People who suffer strokes in their sleep are prevented from receiving clot-busting drugs because the exact time of the attack cannot be pin-pointed. According to a new report produced by the University of Cincinnati, individuals who have strokes when they are sleeping are unable to take treatments which can prevent permanent disability because the four-and-a-half hour time window in which they must be taken can’t be identified. This problem affects the 15 per cent of stroke victims who suffer attacks while sleeping –with an estimated 58,000 Americans arriving in emergency rooms each year having experienced stoke symptoms during slumber. When comparing wake-up stroke victims and those who had been asleep no major differences were found in the study, though there was a tendency for those who suffered wake-up stokes to be slightly older and to have attacks which were slightly more severe. Study author, Dr. Jason Mackey of the University of Cincinnati, said: "These wake-up strokes look a lot like the other strokes we see."