title: Weekly variations of stroke occurrence: an observational cohort study based on the Kyoto Stroke Registry, Japan.
abstract: OBJECTIVE
  Understanding the temporal pattern of stroke onset and exploring the possible triggers are important strategies to reducing the incidence of stroke. If stroke occurs frequently on a specific day of the week, it is assumed that other factors, that is, 'triggering factors', induce stroke. The aim of the study is to investigate differences in the incidences of stroke among days of the week.
  
  
  METHODS
  Hospital-based registry stroke over an 11-year period.
  
  
  METHODS
  Kyoto Prefecture, Japan.
  
  
  METHODS
  A total of 13,788 patients with stroke identified from January 1999 to December 2009 inclusive in the entire Kyoto Prefecture and registered in the Kyoto Stroke Registry (KSR).
  
  
  METHODS
  Patients with stroke were classified into seven groups based on the day of the week on which stroke developed. We confirmed the differences in the incidence among days using the χ(2) test and then performed multinomial logistic analysis referring to the stroke incidence on Sunday to calculate the OR and 95% CI of the stroke occurrence on each day of the week.
  
  
  RESULTS
  The OR (95% CI) for stroke occurring on Monday, Tuesday, Wednesday, Thursday, Friday and Saturday was 1.157 (1.030 to 1.293), 1.101 (0.981 to 1.236), 1.059 (0.943 to 1.188), 1.091 (0.972 to 1.225), 1.053 (0.938 to 1.205) and 1.074 (0.956 to 1.205), respectively. After stratification by stroke subtypes, cerebral infarction occurred more frequently on Monday than on Sunday (OR and 95% CI were 1.189 and 1.034 to 1.366, p=0.014) independent of age and gender. There was no significant day of the week variation in cerebral haemorrhage or subarachnoid haemorrhage.
  
  
  CONCLUSIONS
  Some factors that arise periodically appear to affect the incidence of cerebral infarction, which gradually develops over years, and this suggests an aetiological mechanism different from the conventional cumulative effect of risk factors due to long-term exposure. We propose a hypothesis that there is a 'triggering factor' for the development of cerebral infarction.
authors: Department of Neurology, National Hospital Organization, Minami Kyoto Hospital, Kyoto, Japan.
authors: Kazuo
authors: K
authors: Shigematsu
authors: Department of Epidemiology for Community Health and Medicine, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, Japan.
authors: Yoshiyuki
authors: Y
authors: Watanabe
authors: Department of Neurosurgery, Kyoto Kidugawa Hospital, Kyoto, Japan.
authors: Hiromi
authors: H
authors: Nakano
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002543:Cerebral Hemorrhage / Q000150:complications / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology* / Q000209:etiology
keywords: EPIDEMIOLOGY