Sleep stages

Sleep cycles through non-REM and REM stages. Deep non-REM sleep is usually concentrated earlier, while REM periods tend to lengthen later. Brief awakenings can occur between cycles without meaning the night failed.

Stage percentages change with age, schedule, illness, substances, medication, and ordinary night-to-night variation. A single pie chart is not a personality test.

Clinical sleep staging uses brain waves, eye movements, muscle tone, breathing, and other signals. Consumer wearables usually infer stages from movement, heart rate, and related physiology. They can be useful for broad timing patterns but are less certain minute by minute.

Because algorithms differ, switching devices can create a new pattern even when your sleep has not meaningfully changed.

You cannot directly command more deep sleep tonight. Focus on enough sleep opportunity, a workable schedule, exercise, substance timing, and symptoms that may need evaluation. If the stage score itself is creating anxiety, hide it for a while.