About 90min Sleep Cycle

As you turn the Time-picker dial to set your sleep time, you’ll notice that certain time periods are round-framed. This indicates a time frame that aligns with the ’90-minute cycle’ (±10 minutes).

Medically, people sleep in cycles ranging from 60 to 120 minutes, with 90 minutes being the average most commonly observed.

During each cycle, there is a pattern of alternating NREM (Non-REM, Light and Deep sleep stages) and REM (Rapid Eye Movement) sleep stages.

As the graph below, during sleep, there is a repeating cycle every 90 minutes of NREM and REM sleep stages, along with brainwave patterns.

Medically, a healthy ‘Sleep Wave pattern’ is described as having longer ‘Deep Sleep’ at the beginning of the sleep time, and then longer ‘REM sleep’ towards the end.


Based on this ’90-minute cycle’, Zalza incorporates brainwave entrainment frequencies that match the healthy ‘Sleep Wave pattern’ into all our sleep musics.

Therefore, we recommend you to adjust your sleep time to align with this ’90-minute’ cycle for better sleep!