There's an old folk saying that goes like "He got out of bed on a wrong foot" - to indicate that the person's day is going poorly because of the way that person woke up.

Is it is possible for a human to disrupt the awakening process, causing negative cognitive side effects for the rest of the day? If so, how long does it take to restore normal cognition?

There's this related question that I asked - if different parts of a human brain can be asleep independently of each other? This question is a variation on that one, and specifically deals with the process of awakening or activating brain regions in the morning.

I'm aware of the concept of "Sleep inertia". However, it does not seem to be the phenomenon in question, as sleep inertia is frequently mentioned in the context of napping. (where napping over a certain time leads to sleep inertia). Additionally, sleep inertia has been described in terms of decline of motor activity, and not as cognitive side effects lasting for a whole day.

From personal experience, it seems that I'm doing best if I get out of bed immediately following a natural awakening, even if it is rather early, as opposed to snoozing for another 30-40 minutes.

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    $\begingroup$ I want so badly a response to that... $\endgroup$ Mar 30, 2015 at 1:59
  • $\begingroup$ I think the "sleep inertia" you refer to is the reason - if you are woken by your alarm during a particular cycle of sleep this would have an effect lasting all day [haven't looked this up - anecdotal]. This would then be referred to as having woken up on the wrong side of the bed (which is just a saying not a literal reason why you are having an off day). Could be due to all sorts of reasons though, including nutrition, recent physical activity, stress, alcohol/drug consumption... etc! $\endgroup$
    – Luke
    Apr 2, 2015 at 13:33
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    $\begingroup$ I'd say anytime a human hasn't slept enough, of course how much is enough sleep depends on the individual. $\endgroup$
    – vajra78
    Apr 3, 2015 at 0:42
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    $\begingroup$ Isn't sleep paralysis another kind of disrupted sleep phenomenon? $\endgroup$ Apr 3, 2015 at 9:54

2 Answers 2


I did a quick search and found some research in this area. Sleep inertia is the technical term for feeling groggy for a while after waking up.

In a review article by Patricia Tassi, Alain Muzet (Sleep inertia. Sleep Medicine Reviews. Volume 4, Issue 4, August 2000, Pages 341–353), they define sleep inertia as

Sleep inertia is a transitional state of lowered arousal occurring immediately after awakening from sleep and producing a temporary decrement in subsequent performance.

and also says,

Depending on the studies, it [sleep inertia] can last from 1 min to 4 h. However, in the absence of major sleep deprivation, the duration of sleep inertia rarely exceeds 30 min.

Same article reviews several studies (first report in 1964) on sleep inertia relating to sleep stages:

Abrupt awakening during a slow wave sleep (SWS) episode produces more sleep inertia than awakening in stage 1 or 2, REM sleep being intermediate.

So yes, sleep stage seems to correlate with "waking up in the wrong way" as @CactusWoman suggested.

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    $\begingroup$ Good find, I especially appreciate the up to 4 hour timing information. This may also interact with caffeine, which is frequently consumed in the morning. Apparently caffine half-life is about 5.7 hours (caffeineinformer.com/the-half-life-of-caffeine) $\endgroup$
    – Alex Stone
    Apr 2, 2015 at 18:53

Sleep occurs in stages. There are three stages of non-REM sleep followed by REM sleep. Natural waking occurs during the REM stage. If your alarm goes off while you are in the middle of deep sleep, you are going to feel different from if you had woken up naturally. That's why there's a market for alarm clocks designed to wake you up during light sleep.

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    $\begingroup$ do you have references for this "feel different" claim? $\endgroup$
    – Memming
    Apr 2, 2015 at 15:37
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    $\begingroup$ I have an "alarm clock" which is silent but slowly brightens a lamp over the course of a half hour or so. It is called the Sunrise Clock, I got it about 20 years ago. Normally I awaken a few minutes before it goes "click" and begins to come on. If I set an actual alarm, I wake up about 1 minute before. $\endgroup$
    – user17124
    Oct 24, 2015 at 14:03

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