-Original-

Ambient Temperature Change Increases in Stroke Onset: Analyses Based on the Japanese Regional Metrological Measurements

Ichiro Takumi^1,2, Masahiro Mishina^2,3, Shushi Kominami², Takayuki Mizunari², Shiro Kobayashi², Akira Teramoto^4,5 and Akio Morita⁵

¹Department of Neurosurgery, Nippon Medical School Musashi Kosugi Hospital
²Neurological Institute, Nippon Medical School Chiba Hokusoh Hospital
³Department of Neuro-pathophysiological Imaging, Graduate School of Medicine, Nippon Medical School
⁴Tokyo Rosai Hospital
⁵Department of Neurosurgery, Graduate School of Medicine, Nippon Medical School

Background: Relationships between various climate factors and stroke have long been a subject of investigation. The present study investigated in a single medical center the effects of periodic temperature changes on the onset of intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), atherothrombotic infarction (AI), lacunar infarction (LI), cardiogenic embolism (CE), and transient ischemic attack (TIA).
Methods: The subjects were 4,310 patients who had been hospitalized because of hemorrhagic or ischemic stroke from January 2000 through December 2005. Ambient temperature data were collected from the Japan Meteorological Agency Database. The following factors were analyzed: number of stroke onsets per day; mean, maximum, and minimum ambient temperatures; and differences between the mean temperatures on the onset day and the previous week. Relationships between temperature factors and totals based on stroke subtypes were assessed by means of regression analyses with a standard least squares model controlling for specific covariates.
Results: The daily admissions for ICH, SAH, AI, LI, and CE increased when the mean temperature on the onset day was 1°C lower than that of the previous week. Decreases in minimum ambient temperature predicted increased numbers of admissions for ICH and for SAH. Conversely, a 1°C increase in maximum ambient temperature significantly affected ICH, AI, and CE admissions. There was no definitive relationship between temperature change and admissions for TIA.
Conclusion: Both absolute and comparative changes in ambient temperature are related to increased onsets of hemorrhagic and ischemic stroke in Japan.

J Nippon Med Sch 2015; 82: 281-286

Keywords
ambient temperature, weather, hemorrhagic stroke, ischemic stroke

Correspondence to
Ichiro Takumi, MD, PhD, Department of Neurological Surgery, Nippon Medical School Musashi Kosugi Hospital, 1-396 Kosugi-cho, Nakahara-ku, Kawasaki, Kanagawa 211-8533, Japan
takumi@nms.ac.jp

Received, July 20, 2015
Accepted, November 10, 2015