Why sleeping in will create another type of sleep debt

The type of sleep debt you are creating by sleeping up late is NOT replaceable by the type of sleep you get by sleeping in.

Our sleep follows a pattern of 90 min cycles. But overnight, the structure of this cycle changes as the night progresses. 

• In the first part of the night, the 90 min cycles are filled with mostly NREM deep and restorative sleep.

• As the night progresses, the NREM sleep makes room for REM sleep, which will dominate a big part of the 90 min.

If you go to bed generally at 10:30 PM but stay up late until 12 AM, you will lose 1 sleep cycle of MAINLY DEEP, restorative NREM (Stage 3 and Stage 4) sleep. 

If you sleep in in the morning, you will get more REM sleep, so even if you slept 8 h, you would NOT feel physically refreshed. 

The sleep debt you created in the few days of sleeping poorly during the week can’t be compensated by sleeping in on weekends. You will never catch up with the type of sleep you lost.

The type of sleep debt you are creating by sleeping up late is NOT replaceable by the type of sleep you get by sleeping in.