Wake-Up Window

An essential part of waking up is to sleep well enough. However, if you feel groggy in the morning, it can also be something else entirely than having an insufficient amount of sleep. Just as falling asleep, waking up is more natural at some times more than the others. 

Sleep stages influence the easiness of waking up. All sleep stages go through 90-minute cycles. Each one of these sleep cycles includes a light sleep period, deeper sleep stages, and REM sleep. The deeper the sleep, the harder it is to wake up. Different stages occur in different ratios in each cycle, changing throughout the night. Deep sleep rules in the early night and REM sleep is the most prevailing the closer you get to the morning. 

Waking up is the easiest in between these 90 minutes cycles when you shift from REM sleep to light sleep. This so-called wake-up window is the most optimal time to wake up. Often this is the time when you wake up naturally. It is not unusual to wake up in the middle of REM sleep, but during deep sleep, you need a powerful outside irritant to make you wake up, such as an alarm clock. If you feel particularly tired or groggy immediately after opening your eyes, the chances are that you woke up during REM sleep. 

It’s not trivial to set up your alarm to the exact time when your sleep cycles are shifting since sleep cycle lengths and needs are highly individual. In practice, the cycles are not precise, and they can be disturbed by waking up in the middle of the night (that you don’t necessarily remember). There are some alarm clocks out in the market that are marketed as being able the detect the most optimal timing to wake up. Currently, however, no tracker on the consumer market can truly detect the sleep stages correctly.

Example Habits to try:

Additional Reading


Partonen, T. (2014). Lisää unta – Kiireen lyhyt historia. Helsinki: Duodecim.

Walker, M. (2017). Why we sleep: Unlocking the power of sleep and dreams. Simon and Schuster.