Ambient Temperature and Stroke Risk among Elderly Individuals in Israel

ABSTRACT

Background Stroke is a leading cause of morbidity and mortality in the Western world. We examined the association between weather conditions and stroke risk by season and stroke type in Israel.

Methods The study sample comprised of all individuals aged ≥50 years who had a stroke reported to the National Stroke Registry between 2014 and 2016. We retrieved data on temperature and humidity from the Israel Meteorological Service and air quality from the monitoring stations of the Israel Ministry of Environment Protection. We utilized time-stratified case-crossover study design to assess the relationship between Heat Index (HI; combination of mean temperature and humidity) and stroke risk while adjusting for particulate matter (PM_2.5). The main statistical model was conditional logistic regression, in which each person serves as his/her own control.

Results The sample for the analysis included 27,834 individuals who had a stroke during the study period (mean age 74±11 years; 14,812 (53%) males; 1,944 Intracerebral Hemorrhage, 17,877 Ischemic and 8,003 Transient Ischemic Attacks). In summer, high HI was related to increased stroke risk starting from 4 days prior to the stroke event, and this risk gradually increased until day 7 prior to stroke (OR=1.05 95% CI 1.04-1.07). In winter, high HI was linked with decreased stroke risk starting from day 2 before the event which also gradually decreased until day 7 (OR=0.95 95% CI 0.94-0.96). The positive and negative associations in summer and winter, respectively, were observed for all stroke types except for Hemorrhagic stroke which was not associated with increased HI in the summer.

Conclusions Hot and cold days in the summer and winter, respectively, may increase stroke risk in subsequent days in Israel. Timely interventions to reduce exposure to extreme weather conditions among elderly individuals may lead to stroke prevention in times of climate change.

Keywords Heat Index, Stroke, Stroke type, Time-stratified case-crossover design