Association of dust events with daily respiratory hospitalization: a time series approach (1995～2003 )
沙尘天气对呼吸系统疾病日入院人数影响的时间序列研究（1995～2003年）

To investigate the association between dust events, especially dust storms, and daily respiratory hospitalization and how the association(RR+)was distributed across various lags, six good-sized hospitals in Wuwei city of Gansu province, China, were selected. During the period from March 1~ st to May 31~ st in every year (from 1995 to 2003) when dust events occurred frequently annually, an investigation about daily respiratory hospitalization was conducted. After controlling long time trend, calendar effect and other meteorological confounding factors, we fit a semi-parametric generalized additive model (GAM) in each year (from 1995 to 2003) to allow for year-specific differences, then combined the calculated year-specific relative risks (RRs) by using fixed effect model of meta-analysis and the combination effect size of year-specific results (RR+) were obtained. Using these models that considered simultaneously the effect of dust events up to 7 days, The distributions of RR+ across lags of dust events were found. Our results show that (1) for dust storms, there were 3, 4, 5-day delayed effects of dust storms, their RR+ were 1.40 (95%CI 1.06~1.86), 1.34 (95%CI 1.01~1.77) and 1.73 (95%CI 1.35~2.23), respectively; (2) There was 6-day delayed effect of blowing dust (RR+=1.14(95%CI 1.01~1.30); (3) Similarly, the 6-day delayed effect of floating dust (RR+=1.12(95%CI 1.00~1.25) also was found; (4) According to the distribution of RR+ across various lags, the damaging effects of dust events on population health were divided into as initial-delayed effect, medium term- delayed effect and last-delayed effect. It might be due to different sensitives and responses of populations with the different damaging effects on dust events and different toxicological roles of various harmful factors in dust events; (5) The dominant respiratory diseases induced and aggravated by dust events included pneumonia, influenza and acute or chronic bronchitis and so on. These results indicated that there are the associations between dust events, especially dust storms, and daily respiratory hospitalization, and the influences of dust events on the hospitalization were delayed effects;The effect of dust storms was stronger than the effect of blowing dust or floating dust.