An Ecological Study Of The Relationship Between Mean Temperature And Mortality For Stroke In Elderly People

Abstract

BACKGROUND: Several studies have shown the influence of climatic variables on hospital admissions and mortality from stroke. Since the organism of the elderly are more susceptible to changes in temperature, the aim of this study was to investigate the influence of temperature on stroke mortality in elderly people in São Paulo. METHODS: Daily mortality for stroke, meteorological variables and air pollution data were obtained for the period of January 2002 to December 2011. The percentage increase of mortality for total stroke, hemorrhagic, and ischemic were estimated with endpoint-specific generalized additive Poisson regression models. Effects of mean temperature, humidity, thermal amplitude, barometric pressure and air pollutants were assessed using specific third-degree polynomial distributed lag models for a time window of eight days. The models were controlled for humidity, atmospheric pressure, thermal amplitude and pollutants. RESULTS: In the ten years of study mortality from stroke was more than 55,000. To an increase in mean temperature of 1ºC we observed an estimated increase of mortality for stroke in elderly of 1.3% (CI 95%, 0.6-2.0) in total stroke mortality for each interquartile range increase for increase of 1ºC in mean temperature in the first two days. For women the increase was 7.8% (CI 95%, 3.1-12.7) and for men 1.1% (CI 95% 0.1-2.2). Ischemic stroke mortality also increased 14.1% (CI 95%, 8.1-20.4) for each 1ºC increase in mean temperature. Just for women the increase was 4.7% (CI 95%, 0.6-8.9) for each interquartile range. For hemorrhagic stroke no significative association was observed with mean temperature. CONCLUSION: The mean temperature affects total stroke mortality and ischemic stroke subgroup in elderly and, especially, in women. This reinforces the concept that the subgroups of stroke, ischemic and hemorrhagic, may present different pathophysiologic mechanisms and, hence, different risk factors.