Circadian variation in acute ischemic stroke: a hospital-based study.

BACKGROUND AND PURPOSE We investigated circadian rhythm in ischemic stroke onset and its subtypes, differentiating between first-ever stroke and recurrent stroke. METHODS A consecutive series of 1223 patients with ischemic stroke was admitted at 2 reference hospitals; the time of onset of symptoms was obtained, differentiating between onset while asleep and awake. We compared circadian rhythm between stroke types and between first-ever and recurrent stroke. RESULTS The onset time was known in 914 patients; 25.6% experienced onset on awakening [higher incidence in thrombotic and lacunar stroke (28.9% and 28.4%, respectively) than in embolic stroke (18.8%)]. For all stroke subtypes, there was a significant diurnal variation, with a morning peak between 6 AM and noon; after redistributing the hour of onset of patients awakening with stroke, the morning peak was minimal in all types of stroke. There were no differences in circadian rhythm between patients with first-ever and recurrent stroke. CONCLUSIONS Only hospitalized patients were studied. There is a circadian rhythm in all types of stroke, with higher frequency during the day and lower frequency in the last hours in the evening. The highest incidence in the early hours of the morning can be overestimated, due to patients who awaken with stroke. There is no difference in circadian rhythm between first-ever stroke and recurrent stroke.