between temperature and mortality to leave out the high temperature effect. Further, we performed sensitivity analysis to evaluate the changes in the effect of heat wave on mortality according to the different degrees of freedom for time trend and cubic spline of temperature. We found that heat wave had the added effect from the prolonged period of high temperature on mortality and it was considerable in the aspect of cumulative risk because of the lagged influence. When heat wave was defined with a threshold of 98th percentile temperature and ≥2, 3, and 4 consecutive days, mortality increased by 14.8 % (7.5-22.6, 95 % confidence interval (CI)), 18.1 % (10.8-26.0, 95 % CI), 18.1 % (10.7-25.9, 95 % CI), respectively, in cubic spline model. When it came to the definitions of 90th and 95th percentile, the risk increase in mortality declined to 3.7-5.8 % and 8.6-11.3 %, respectively. This effect was robust to the flexibility of the model for temperature and time trend, while the definitions of a heat wave were critical in estimating its relationship with mortality. This finding could help deepen our understanding and quantifying of the relationship between heat wave and mortality and select an appropriate definition of heat wave and temperature model in the future studies.
authors.affiliation: Department of Social and Preventive Medicine, Inha University School of Medicine, 27 Inhang-Ro, Jung Gu, Incheon, Republic of Korea.
authors.forename: Won Kyung
authors.initials: WK
authors.lastname: Lee
authors.affiliation: Department of Preventive Medicine, School of Medicine, Ewha Womans University, 1071, Anyangcheon-ro, Yangcheon-ku, Seoul, 158-710, Republic of Korea.
authors.forename: Hye Ah
authors.initials: HA
authors.lastname: Lee
authors.affiliation: Institute of Environmental Medicine, Seoul National University of Medical Research Center, Seoul National University, Seoul, Republic of Korea.|Environmental Health Center, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Youn Hee
authors.initials: YH
authors.lastname: Lim
authors.affiliation: Department of Preventive Medicine, School of Medicine, Ewha Womans University, 1071, Anyangcheon-ro, Yangcheon-ku, Seoul, 158-710, Republic of Korea. hpark@ewha.ac.kr.
authors.forename: Hyesook
authors.initials: H
authors.lastname: Park
mesh_terms: D002318:Cardiovascular Diseases / Q000401:mortality; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D009026:Mortality; D017711:Nonlinear Dynamics; D012140:Respiratory Tract Diseases / Q000401:mortality; D012306:Risk; D066106:Seoul
keywords: Heat wave; Mortality; Temperature; Weather