WASHINGTON – Sleeping in on Saturday after a few weeks of too little shuteye may feel refreshing, but it can give a false sense of security.

New research shows chronic sleep loss can't be cured that easily. Scientists teased apart the effects of short- and long-term sleep loss — and found that the chronically sleep-deprived may function normally soon after waking up, but experience steadily slower reaction times as the day wears on, even if they had tried to catch up the previous night. More