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Physiologic and behavioral rhythms are universal, involving most of the body’s systems and affecting the timing of the symptoms and signs of disease. Using 5 years of stroke registry data from Iwate prefecture, Japan, these authors tabulated the time of stroke onset for nearly 13,000 patients experiencing either their first ischemic infarction (7575 patients), first intracerebral hemorrhage (3852 patients), or first subarachnoid hemorrhage (1530 patients); all were diagnosed using CT or MRI scans. (Stroke reported upon awakening, which included onset during sleep, was considered perceived onset at awakening.)
A peak in perceived symptom onset occurred in the morning (from 6:00 AM to 8:00 AM) for both infarcts and hemorrhages. For both types of hemorrhagic stroke, a second, higher peak was present in the late afternoon and early evening (from about 4:00 PM to 8:00 PM). Perceived onset upon awakening accounted for about 20% of all infarcts.
Omama S et al. Differences in circadian variation of cerebral infarction, intracerebral haemorrhage and subarachnoid haemorrhage by situation at onset. J Neurol Neurosurg Psychiatry 2006 Dec; 77:1345-9.
Comment
The practical importance of human circadian rhythmicity, and its consequences for health and disease, are now being recognized. Cerebrovascular risk is known to be time-dependent, with morning vulnerability correlated with increases in blood pressure, circulating catecholamine levels, and hypercoagulability. That hemorrhagic events also exhibit a dramatic second peak later in the day is made clear in this study, which was made possible by the large number of cases in an unbiased, population-based sample. These data are a first step toward identifying candidate trigger factors — physiologic, hormonal, behavioral, and even cultural — that lead to the onset of different stroke subtypes. The findings should help lead to the proper timing of possible countermeasures.