Are there any unique epidemiological and vascular risk factors for ischaemic strokes that occur in the morning hours?

It is now accepted that the incidence of ischaemic stroke is significantly increased in the morning. Any attempts to prevent its occurrence must be ba sed on determining the mechanisms, special risk factors and appropriate pro tective measures needed during this vulnerable period. We studied the epide miological features of morning stroke and reviewed the records of 2312 cons ecutive patients recorded prospectively in the Tel Aviv Stroke Register. In formation about time of stroke onset was obtained from the patient, family members or other observers. The study parameters of age, sex, vascular dist ribution (carotid versus vertebrobasilar), ischaemic heart disease, myocard ial infarction, diabetes mellitus, arterial hypertension, smoking, hyperlip idaemia, stroke severity and recurrence were compared between patients with morning stroke and those with stroke occurring at other times. In 599 pati ents (34%) stroke occurred between 06:00 and 10:00 h. No evaluated paramete r was found to be statistically different among the morning stroke patients compared with stroke occurring at other times (P < 0.2). Patients with art erial hypertension and ischaemic heart disease and male patients had a grea ter likelihood of stroke occurrence between 22:00 and 02:00 h (P < 0.05). O ut data suggest that none of the common vascular risk factors could explain the morning peak of stroke occurrence. The next step in the quest for unde rstanding the phenomenon of circadian variation is to identify other physio logical factors and the effects of pharmacological agents in morning stroke protection.