Staying in bed for as long as possible during the weekend can be very healthy for the exhausted brain of too many people that do not sleep enough during the working days.

Nevertheless, an extensive study by Pennsylvania University demonstrates that more than one night sleep is required for a complete recovery of the “sleep deficit” and the capacities they have started to lose in the process.

After sleeping only four hours a day –from 4am to 8am- for five consecutive days, the volunteers of this study consistently shown neuroconductual damage such as atention loss or slow reactions.

The sixth night, some of the volunteers slept for 10 hours, while others slept a bit less and some others did not sleep at all.

As expected, the recovery of lost capacities was in agreement with the sleeping time: the best results were achieved by those who slept the most. But the most interesting discovery is that, even though they got the best results, they did not manage to fully recover their capacities, because of the accumulation of tiredness from previous days.

Following these results, the authors of this study conclude that “mental deterioration caused by a regular lack of sleep -depending on how big the lack of sleep is- can be as serious as a total deprivation of sleep”. They also conclude that “the effects of the lack of sleep (…) prolongs itself in time for more than one day”.

Residual Sleep Debt

“Sleep deprivation is severe enough to impede a full recovery after only one night sleeping more hours. This indicates that there is a residual sleep debt”, says the expert in Experimental Psychiatry David Dinges, main author of the study published by “Sleep” magazine.

The root of the problem is the following: Even though sleeping one or two hours more than the recommended eight is refreshing when there is some lack of sleep from previous nights, it is not possible to fully recover “the sleep deficit” on one go, since the biologic rhythms make difficult to rest for more than 10 consecutive hours.

This study was performed on 159 healthy adults with ages between 22 and 45 years old with an average of 30 years old. None of these individuals had ever had sleep problems and they spent 12 days in the lab. In total the study covered 2.000 days of experimentation, which makes it the biggest study of this kind ever done.