The Clinical Predictors of Sleepiness Correlated with the Multiple Sleep Latency Test in an Asian Singapore Population

STUDY OBJECTIVES: To explore the clinical predictors of sleepiness as objectively determined by the Multiple Sleep Latency Test with the Epworth Sleepiness Scale, age, body mass index, and overnight polysomnographic parameters at a tertiary referral center Sleep Disorders Unit. DESIGN: Retrospective, consecutive case series review. SETTING: A multidisciplinary sleep disorders unit in Singapore General Hospital, a tertiary-care university-affiliated hospital. PATIENTS: 72 consecutive patients evaluated for sleep disorders with overnight polysomnograms and Multiple Sleep Latency Tests between March 2002 and September 2002. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Mean sleep latency on the Multiple Sleep Latency Test was 9.0 +/- 4.4 minutes, and mean Epworth Sleepiness Scale score was 10.8 +/- 5.8. On univariate analysis, mean sleep latency on the Multiple Sleep Latency Test showed a significant negative correlation with the Epworth Sleepiness Scale score, apnea-hypopnea index, body mass index, arousal index, and time spent below 90% oxygen saturation during overnight polysomnography. After performing multiple linear regression, only Epworth Sleepiness Scale score and apnea-hypopnea index remained significantly correlated (P = .039 and P = .008, respectively). An Epworth Sleepiness Scale score of 8 or above predicted a mean sleep latency on the Multiple Sleep Latency Test of less than 10 minutes with a sensitivity of 73.9% and specificity of 50.0%. CONCLUSIONS: The Epworth Sleepiness Scale and apnea-hypopnea index are useful predictors of sleepiness in our Asian Singapore population.