Weather and Stroke in a Subtropical Area: Ilan, Taiwan

Abstract

Background and Purpose The aim of this study was to clarify the association of weather and stroke occurrence in a subtropical area in Ilan, Taiwan. Methods We studied 517 patients with stroke (date of onset, January 1 to December 31, 1991) in Poh-Ai Hospital and St Mary’s Hospital: 316 patients (61.1%) with cerebral infarction, 170 (32.9%) with intracerebral hemorrhage, and 31 (6.0%) with other types of stroke. The daily occurrence of cerebral infarction and intracerebral hemorrhage was analyzed and correlated with three major meteorologic factors: air temperature, air pressure, and relative humidity. Results The occurrence of cerebral infarction was rather uniform in all kinds of weather. The occurrence of intracerebral hemorrhage was approximately twice as great on cold days (0.71 case per day) and high-pressure days (0.73) as on warm days (0.31) and low-pressure days (0.39) ( P <.005 by χ 2 test). When a linear regression model was used to test whether air temperature or air pressure had more influence on intracerebral hemorrhage, only air temperature showed a significant effect. Regarding intracerebral hemorrhage, the relative risks of cooler and median temperature days versus warmer days were 18.5 and 5.1, respectively. Conclusions Intracerebral hemorrhage but not cerebral infarction occurs more frequently on cooler days, with a dose-response relationship, in Ilan, Taiwan.