title: Absolute temperature, temperature changes and stroke risk: a case-crossover study.
abstract: Studies suggest that there is an association between weather patterns and ischemic stroke risk. Exposure to a sudden decrease in temperature may increase stroke risk through altering blood viscosity and/or by triggering infections. We investigated the association between ischemic stroke risk and change in temperature. We used a case-crossover study design with 303 consecutive patients admitted to Heidelberg University, Department of Neurology over a one and a half year period (Aug 1998-Jan 2000). We used one day before stroke as the hazard (case) period matched to two control periods 2-7 days before and after stroke onset and took both ambient maximum temperature and the 24-hour difference in maximum temperature as exposure. There was no risk associated with ambient maximum temperature at all lag times and in all subgroup analyses. For the 24-hour difference, large changes in temperature (>5 degrees C) were associated with an increased risk of acute ischemic stroke regardless of whether the change was negative or positive. The odds ratio for temperature increases >5 degrees C compared to no change in temperature was 2.0 (95% confidence interval (CI): 0.7-5.9) at a lag time of 3 days. We found no relevant relation between temperature and stroke risk. The results suggest that the risk of ischemic stroke may increase with large day-to-day variations upwards or downwards in temperature.
authors.affiliation: Department of Tropical Hygiene and Public Health, University of Heidelberg, Heidelberg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Kyobutungi
authors.forename: A
authors.initials: A
authors.lastname: Grau
authors.forename: G
authors.initials: G
authors.lastname: Stieglbauer
authors.forename: H
authors.initials: H
authors.lastname: Becher
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018592:Cross-Over Studies; D003627:Data Interpretation, Statistical; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology* / Q000503:physiopathology; D013696:Temperature; D014887:Weather