Sleep Cycle: Understanding Sleep Stages for Better Recovery

Your night is not a long, calm river. It is made up of sleep cycles of approximately 90 minutes, which repeat 4 to 6 times depending on the total duration of your nights. Each cycle consists of different sleep phases, and understanding their role transforms your approach to recovery. Understanding them can help you achieve better sleep.

Deciphering Sleep Phases

Light Sleep: The Gateway

Light sleep accounts for approximately 50% of your night. It corresponds to phases N1 (falling asleep) and N2 (confirmed sleep). During this phase, the body begins to relax, temperature drops, and the brain produces characteristic sleep spindles. This is the phase you exit most easily; a slight disturbance is enough to wake you up.

Light sleep plays a role in consolidating procedural memory (know-how, actions) and prepares for transitions to deeper phases.

Deep Sleep: King of Physical Recovery

Phase N3, or slow-wave deep sleep, is when the body performs its reconstruction work: cell repair, protein synthesis, immune system strengthening, and a peak in growth hormone secretion. This is also where declarative memory (facts, events) is consolidated.

It is more abundant at the beginning of the night, with the first two or three cycles containing more of it. Going to bed late directly compresses this phase, with direct consequences on physical recovery and metabolic health.

REM Sleep: Nocturnal Emotional Intelligence

REM sleep (Rapid Eye Movement), or paradoxical sleep, is the dream phase. The brain is as active as when awake, but the body is temporarily paralyzed. This is the time for processing emotions, consolidating long-term memory, and maintaining neuroplasticity.

REM sleep gradually lengthens throughout the night; it is much more present in the later cycles, between 5 am and 8 am. Cutting your night short deprives the brain of this essential phase for emotional balance.

How many cycles per night?

An optimal night contains 5 complete 90-minute cycles, or about 7.5 hours of sleep. Most adults function between 4 and 6 cycles. The key is to wake up naturally at the end of a cycle, not in the middle, which explains why some awakenings are abrupt (mid-cycle) and others easy (end-of-cycle). Sleep tracking apps or progressive alarms try to detect these transitions to optimize wake-up time.

What disturbs your cycles

• Alcohol: fragments REM cycles in the second part of the night
• Screens: delay falling asleep and reduce initial deep sleep
• Heat: a room above 20°C (68°F) disturbs transitions between phases
• Light: even dim light inhibits melatonin and alters REM sleep
• Stress: increases micro-awakenings between cycles

Total darkness is one of the most powerful levers for preserving the integrity of your cycles. Our mulberry silk sleep mask ensures this complete darkness, even in environments you don't control, such as hotel rooms, travel, or cohabitation.