You can't bank sleep: researchers

Sleeping in to recover after chronic sleepless nights won't work, a new study suggests.

The study was designed to look at the effects of short- and long-term sleep loss and its effect on performance, such as reaction time.The results appear in Wednesday's issue of the journal Science Translational Medicine.

'Don't think you can just bank up your sleep on the weekend, because it doesn't work that way.' Shelby Freedman Harris

"We know that staying awake 24 hours in a row impairs performance to a level comparable to a blood-alcohol content beyond the legal limit to drive," said lead researcher Dr. Daniel Cohen of Boston's Brigham and Women's Hospital.

When people who are chronically sleep deprived pull an all-nighter, "the deterioration is increased tenfold," added Cohen, who is also a neurologist at Harvard Medical School.

The researchers studied nine healthy volunteers, five men and four women, for 38 days. In the name of science, the volunteers stayed awake for 33-hour stretches with 10 sleeps in-between. The schedule was the equivalent of getting 5.6 hours of sleep in 24 hours while allowing researchers to test catch-up nights.

While most participants caught up after acute sleep loss with one good night of 10 hours of sleep, those with chronic sleep loss showed deteriorating performance for each hour spent awake.

These people were vulnerable to errors and accidents, particularly during the late night, the team found.

People may feel like they recovered when they awake, unaware that they are chronically sleep-deprived, Cohen said.

The difference was measured on the scale of milliseconds, enough to make a difference in hitting the brakes in time to prevent a collision.

The findings suggest that sleep loss affects the brain in at least two ways one that builds over normal waking hours, and another that accumulates over days or weeks of failing to get enough shuteye.

The findings are important for those who work odd hours and think they can get by with a few hours of sleep on weeknights, said Shelby Freedman Harris, behavioural sleep-medicine director at New York's Montefiore Medical Center, who was not involved with the new research.

"Don't think you can just bank up your sleep on the weekend, because it doesn't work that way," Harris said.