title: Morning surge in circadian periodicity of ischaemic stroke is independent of conventional risk factor status: findings from the Takashima Stroke Registry 1990-2003.
abstract: BACKGROUND
  We examined the circadian periodicity of ischaemic stroke (IS) onset and its relationship with conventional risk factors using 14-year stroke registration data.
  
  
  METHODS
  Ischaemic stroke event data were acquired from the Takashima Stroke Registry, which covers a stable population of approximately 55,000 in Takashima County in central Japan. During 1990-2003 there were 637 (353 men and 284 women) cases with classifiable onset time. IS incidence was categorized as occurring at night (midnight to 6 am), morning (6 am to noon), afternoon (noon to 6 pm), and evening (6 pm to midnight). The OR (with 95% CI) of having an IS in the morning, afternoon, and evening were calculated, with night serving as reference.
  
  
  RESULTS
  There was significant diurnal variation in IS incidence (P < 0.001). The proportion of events was highest in the morning (40.7; 95% CI: 36.9-44.5), and lowest in the night (14.0; 95% CI: 11.5-16.9). In the morning an excess incidence of IS was observed in both genders, in subjects <65 years and > or =65 years, and in all IS subtypes. The morning excess of IS incidence was similar across seasons and days of the week. For all IS, morning excess was higher (odds ratio: 2.91; 95% CI: 2.29-3.70) compared to the night period. Similar trends persisted after adjusting for age, gender, and risk factors.
  
  
  CONCLUSIONS
  In the examination of circadian variation of IS onset, a predominant morning peak independent of conventional risk factors was observed in a Japanese population with similar pattern across seasons of the year and days of the week.
authors.affiliation: Shiga University of Medical Science, Shiga, Japan. turin@belle.shiga-med.ac.jp
authors.forename: T C
authors.initials: TC
authors.lastname: Turin
authors.forename: Y
authors.initials: Y
authors.lastname: Kita
authors.forename: N
authors.initials: N
authors.lastname: Rumana
authors.forename: N
authors.initials: N
authors.lastname: Takashima
authors.forename: M
authors.initials: M
authors.lastname: Ichikawa
authors.forename: H
authors.initials: H
authors.lastname: Sugihara
authors.forename: Y
authors.initials: Y
authors.lastname: Morita
authors.forename: K
authors.initials: K
authors.lastname: Hirose
authors.forename: Y
authors.initials: Y
authors.lastname: Murakami
authors.forename: K
authors.initials: K
authors.lastname: Miura
authors.forename: A
authors.initials: A
authors.lastname: Okayama
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: R D
authors.initials: RD
authors.lastname: Abbott
authors.forename: H
authors.initials: H
authors.lastname: Ueshima
mesh_terms: D000367:Age Factors; D002940:Circadian Rhythm / Q000502:physiology*; D016001:Confidence Intervals; D005260:Female; D006331:Heart Diseases / Q000150:complications; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D020521:Stroke / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology*; D013997:Time Factors