May 9, 2011 -- Many people who suffer strokes have them while they are asleep, which may prevent them from getting clot-busting treatment in the critical first few hours after a stroke, a study shows.
Such strokes, referred to as wake-up strokes, account for about 14% of all strokes, according to the study. Previous research estimated the percentage of wake-up strokes between 8% and 28%.
The new research was based on 1,854 ischemic strokes -- strokes caused by blood clots -- seen in emergency departments in the greater Cincinnati and Northern Kentucky region.
The study is published in the May 10 issue of Neurology, the medical journal of the American Academy of Neurology.
Of the 1,854 strokes in the study, 273 (14%) were wake-up strokes. By extrapolating that number to the general U.S. population, the researchers estimate that 58,000 people in the U.S. go to emergency rooms and urgent care departments with a wake-up stroke every year.
“Because the only treatment for ischemic stroke must be given within a few hours after the first symptoms begin, people who wake up with stroke symptoms often can’t receive the treatment since we can’t determine when the symptoms started,” study researcher Jason Mackey, MD, of the University of Cincinnati, says in a news release. “Imaging studies are being conducted now to help us develop better methods to identify which people are most likely to benefit from treatment, even if symptoms started during the night.”
The researchers compared people who reported to emergency departments with wake-up strokes to those who had strokes while awake. No differences were noted between the two groups in terms of sex, whether they were married or living with a partner, and their stroke risk factors, such as high blood pressure, diabetes, smoking, or high cholesterol.
Researchers say they noticed minor differences in age and severity of the wake-up strokes.
People with wake-up strokes were an average of 72 years old, compared to 70 for people who had strokes while awake.
Researchers say the people with wake-up strokes had an average score of 4 on a test of stroke severity vs. 3 for those who had strokes while awake. Scores from 1 to 4 on the scale indicate mild strokes.
Many of those in the study with wake-up strokes would have been eligible for clot-busting drug treatment if the time of onset of symptoms had been available. The study says that of the 273 people who had wake-up strokes, at least a third would have been eligible for this critical treatment.
“This is a group of patients that should be a focus for future studies,” Mackey says. “It’s likely that some of these strokes occurred immediately prior to awakening, and people would benefit from treatment.”