Tuesday, March 15, 2011

Sleep debt?

The idea of Sleep Debt is that each person has a "sleep quota" (an amount that he/she is supposed to sleep). If you sleep less than your sleep quota, you'll feel crummy until you sleep more to pay it back. I guess there are a few variants of Sleep Debt theory:
1. It's a straight balance. If your quota is 8 hours, and you sleep 7 hours for 10 days, you'll have 10 hours to pay back, and you won't feel good until you sleep 9 hours for 10 days (or 10 hours for 5 days, or whatever).
2. Sleep debt exists, but it's not a straight balance; a couple days of sleep-as-long-as-you-want will cure you.
3. There is no sleep debt, only REM sleep debt.
4. It's a myth. (tiredness might be caused by too little sleep, but it might equally be caused by boredom or whatever.)

There seem to be variations of Sleep Quota theory too:
1. We all have about the same sleep quota, and it's always been the same.
2. We all have about the same sleep quota, and it's changed in modern times.
3. We all have different sleep quotas.

I'm skimming abstracts here, because I'd like to externalize some thoughts and move on.
Klerman and Dijk, 2005, argue that sleep debt exists, that it persists at least over 3 days, and that our sleep quotas are about the same.
Sallinen et al, 2008, found that one night isn't enough to recover back to normal from sleep deprivation.
Wehr et al, 1993, found that long nights led to longer sleep, over a long duration of time. They did have a short bump to 10 or 11 hours before evening out to about 8, which does support the "sleep debt that fixes quickly". (see fig. 10 here, if you can)
Carskadon and Dement, 1981, agree. One night's rest returns you to baseline. (Dement gave a tech talk at Google a couple years ago; long and not worth watching.
Dinges et al, 1997, show that sleep debt does accumulate, without reaching an asymptote.
Randy Gardner stayed awake for 11 days, slept 14 hours, stayed awake 24 hours, and slept 8 hours and was fine. (okay, sample size of 1. whatever.)

Hmm. The more I read, the more it looks like sleep debt accumulates until you get a chance to sleep it off, and a few days' worth of long sleep cures you. And it's frustratingly unknown what exactly the equation looks like. As for whether we all need the same amount of sleep or not, who knows?

Well, this has been pretty frustrating. Back to your regularly scheduled "actually learning actually useful things" another day, I guess.

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