Effects Of Weather On Mortality In The Semi-Arid Climate Of Northwest Region

Objectives:To examine the effects of mean temperature (Tmean), diurnal temperature range (DTR) and relative humidity (RH) on different mortality categories in the semi-arid climate of Jingtai County, Gansu and to explore the more vulnerable populations to variations of weather and the sensitive atomosphere index to cause-specific mortality.Methods:(1) The daily data on meteorology from January1st1970to December31st2009were collected and then analysed the characteristics of climate change in recent40years and the distribution charactreistics of meteorology data from January1st2004to December31st2009by the descriptive statistics methods.(2) The linear regression was applied to investigate the trend of climate change in Jingtai. Descriptive statistics method was used to analyse the distribution charactreistics of death records of survenillance system from January I st2004to December31st2009.(3) The distibuted lag nonlinear model (DI.NM) combined with generalized additive model (GAM) was applied to assess the non-linear and delayed effects of Tmean, DTR and RH on non-external mortality (Dall), age-specific non-external mortality (0-64(D0-64),65-74(D65-74), and>75years (D75+)), gender-specific mortality (male (Dm) and female (Dr)) and cause-specific mortality (circulatory disease (Dc) and respiratory disease (Dr)).We used a natural cubic spline-natural cubic spline DLNM to assess the effects of extreme low (1st percentile of Tmean and RH) and high values of Tmean, DTR and RH (99th percentile of Tmean, DTR and RH)on different mortality categories. The effects of extreme low values of Tmean and RH were estimated by the cumulative relative risk (RR) of mortality associated with extreme low values relative to10th percentile of Tmean and RH. The effects of extreme high values of Tmean and RH were estimated by the cumulative RR of mortality associated with extreme high values relative to90th percentile of Tmean, DTR and RH during different delayed periods, respectively.We used a linear threshold-natural cubic spline DLNM to assess the effects of cold temperature below the cold threshold, hot temperature above the hot threshold, high DTR above the DTR threshold, low humidity below the dry threshold, and high humidity above the wet threshold. The effects were estimated by the percent changes of mortality associated with1℃ change of Tmean, DTR and1%change of RH, respectively.Results:(1) The warming rate of Tmean in Jingtai during1970-2009was0.59℃/10a. The rate of decreasing of RH was0.16℃/10a. There was no significant change of RH.(2) The first three death causes were circulatory disease and respiratory disease. The motality of male was higher than female. The mortality of people above75years old was higher than low age groups.(3) The effecs of Tmean on mortality follows.A U-shaped relationship was found between Tmean and mortality.The greatest cummlative RRs (95%CI) of Dall, D0-64and Dr associated with extreme low Tmea during the delayed period of the study were1.217(1.040,1.425),1.363(1.036,1.792) and1.296(1.027,1.635). Extreme low Tmean had no statistically significant effect on other mortality.The greatest cummlative RR (95%C1) of D。associated with extreme high Tmean during the delayed period of the study was1.138(1.003,1.291). Extreme high Tmean had no statistically significant effect on other mortality.Generally, the cold effects on all mortality types were delayed by4-5days and persisted for20-30days, while the hot effects were immediate and lasted for2days.For a1℃decrease below the cold threshold, the percent increases in Dall, D0-64. D-75-and Df were:1.995%(95%CI:0.520,3.492),5.368%(95%CI:1.359,9.536),2.224%(95%CI:0.100,4.392) and2.86I%(95%CI:0.677,5.091) for Lag0-30, respectively. For a1℃increase above the hot threshold, the percent increase in D。was3.008%(95%CI:0.495,5.583) for Lag0-1.(4) The effecs of DTR on mortality follows.A J-shaped relationship was found between DTR and mortality.The cummlative RR (95%CI) of D65-74associated with extreme high DTR was1.719(95CI:1.000,2.956) for Lag0-8.The effects of DTR on all mortality types were immediate and reached maxima at lags of0-2days. For a1℃increase above the DTR threshold, the percent increases in Dall, D75, and Df were1.637%(95%CI:0.075,3.223),4.029%(95%CI:0.492,7.692) and2.831%(95%CI:0.464,5.254).(5) The effecs of RH on mortality follows.A U-shaped relationship was found between RH and mortality.The RRs (95%CI)of D0-64associated with extreme low RH was1.171(95CI:1.010,1.358) for LagO. The RRs (95%CI) of D75+, Dc and Dr associated with extreme high RH were1.560(95C1:1.081,2.251),1.563(95C1:1.085,2.252) and1.819(95CI:1.045,3.166) for LagO.The dry and wet effects were immediate and reached maxima at a lag of0-1day.For a1%decrease below the dry threshold, the percent increases in Dall, D0-64, Dm and Dc were0.480%(95%CI:0.127,0.834),1.431%(95%CI:0.467,2.405),0.578%(95%CI:0.108,1.050) and0.695%(95%CI:0.207,1.186). For a1%increase above the wet threshold, the percent increases in Dall, D75+, Df, Dc and Dr were0.572%(95%CI:0.172,0.973),0.873%(95%CI:0.120,1.632),0.756%(95%CI:0.005,1.513),0.963%(95%CI:0.132,1.802) and3.983%(95%CI:0.203,7.905).Conclusions:(1) The average temperature in Jingtai had been increasing in recent40years. The DTR had been decreasing. The humidity had no obvious change.(2) In Jingtai, extreme and hot cold temperature temperature, low and high humidity and high DTR increasd the risk of mortality to some degree.(3) The effects of hot, dry, wet and high DTR were immediate. The cold effect was delayed for4-5days and lasted for longer days.(4) Women and populations of0-64years and above75years old were vulnerable to cold effect. Populations of more than64years were vulnerable to high DTR. Populations of0-64years old were vulnerable to dry effect. Populations above75years old and women were vulnerable to wet effect.(5) The circulatory disease mortality was sensitive to hot temperature, low and high humidity, and respiratory disease mortality was sensitive to high humidity. The non-accident mortality was sensitive to cold temperature.