What is sleep inertia and why is it so hard for us to wake up?

Surely the phrase “I can’t get up today” crossed your mind at some point just when the alarm clock starts ringing, as the song of Mecano, the mythical Spanish pop group of the 80s, said. — one of those machines that we inevitably got used to obey. And yes, we do, but for a while we are sleepy, disoriented, and our cognitive abilities, shall we say, are significantly reduced. This common phenomenon is known in the scientific literature as sleep inertiaand a third process in the regulation of rest.

The two processes traditionally responsible for regulating when we are more likely to fall asleep are circadian And homeostatic. The first is like a clock that marks the best time to start sleeping; and second, a kind of hourglass, or a compound called adenosine, which measures how many hours we’ve been awake.

For our sleep to occur without difficulty, both processes must participate in a kind of coordinated dance, so that the most suitable time for sleep also coincides with the moment when adenosine accumulated during wakefulness is optimal.

Well, there are those who consider sleep inertia to be the third process in this regulation. It will act immediately upon awakening in the morning, counteracting the low probability of sleep that is characteristic of the homeostatic process and the high probability of being awake that is indicated by the circadian process.

What happens half an hour after we wake up?

Although the process of awakening is less understood than the process of falling asleep, the truth is that some data on neural activity show that the brain remains in a more sleep-like state when we have just opened our eyes than before we fell asleep. In addition, it is also known that cerebral blood flow during the transition from sleep to wakefulness is slower than immediately before we entered the arms of Morpheus.

Thus, it seems that we have a physiological basis for having a hard time getting on our feet every morning. And will it have any advantage in terms of evolution? We might think that in nature, if something wakes us up, it would probably be better if we got up and ran in a split second. However, given the complexity of the neural mechanisms involved in the transition between sleep and wakefulness, one hypothesis is that sleep inertia could protect this process by avoiding abrupt transitions.

On the other hand, this inertia means that when we wake up at night, it’s usually easy to get back to sleep. Another hypothesis for the benefit of gradual awakening is to avoid the intrusion of dreams into wakefulness in the form of hallucinations in the event of awakening in the middle of REM sleep.

While this is considered normal, there are factors that can increase this trance. For example, if we do not get enough sleep at night and wake up earlier than our body needs, this increases the inertia of sleep. The same thing happens if we are lagging behind a chronic sleep deficit.

The time of the day or night at which the awakening occurs also affects: the inertia of sleep is greater when we wake up in our biological night, when the body understands that it is still time to sleep. And does the phase of sleep we are in affect? In this case, some contradiction arises: it is not clear whether there is more inertia upon awakening in deeper phases or not.

How does sleep inertia affect us and how can we reduce it?

This boot failure affects various aspects of cognitive performance, but at what level? On the one hand, there are studies that have found an effect only on the reaction rate. Others also indicate that accuracy will be reduced.

In any case, performing complex tasks that require increased attention will suffer the most from sleep inertia. For this reason, it would be wise to perform activities that require memory, counting, decision making, or psychomotor coordination after these first 30 minutes of wakefulness.

As an illustration, a retrospective analysis of more than 400 US Air Force accidents showed that those that were associated with human factors most often occurred in the first hour after waking up. Intuitively, sleep inertia can create problems for emergency responders such as medical personnel or firefighters.

While sometimes unavoidable, there are things we can do to make it easier for us to wake up. On the one hand, we know that little sleep increases inertia. We also know that if we wake up during our biological night, it will also take longer to start. Therefore, if you get enough sleep every night and do it at the right time, you can reduce this inertia. And if we want to reduce the inertia of daytime sleep, then the shorter it is (always less than 30 minutes), the less it will cost us to restore performance.

In the case of staff on duty, although bright light upon awakening increases subjective vigilance, no positive effect on objectively assessed performance was found. It seems that sound and music can effectively reduce sleep inertia.

Based on what we know about thermoregulation and sleep, chilling the limbs can also wake us up, although this has not been proven at this time. And while exercising upon waking appears to increase alertness, it has also not been proven to improve subsequent performance. Caffeine may work if we take it before bed, but this is not recommended.

In short: to reduce the effects of day-to-day sleep inertia, try to get enough sleep every night. And if they have a difficult and important task to complete, it shouldn’t be the first thing they do after the alarm goes off.