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Wakefulness after Sleep Onset

Meaning

Wakefulness after sleep onset (WASO) is a key metric in sleep medicine that quantifies the total amount of time a person spends awake between the initial moment of falling asleep and the final awakening in the morning. High WASO values indicate fragmented or disturbed sleep maintenance, which is a common symptom of insomnia and various underlying medical conditions. Chronic elevation of WASO is clinically significant because it prevents the attainment of sufficient deep and REM sleep stages, thereby impairing cognitive function and disrupting nocturnal hormonal secretion patterns.