Study shows 14 per cent of all strokes occur during sleep

According to a new study, approximately 14 per cent of all strokes occur during sleep, preventing many from getting clot-busting treatment.

"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," said study author Jason Mackey, of the University of Cincinnati and a member of the American Academy of Neurology.

In their study researchers examined all cases of ischemic strokes in people aged 18 and older in hospital emergency departments. They found that the majority of strokes were ischemic strokes caused by blocked blood flow in the brain.

Of the 1,854 ischemic strokes studies, 273, or 14 per cent, were found to be "wake-up strokes," in which the person woke up with stroke symptoms. Extrapolating the number to the general population of the US the researchers say that around 58,000 people in the US go to the emergency department with a wake-up stroke in a year.

On analysing whether those with wake-up strokes would have been eligible for the clot-busting drug tissue plasminogen activator, or PA, if the time of stroke onset had been available, they found that at least 98 would have been eligible for treatment.

"This is a group of patients that should be a focus for future studies. It's likely that some of these strokes occurred immediately prior to awakening, and people would benefit from treatment," Mackey said.

The study also revealed a slight link between age and stroke severity. The wake-up stroke patients had an average age of 72, as against 70 for the other individuals. The average score of the wake-up stroke patients was four, as against three among those whose symptoms appeared while they were awake. A mild stroke carries a score of one to four.