Wake-Up Window

Pietari Nurmi
Jul 11 · 3 min read

Obviously, the most important part of waking up refreshed is to get enough good quality sleep. However, sleeping too little is hardly the only reason for feeling groggy and tired in the morning. Like falling asleep, waking up, too, happens more naturally at specific times and gets more challenging at others.

The ongoing sleep stage has a significant effect on the easiness of waking up. All sleep stages progress in 90-minute cycles throughout the night. Each of these sleep cycles includes light, deep, and REM stages. The deeper the sleep stage, the harder it is to wake up. The ratios between different stages in the cycles change 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, either. However, during deep sleep, a powerful outside distraction (such as an alarm clock) is needed to make you wake up. If you feel particularly tired or groggy immediately after opening your eyes, the chances are that you woke up at a non-optimal stage of the sleep cycle. Maybe something just dragged you out of deep sleep?

It’s not trivial to set up your alarm to the exact time when your sleep cycles are shifting since sleep cycle lengths are highly individual, and the required amount of sleep is personal. If we had a hypothetical person known to have precisely 90-minute sleep cycles, that person might be able to hit the optimal wake-up window by trying to fall asleep exactly 7.5 hours before the alarm. However, in practice, the cycles are never that precise and can be disturbed, for example, by nightly awakenings (that you don’t necessarily remember). There are some alarm clocks out there marketed as being able to detect the most optimal time to wake up. Beware, though: none of the trackers currently on the consumer market can detect sleep stages accurately enough to make reliable assumptions of your optimal wake-up time.

Habits From This Lesson

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.