Prevalence and Clinical Correlates of a Short Onset REM Period (SOREMP) during Routine PSG.

STUDY
OBJECTIVES: The objectives of this study were to quantify the (1) sensitivity and specificity of nocturnal PSG SOREMP (REM latency ≤ 15 min) for narcolepsy in those being evaluated for hypersomnolence and (2) prevalence and predictors of SOREMP during baseline PSG for patients being evaluated for various sleep disorders.
DESIGN: This was a retrospective analysis of a large repository of de-identified PSG and MSLT test results from 2007 to 2013. SETTING AND PATIENTS: Patient records were retrieved from a repository of studies completed at a variety of sleep laboratories across the USA. Included in the analyses were 79,651 general sleep clinic patients (without an MSLT; 48% male; 72% Caucasian) and an additional 3,059 patients (31.3% male; 72% Caucasian) being evaluated for hypersomnolence (with a consecutive MSLT).
INTERVENTIONS: NA. MEASUREMENTS AND
RESULTS: For patients being evaluated for hypersomnolence, the prevalence of PSG SOREMP increased in a dose-response fashion with the number of REM onsets that occurred on a consecutive MSLT (0.5% for no MSLT SOREMPs to > 33.0% for those with 5 MSLT SOREMPs). Overall, having a PSG SOREMP was highly specific (99.5%; 95% CI: 99.1-99.7%) but not sensitive (6.7%; 95% CI: 4.7-9.2%) for narcolepsy. The prevalence of PSG SOREMP for patients in the general sleep clinic sample (i.e., not being evaluated by a consecutive MSLT) was 0.8% and was much higher in those that work night/swing shift. In adjusted models, African American race contributed to the most variance in PSG SOREMP.
CONCLUSIONS: A short onset rapid eye movement (REM) latency occurs rarely in general sleep clinic samples (< 1.0%), but is highly specific for the diagnosis of narcolepsy. Although rare, the prevalence of the phenomenon is much higher than the estimated prevalence of narcolepsy and may provide a critical opportunity for practitioners to identify narcolepsy in sleep clinic patients. These data also suggest that the utility of polysomnography (PSG) short onset REM peroid (SOREMP) for the diagnosis of narcolepsy may be altered by a history of shift/night work and/ or other factors that may allow for a rebound of REM sleep (e.g., undergoing a positive airway pressure titration), supporting published guidelines that other sleep disorders and insufficient and/or poorly timed sleep should be ruled out and/or adequately controlled for prior to conducting sleep testing. Further research is needed to understand racial differences in PSG SOREMP and narcolepsy. This study was limited in that data on cataplexy (with exception to that in final diagnosis) and habitual sleep duration were not available.