Morning surge in circadian periodicity of ischaemic stroke is independent of conventional risk factor status: findings from the Takashima Stroke Registry 1990-2003.
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.
Turin
T C
TC
Shiga University of Medical Science, Shiga, Japan. turin@belle.shiga-med.ac.jp
Kita
Y
Y
Rumana
N
N
Takashima
N
N
Ichikawa
M
M
Sugihara
H
H
Morita
Y
Y
Hirose
K
K
Murakami
Y
Y
Miura
K
K
Okayama
A
A
Nakamura
Y
Y
Abbott
R D
RD
Ueshima
H
H
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