Using population-based data, we document the comorbidities (medical, neurologic, and psychiatric) and consequences for daily functioning of excessive quantity of sleep (EQS), defined as a main sleep period or 24-hour sleep duration ≥9 hours accompanied by complaints of impaired functioning or distress due to excessive sleep, and its links to excessive sleepiness.


A cross-sectional telephone study using a representative sample of 19,136 noninstitutionalized individuals living in the United States, aged ≥18 years (participation rate = 83.2%). The Sleep-EVAL expert system administered questions on life and sleeping habits; health; and sleep, mental, and organic disorders (Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision; International Classification of Sleep Disorders: Diagnostic and Coding Manual II, International Classification of Diseases and Related Health Problems, 10th edition).


Sleeping at least 9 hours per 24-hour period was reported by 8.4% (95% confidence interval = 8.0–8.8%) of participants; EQS (prolonged sleep episode with distress/impairment) was observed in 1.6% (1.4–1.8%) of the sample. The likelihood of EQS was 3 to 12× higher among individuals with a mood disorder. EQS individuals were 2 to 4× more likely to report poor quality of life than non-EQS individuals as well as interference with socioprofessional activities and relationships. Although between 33 and 66% of individuals with prolonged sleep perceived it as a major problem, only 6.3 to 27.5% of them reported having sought medical attention.


EQS is widespread in the general population, co-occurring with a broad spectrum of sleep, medical, neurologic, and psychiatric disorders. Therefore, physicians must recognize EQS as a mixed clinical entity indicating careful assessment and specific treatment planning. ANN NEUROL 2013;73:785–794