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Different strokes occur at different times

Different types of strokes occur most often at different times of day say scientists at Iwate Medical University in Iwate, Japan.

The team based their findings on data from 12,957 cases of first-ever stroke diagnosed by CT or MRI scans and drawn from the Iwate Stroke Registry between 1991 and 1996.The researchers chose patients who had experienced cerebral infarctions, or ischemic strokes, where cells die because blood flow to the brain is restricted, and two kinds of hemorrhagic strokes: intercerebral hemorrhages that occur within the brain, and subarachnoid hemorrhages that occur in arteries at the brain's surface.

The wake-sleep cycle (circadian rhythm) was divided into 12 two-hour intervals. All three types of stroke had peaks between 6 and 8 in the morning and 6 and 8 in the evening with fewer incidents during sleep when blood pressure is the lowest. But cerebral infarctions had a higher peak in the morning and a lower peak in the afternoon and the two hemorrhagic strokes had a higher peak in the afternoon and a lower peak in the morning.

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