Ballester F, Corella D, Pérez-Hoyos S, Sáez M, Hervás A
Department of Epidemiology and Statistics, Institut Valencià d'Estudis en Salut Pública (IVESP), Spain.
Int J Epidemiol. 1997 Jun;26(3):551-61. doi: 10.1093/ije/26.3.551.
Increased mortality is associated with both very low and very high ambient temperatures. This study assesses the relationship between daily numbers of deaths and variations in ambient temperature within the city of Valencia.
The daily number of deaths from all causes (total deaths and only those occurring in people aged over 70), as well as those deaths from specific causes (e.g. cardiovascular and respiratory diseases, malignant tumours and all causes except external ones) occurring within the city of Valencia were related to the average daily temperature using autoregressive Poisson regression controlling for seasonality, day of the week, holidays, air pollution, influenza incidence, and humidity. Temperature was measured within the regression model as two complementary variables: 'Heat' and 'Cold'; also taken into account were their delayed effects up to 2 weeks after measurement.
Graphical analysis revealed a relationship between temperature and mortality according to the time of year. For the cooler months (November-April), the temperature at which mortality was lowest was the 'minimum' (i.e. around 15 degrees C), while for the warmer months (May-October), it occurred at around 24 degrees C. Because of this, a stratified analysis was undertaken with different values for the 'Heat' and 'Cold' variables according to which of the two seasons was involved. During the colder months of the year, higher temperatures tended to exert a rapid influence on mortality and the lower temperatures a more delayed relation. During the hot season it is the heat variable which more clearly manifests an effect, and this is prolonged over the two following weeks. Variations also occur according to age and cause of death. The effect of temperature is greater in persons aged over 70 years of age, and it is also greater in cases of circulatory and respiratory diseases.
A statistically significant association has been found between temperature and mortality. This relationship is not monotonic, but mortality increases in proportion to the variance in ambient temperature from a range of temperatures that varies from winter to summer.
极低和极高的环境温度均与死亡率升高相关。本研究评估了瓦伦西亚市每日死亡人数与环境温度变化之间的关系。
使用自回归泊松回归，对季节性、星期几、节假日、空气污染、流感发病率和湿度进行控制，将瓦伦西亚市内所有原因导致的每日死亡人数（总死亡人数以及仅70岁以上人群的死亡人数），以及特定原因导致的死亡人数（如心血管和呼吸系统疾病、恶性肿瘤以及除外部原因外的所有原因）与日均温度相关联。在回归模型中，温度作为两个互补变量进行测量：“热”和“冷”；还考虑了它们在测量后长达2周的延迟效应。
图形分析揭示了温度与死亡率之间随年份时间的关系。在较凉爽的月份（11月至4月），死亡率最低时的温度为“最低温度”（即约15摄氏度），而在较温暖的月份（5月至10月），则出现在约24摄氏度左右。因此，根据涉及的两个季节中的哪一个，对“热”和“冷”变量采用不同值进行分层分析。在一年中较冷的月份，较高温度往往对死亡率产生快速影响，而较低温度的影响则更为延迟。在炎热季节，热变量更明显地表现出一种效应，并且这种效应会在接下来的两周内持续。根据年龄和死亡原因也会出现差异。温度对70岁以上人群的影响更大，对循环系统和呼吸系统疾病患者的影响也更大。
已发现温度与死亡率之间存在统计学上的显著关联。这种关系不是单调的，而是死亡率与环境温度从冬季到夏季变化范围内的方差成比例增加。
