Estimation of Short-Term Effects of Air Pollution on Stroke Hospital Admissions in Wuhan, China

BACKGROUND AND OBJECTIVE: High concentrations of air pollutants have been linked to increased incidence of stroke in North America and Europe but not yet assessed in mainland China. The aim of this study is to evaluate the association between stroke hospitalization and short-term elevation of air pollutants in Wuhan, China. METHODS: Daily mean NO(2), SO(2) and PM(10) levels, temperature and humidity were obtained from 2006 through 2008. Data on stroke hospitalizations (ICD 10: I60–I69) at four hospitals in Wuhan were obtained for the same period. A time-stratified case-crossover design was performed by season (April-September and October-March) to assess effects of pollutants on stroke hospital admissions. RESULTS: Pollution levels were higher in October-March with averages of 136.1 µg/m(3) for PM(10), 63.6 µg/m(3) for NO(2) and 71.0 µg/m(3) for SO(2) than in April-September when averages were 102.0 µg/m(3), 41.7 µg/m(3) and 41.7 µg/m(3), respectively (p<.001). During the cold season, every 10 µg/m(3) increase in NO(2) was associated with a 2.9% (95%C.I. 1.2%–4.6%) increase in stroke admissions on the same day. Every 10 ug/m(3) increase in PM(10) daily concentration was significantly associated with an approximate 1% (95% C.I. 0.1%–1.4%) increase in stroke hospitalization. A two-pollutant model indicated that NO(2) was associated with stroke admissions when controlling for PM(10). During the warm season, no significant associations were noted for any of the pollutants. CONCLUSIONS: Exposure to NO(2) is significantly associated with stroke hospitalizations during the cold season in Wuhan, China when pollution levels are 50% greater than in the warm season. Larger and multi-center studies in Chinese cities are warranted to validate our findings.