Around 30 healthy adult volunteers took part in the study in which they were placed on a 13-day schedule during the first four days of which they were allowed to sleep for eight hours a day. For the next six days, the volunteers were woken up after just six hours while on the final two days, they were allowed to sleep for 10 hours in a day in order to recover from their lack of sleep on the preceding days.
The researchers monitored the volunteers' health and performance using a variety of different tests on three different days during the period and found that after five days of deprived sleep, the volunteers were sleepier on both objective and subjective tests compared to baseline levels. The researchers also found that while the sleepiness went away after the extra sleep recovery period, their ability to pay attention had also deteriorated during the period and did not improve after the recovery.
"Two nights of extended recovery sleep may not be sufficient to overcome behavioral alertness deficits resulting from mild sleep restriction. This may have important implications for people with safety-critical professions, such as health-care workers, as well as transportation system employees (drivers, pilots, etc.) The long-term effects of a repeated sleep restriction/sleep recovery weekly cycle in human remains unknown", the researchers wrote in their report.