Why do I feel groggy in the morning?
Morning grogginess is sleep inertia — a normal physiological transition out of sleep. Its severity depends on which sleep stage your alarm interrupted, your total sleep time, and your circadian timing.
The stage of waking
If your alarm fires during N3 deep sleep, you will feel much worse than if it fires during light N2 or REM. Trotti (2017) calls this the dominant determinant of inertia severity.
Sleep debt
Chronic short sleep amplifies inertia. CDC data show 1 in 3 adults sleep fewer than 7 hours per night — they pay for it in worse mornings.
Circadian alignment
Waking against your natural chronotype (e.g., a night-owl forced to rise at 6 AM) magnifies inertia regardless of total sleep.
Sources
- Trotti, Nature and Science of Sleep, 2017. Sleep inertia: current insights
- Centers for Disease Control and Prevention. CDC — Sleep and Sleep Disorders
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