2014—2017年兰州市气温与死亡人数关系的时间序列研究

Time-series study on association between temperature and mortality in Lanzhou from 2014 to 2017

[目的]探讨兰州市日均气温与居民死亡的关系,评估气温相关的非意外死亡、心血管疾病死亡及呼吸系统疾病死亡的风险。[方法]收集兰州市2014—2017年居民死亡资料以及同期气温数据和空气污染数据,采用分布滞后非线性模型,在调整长期趋势和季节效应、相对湿度及空气污染物影响的基础上研究气温对人群非意外死亡、心血管疾病死亡和呼吸系统疾病死亡的滞后效应和累积效应。选择滞后21 d作为最大滞后天数。在计算日均气温对死亡人数的影响时,用日均气温的P5(-4.2℃)和P95(25.5℃)相对于中位数(P50)计算的RR值代表各死因别的低温、高温效应,分别计算滞后0、0～3、0～7、0～14、0～21 d的累积效应值。[结果] 2014年1月1日至2017年12月31日,兰州市日均非意外死亡人数为39人,其中心血管疾病和呼吸系统疾病死亡分别为17人和5人。同期大气污染物PM10、SO2、NO2浓度日均值分别为123.54、21.91、49.88μg/m3。气温和相对湿度的日均值分别为11.35℃和50.76%。兰州市日均气温对非意外死亡、心血管疾病死亡和呼吸系统疾病死亡效应曲线均为J形。高温对非意外死亡和心血管疾病死亡的影响主要是急性短期效应,在29℃、滞后0 d(lag0)的效应RR值最大,RR及其95%CI分别为1.07(1.02～1.12)、1.09(1.02～1.18);呼吸系统疾病死亡对高温不敏感。低温存在较长的滞后效应,三种死亡均在-12℃,lag21时RR值最大,RR及其95%CI分别为1.36(1.26～1.45)、1.34(1.22～1.50)、1.45(1.22～1.72)。以年平均气温的中位数(P50,12.9℃)作为参照值,低温(P5,-4.2℃)对非意外死亡和心血管疾病死亡的累积效应均在lag0～21RR值最大,RR及其95%CI分别为1.15(1.07～1.23)和1.16(1.04～1.28);高温(P95,25.5℃)对非意外死亡的累积效应在lag0、lag0～3均有统计学意义,以lag0～3 RR值最大,RR及其95%CI为1.11(1.02～1.20)。[结论]高温和低温均是兰州市居民每日死亡的危险因素,存在滞后效应,且低温效应的滞后时间较长。

[Objective] To explore the relationship between daily average temperature and mortality in Lanzhou, and evaluate the temperature-related risk of non-accidental, cardiovascular, and respiratory mortalities.[Methods] Residents' death, temperature, and air pollution data in Lanzhou were collected from 2014 to 2017. A distributed lag nonlinear model was applied to explore the lag effect and cumulative effect of temperature on selected health outcomes with adjustments of long-term trends, seasonal effects, relative humidity, and air pollutants. We chose 21 d as the maximum lag time. RR values of P5 (-4.2℃) and P95 (-25.5℃) versus P50 of daily mean temperature were calculated to evaluate the cumulative effects of lag 0, 0-3, 0-7, 0-14, and 0-21 days, respectively.[Results] From January 1, 2014 to December 31, 2017, the daily average number of non-accidental deaths in Lanzhou was 39, of which 17 were caused by cardiovascular diseases and 5 by respiratory diseases, respectively. The daily mean concentrations of atmospheric pollutants PM10, SO2, and NO2 over the same period were 123.54, 21.91, and 49.88 μg/m3, respectively. The daily mean temperature and relative humidity were 11.35℃ and 50.76%, respectively. The effect of daily average temperature on the mortality of non-accidental, cardiovascular, or respiratory diseases each presented a J shaped curve. Heat mainly imposed acute short-term effect both on non-accidental and cardiovascular mortalities, and the maximum RRs of heat-related death occurred at 29℃ with 0 d lag, which were 1.07 (95%CI:1.02-1.12) and 1.09 (95%CI:1.02-1.18), respectively; respiratory mortality was not sensitive to heat. Unlike heat, cold temperature showed a long lag effect on mortality, and the maximum RRs of cold temperature on non-accidental, cardiovascular, and respiratory mortalities all occurred at -12℃ with 21 d lag, which were 1.36 (95%CI:1.26-1.45), 1.34 (95%CI:1.22-1.50), and 1.45 (95%CI:1.22-1.72), respectively. With the median annual mean temperature (P50, 12.9℃) as a reference value, the cumulative effects of low temperature (P5, -4.2℃) on non-accidental mortality and cardiovascular diseases mortality were both strongest at lag 0-21 d, and the RR values were 1.15 (95%CI:1.07-1.23) and 1.16 (95%CI:1.04-1.28), respectively; the cumulative effect of high temperature (P95, 25.5℃) on non-accidental mortality was significant at both lag 0 and lag 0-3 d, and was strongest at lag 0-3 d with the RR of 1.11 (95%CI:1.02-1.20).[Conclusion] High and low temperatures both increase the risk of selected mortalities with delayed effects in Lanzhou, and the effect of low temperature lasts longer than high temperature.