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

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Abstract
It is now accepted that the incidence of ischaemic stroke is significantly increased in the morning. Any attempts to prevent its occurrence must be based on determining the mechanisms, special risk factors and appropriate protective measures needed during this vulnerable period. We studied the epidemiological features of morning stroke and reviewed the records of 2312 consecutive patients recorded prospectively in the Tel Aviv Stroke Register. Information about time of stroke onset was obtained from the patient, family members or other observers. The study parameters of age, sex, vascular distribution (carotid versus vertebrobasilar), ischaemic heart disease, myocardial infarction, diabetes mellitus, arterial hypertension, smoking, hyperlipidaemia, stroke severity and recurrence were compared between patients with morning stroke and those with stroke occurring at other times. In 599 patients (34%) stroke occurred between 06:00 and 10:00 h. No evaluated parameter was found to be statistically different among the morning stroke patients compared with stroke occurring at other times (P < 0.2). Patients with arterial hypertension and ischaemic heart disease and male patients had a greater likelihood of stroke occurrence between 22:00 and 02:00 h (P < 0.05). Our 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 understanding the phenomenon of circadian variation is to identify other physiological factors and the effects of pharmacological agents in morning stroke protection.