What’s the Ideal Length for a Nap?

It’s the afternoon, you’ve just finished lunch, and now you’re struggling to stay awake. Is a nap a good idea, or can it actually make you feel worse?

What is the ideal length for a nap ? According to researchers, it depends.

In most cases, researchers agree that taking a short 10 to 30-minute nap can make you feel better, but a longer nap may actually make you feel worse. To understand why, we first need to understand two key terms – sleep inertia and slow-wave sleep.

Sleep inertia is that groggy feeling you sometimes experience when you first wake up after a long sleep. During sleep inertia, part of your body is actually still in sleep mode, which makes it difficult to perform even basic tasks. Sleep inertia generally lasts 30 minutes or less – although it can last longer in people who are either sleep deprived or who nap too long. In most cases, the adrenaline rush from waking up to a loud alarm clock, or the caffeine from a morning cup of coffee can help knock you out of the sleep inertia state.

Slow-wave sleep (SWS) is the scientific term for deep sleep. This is the time when you get the most rest, and your body restores itself. Short-wave sleep is the hardest to wake up from, however.

The key to a helpful nap is either waking up before sleep inertia hits or sleeping past that short-wave sleep cycle.

Sleep Inertia and the Brain

Recent brain scan research published in NeuroImage used EEG, fMRI, and behavioral measurements to study brainwave patterns during a 45-minute nap. Participants were given a mental subtraction task before their nap, then immediately after. Those who were in a deeper sleep when awakened tended to have the biggest drop in performance from the pre-sleep test to the post-sleep test.

The EEGs found that those who had the biggest drop in performance had shown the most delta brainwave activity (i.e., slow-wave sleep). The researchers also found that the functional connectivity between different brainwaves was strongly disrupted right after waking up from the nap, another reason for sleep inertia.

Sleep inertia hits at different times for different people, but in general, 30 minutes is the maximum you want to sleep if you’re taking a short nap. That is enough time to wake up feeling refreshed, and get the benefits of napping like improved performance, alertness, and mood. Otherwise, it takes awhile to wake up. This may not be a big deal in most situations, but it’s very important in situations that involve driving or performing potentially dangerous tasks right after a nap. Sleeping too long can interfere with the ability for your brain to properly function.

Ideal length of Nap

If you have the option of taking a longer nap, 90 minutes is optimal. This gives your body enough time to make it through a complete sleep cycle – going from the lightest to the deepest stage and back again. Not only will you wake up feeling refreshed, it has been found to boost creativity and memory.