Circadian and Seasonal Variation in the Incidence of Intracerebral Hemorrhage

We studied the time of onset of spontaneous supratentorial intracerebral hemorrhage, with regard to the time of the day and the season, in 157 consecutive patients. Intracerebral hemorrhage occurred more often during the daytime (6 a.m. - 6 p.m.) than during the evening and night (p < 0.01). No seasonal variation was found in the group as a whole, in subgroups with a history of hypertension (n = 59), or with age below or above 65 years. A rise in blood pressure contributes to the pathogenesis of intracerebral hemorrhage, but is not a necessary factor.