Both low and high temperature may increase the risk of stroke mortality.
OBJECTIVE
To examine temperature in relation to stroke mortality in a multicity time series study in China.


METHODS
We obtained data on daily temperature and mortality from 8 large cities in China. We used quasi-Poisson generalized additive models and distributed lag nonlinear models to estimate the accumulative effects of temperature on stroke mortality across multiple days, adjusting for long-term and seasonal trends, day of the week, air pollution, and relative humidity. We applied the Bayesian hierarchical model to pool city-specific effect estimates.


RESULTS
Both cold and hot temperatures were associated with increased risk of stroke mortality. The potential effect of cold temperature might last more than 2 weeks. The pooled relative risks of extreme cold (first percentile of temperature) and cold (10th percentile of temperature) temperatures over lags 0-14 days were 1.39 (95% posterior intervals [PI] 1.18-1.64) and 1.11 (95% PI 1.06-1.17), compared with the 25th percentile of temperature. In contrast, the effect of hot temperature was more immediate. The relative risks of stroke mortality over lags 0-3 days were 1.06 (95% PI 1.02-1.10) for extreme hot temperature (99th percentile of temperature) and 1.14 (95% PI 1.05-1.24) for hot temperature (90th percentile of temperature), compared with the 75th percentile of temperature.


CONCLUSIONS
This study showed that both cold and hot temperatures were associated with increased risk of stroke mortality in China. Our findings may have important implications for stroke prevention in China.
From the School of Public Health, Key Lab of Public Health Safety of the Ministry of Education (R.C., C.W., X.M., H.K.), Research Institute for the Changing Global Environment and Fudan Tyndall Centre (R.C., C.W., X.M., H.K.), and Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP) (R.C., C.W., X.M., H.K.), Fudan University, Shanghai, China; Epidemiology Branch (H.C.), National Institute of Environmental Health Science, National Institutes of Health, Research Triangle Park, NC; and Department of Community Medicine (T.Q.T., C.-M.W.), School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region, China.
Renjie
R
Chen
Cuicui
C
Wang
Xia
X
Meng
Honglei
H
Chen
Thuan Quoc
TQ
Thach
Chit-Ming
CM
Wong
Haidong
H
Kan
D000393:Air Pollutants / Q000009:adverse effects; D002681:China; D003080:Cold Temperature / Q000009:adverse effects*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D012621:Seasons; D020521:Stroke / Q000209:etiology / Q000401:mortality*; D013997:Time Factors
D000393:Air Pollutants