Strokes may be timed to the body's internal clock,
Japanese researchers say.
Researchers at Iwate Medical University analyzed
data from 13,000 patients who had one of three
types of stroke -- cerebral infarction, subarachnoid
hemorrhage, intracerebral hemorrhage -- for the
first time.
All three kinds of strokes had two periods of
peak occurrence: one between 6 a.m. and 8 a.m.
and another between 6 p.m. and 8 p.m. Stroke occurrence
declined significantly during sleep.
Upon closer analysis, the researchers did find
that cerebral infarction -- where blood flow to
the brain is restricted -- had a higher peak in
the morning and a lower peak in the afternoon
than the other two kinds of stroke, which were
more likely to have lower peaks in the morning
and higher peaks in the afternoon.
About 20 percent of cerebral infarction occurred
during sleep, with most of them concentrated in
the time immediately before waking up, although
it's likely the stroke would have actually begun
earlier, the study authors said.
The findings were published in the Aug. 17 online
edition of the Journal of Neurology, Neurosurgery
and Psychiatry.
