Circadian Health Glossary
Sleep Inertia
Sleep inertia is the grogginess and reduced alertness experienced immediately after waking. It typically lasts for a few minutes to an hour and is caused by the brain transitioning from sleep to full wakefulness.
What Causes Sleep Inertia?
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Waking from Deep Sleep: Occurs most strongly when waking from slow-wave (deep) sleep.
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Circadian Timing: Can be worse when waking during a low-energy period in the circadian cycle, or the body’s biological night, such as early morning hours for late chronotypes (night owls).
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Sleep Deprivation: Insufficient sleep increases the intensity and duration of sleep inertia.
Why Is Sleep Inertia Important?
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Performance Impact: Reduces cognitive function, decision-making, and reaction time immediately after waking.
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Safety Concerns: Can pose risks for tasks requiring alertness, such as driving or operating machinery.
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Management: Strategies like light exposure, physical activity, or caffeine can help reduce its effects.