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Triggering of Ischemic Stroke Onset by Decreased Temperature : A case-crossover study

Background and Purpose: Some studies suggest that low temperatures can affect mortality, especially deaths associated with circulatory and respiratory condition. The authors investigated the association between ischemic stroke onset and low temperatures in 545 patients over a 3-year period (January 1998 to December 2000) in Incheon, Korea. Methods: We chose to use a case-crossover study design to assess the changes in the risk of ischemic stroke during a brief hazard period after exposure to a temperature change. For each subject, 1 case period was matched to 2 control periods exactly 1 week apart before and after the date and time of the onset of the ischemic stroke. Results: Decreased ambient temperature was found to be associated with the risk of acute ischemic stroke. One day after being exposed to cold weather, we found a statistically significant increase of odds ratio to 2.38 (95% CI 1.33, 4.35) for the onset of an ischemic stroke for an interquartile range decrease in temperature. The elevated risk period was 24 to 54 hours after cold exposure. Risk estimates associated with decreased temperature were found to depend on the season, and to be greater in the winter than in the summer. We also found that women, the elderly, and those with hypertension, hypercholesterolemia, or no prior history of stroke are more susceptible to cold-induced ischemic stroke. We suggest that stroke incidence rises with falling temperature, and that even a moderate decrease can lead to a higher occurrence of ischemic stroke. We noted that the impact of cold on stroke incidence was greatest one day after the fall in temperature.