Brain Advance Access originally published online on April 5, 2006
Brain 2006 129(6):1609-1623; doi:10.1093/brain/awl079
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Correlates of sleep-onset REM periods during the Multiple Sleep Latency Test in community adults
1 Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine Palo Alto, CA, USA 2 Howard Hughes Medical Institute Stanford, CA, USA 3 Department of Population Health Sciences, University of Wisconsin-Madison Madison, WI, USA
Correspondence to: Emmanuel Mignot, Stanford University Center for Narcolepsy, 701 Welch Road, B145, Palo Alto, CA 94304-5742, USA E-mail: mignot{at}stanford.edu
The diagnosis of narcolepsy without documented cataplexy is based on the observation of two or more sleep-onset REM periods (SOREMPs) during the Multiple Sleep Latency Test (MSLT). We report on the prevalence and correlates of SOREMPs in the community-based Wisconsin Sleep Cohort Study. MSLTs were conducted following nocturnal polysomnography (NPSG) and daily sleep diaries in 289 males and 267 females (age 35–70, 97% Caucasians). Multiple SOREMPs were observed in 13.1% of males and 5.6% of females. An MSLT mean sleep latency 
8 min and 
2 SOREMPs (diagnostic of narcolepsy) was observed in 5.9% (males) and 1.1% (females), all without cataplexy. Because of significant sex interactions, analyses were stratified by sex. Increased prevalence of HLA-DQB1*0602, a marker of narcolepsy, was observed in males but not in females with 2 SOREMPs. Males with multiple SOREMPs compared with those with no SOREMPs had shorter rapid eye movement (REM) latency during NPSG, were sleepier on the MSLT and reported increased sleepiness, hypnagogic hallucinations and cataplexy-like symptoms, suggesting a narcolepsy-like phenotype. In males only, the occurrence of SOREMPs increased with shift work and some indirect markers of sleep restriction, such as shorter sleep a day before NPSG. SOREMPs were unrelated to age, body mass index, depression (Zung Scale), anxiety (State-Trait Anxiety Scale) and the number of apnea and hypopnea events per hour of sleep (AHI), but were associated with decreased mean lowest oxygen saturation in males. Finally, we found that both males and females with SOREMPs reported taking more antidepressants, but those were of the types known not to suppress REM sleep. These results suggest a high prevalence of narcolepsy without cataplexy, as defined by the International Classification of Sleep Disorders, and/or a large number of false-positives for the MSLT.
Key Words: HLA; DQB1*0602; sleep-onset REM period; MSLT; narcolepsy
Abbreviations: AHI, apnea–hypopnea index; BMI, body mass index; EDS, excessive daytime sleepiness; EPW, Epworth sleepiness scale; HH, hypnagogic hallucinations; ICSD-2, International Classification of Sleep Disorders (revised, 2005); MSL, mean sleep latency; MSLT, Multiple Sleep Latency Test; NPSG, nocturnal polysomnography; PLM, period leg movement; PSG, polysomnography; REM, rapid eye movement; SOREMPs, sleep-onset REM sleep periods; SP, sleep paralysis; SDB, sleep disordered breathing; TST, total sleep time; WSC, Wisconsin Sleep Cohort Study
Received December 25, 2005. Revised March 8, 2006. Accepted March 9, 2006.
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