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J Psychiatr Res. 2012 Apr;46(4):422-7. doi: 10.1016/j.jpsychires.2011.06.008. Epub 2012 Jan 31.

Determining the level of sleepiness in the American population and its correlates.

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Stanford Sleep Epidemiology Research Center, Stanford University, School of Medicine, 3430 W. Bayshore Road, Palo Alto, CA 94303, USA.



To assess the prevalence, to determine the risk factors and to evaluate the impacts of excessive sleepiness in the general population.


It is a cross-sectional telephone study using a representative sample consisting of 8937 non-institutionalized individuals aged 18 or over living in Texas, New York and California. They represented a total of 62.8 million inhabitants. The participation rate was 85.6% in California, 81.3% in New York and 83.2% in Texas. Interviews were managed by the Sleep-EVAL expert system. The questionnaire included questions on sleeping habits, life habits, health, DSM-IV mental disorders, DSM-IV and ICSD sleep disorders.


As many as 19.5% of the sample reported having moderate excessive sleepiness and 11.0% reported severe excessive sleepiness. Moderate excessive sleepiness was comparable between men and women but severe excessive sleepiness was higher in women (8.6% vs. 13.0%). Factors associated with moderate excessive sleepiness were sleeping 6 h or less per main sleep episode (OR:2.0); OSAS (OR:2.0); insomnia disorder (OR:2.4); Restless Legs Syndrome (OR: 1.8) major depressive disorder (OR: 1.7); anxiety disorder (OR:1.5) and use of tricyclic antidepressant (OR: 2.1) presence of heart disease (OR: 1.5), cancer (1.8) and chronic pain (1.3). Factors associated with severe excessive sleepiness were similar with the addition of being a woman (OR:1.5), alcohol dependence (OR: 1.4), bipolar disorder (OR: 2.1), use of over-the-counter sleeping pills (OR: 2.5), narcotic analgesics (OR: 3.4), Antidepressants (other than SSRI or tricyclic) and presence of gastro-esophageal reflux disease (OR:1.6). Sleepy individuals were twice as likely than non-sleepy participants to have had accidents while they were at the wheel of a vehicle during the previous year.


Excessive sleepiness is highly prevalent in the American population. It was strongly associated with insufficient sleep and various sleep disorders as well as mental and organic diseases.

[Indexed for MEDLINE]

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