Why do I wake up tired even after sleeping for a long time?
Waking up tired despite sleeping for a long time is a normal phenomenon called sleep inertia, and the time of waking and evening screen use play a clear role in it. Limit screens before bedtime and keep naps short (around 30 minutes) to avoid the worst grogginess.
Waking up tired despite having slept for a long time has a name: sleep inertia. This is the period of grogginess and sluggishness immediately after waking up. Cognitive functions, such as thinking and reacting, largely recover within 30 minutes. Your motor skills, meaning how you move and coordinate, can remain below your normal level for more than 75 minutes.
The time at which you wake up makes a big difference. Waking up early in the morning produces more sleep inertia than waking up later in the day, even if you have slept for enough hours. So it is not just about the amount of sleep, but also about when your body is pulled out of sleep.
Evening screen use (phone, TV, tablet) is associated with greater sleep inertia the following morning and more fatigue during the day. This is an associative relationship that has not yet been fully proven as a direct cause, but the association is statistically clearly present.
After nights with little or poor sleep, for example due to a night shift, sleep inertia is stronger and can persist for up to an hour after getting up. A long nap of 90 minutes during the day can also produce this effect, because you then enter deep sleep stages from which it is harder to wake up. A short nap of 30 minutes causes far less of that groggy feeling.
If you want to use naps, keep them short. A nap of around 30 minutes reduces fatigue and improves alertness, without leaving you wandering around feeling drowsy for a quarter of an hour afterwards. The benefits of a strategically short nap outweigh the brief sleep inertia that comes with it.
Based on multiple studies of moderate quality of evidence. Most findings come from laboratory research or observational studies; large randomised trials on sleep inertia are scarce. The screen use association is associative, not causally proven.