Numbers of Stroke Patients and Stroke Subtypes According to Highest and Lowest Daily Temperatures in Seoul

BACKGROUND AND PURPOSE There is conflicting evidence for whether or not the incidence of stroke is influenced by the daily temperature. The association between daily temperature and incidence of stroke is largely unknown in Korea. This study attempted to evaluate whether the maximum or minimum daily temperature is associated with increased numbers of strokes and stroke subtypes among Seoul residents. METHODS We obtained the maximum and minimum daily temperatures in Seoul from the Korean Meteorological Administration between January 2005 and December 2014. Consecutive patients with acute stroke were registered who visited the emergency room or outpatient clinic in Soonchunhyang University Hospital, Seoul. The residential addresses of cases were restricted to within a 2-kilometer radius of this hospital. The stroke events were prospectively recorded with onset time, and were classified by subtypes. The categories of daily temperature were divided by 10℃ from the mean temperature. The mean daily number of strokes was calculated during the study period. One-way analysis of variance and Duncan's post-hoc test were applied to compare the number of strokes among the temperature groups. RESULTS In total, 2,313 acute strokes were identified during the period: 1,643 ischemic strokes and 670 hemorrhagic strokes. The number of cases was significantly higher when the maximum daily temperature was >32℃ or ≤3℃ (p=0.048) or the minimum daily temperature was ≤-11.0℃ (p=0.020). The lowest maximum daily temperature was associated with increased instances of intracerebral hemorrhage (p=0.029) and small-vessel occlusion (p=0.013), while the highest maximum daily temperature was associated with an increased instance of large-artery atherosclerosis (p=0.045). CONCLUSIONS The daily temperature had measurable and different associations with the number of strokes and strokes subtypes in Seoul, Korea.