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The Epworth Sleepiness Scale may not reflect objective measures
of sleepiness or sleep apnea
Ronald D. Chervin, MD, MS and Michael S. Aldrich, MD
From the Sleep Disorders Center and Department of Neurology, University
of Michigan, Ann Arbor, MI.
OBJECTIVE: To assess the validity of the Epworth
Sleepiness Scale score (ES) as a measure of sleepiness among patients
suspected or confirmed to have obstructive sleep apnea syndrome.
BACKGROUND: The ES is used with increasing frequency
as a measure of excessive daytime sleepiness in part because several
studies suggested that the ES correlates with mean sleep latency (MSL)
on the Multiple Sleep Latency Test and with severity of sleep apnea
among patients with that disorder. However, associations identified
between the ES and other measures were not strong or consistent.
METHODS: The authors used regression models and
retrospective data from a relatively large series of 237 patients
to restudy how ES relates to MSL, to a simple self-rating of problem
sleepiness (available for 141 patients), and to two polysomnographic
measures of sleep apnea severity: the number of apneas or hypopneas
per hour of sleep and the minimum recorded oxygen saturation.
RESULTS: The ES had a statistically significant
association with self-rated problem sleepiness but not with MSL or
measures of sleep apnea severity. Male gender, adjusted for potential
confounding variables, had considerably more influence on the ES than
did MSL or measures of sleep apnea severity.
CONCLUSIONS: Our data suggest that the subjectively
derived ES cannot be used as a surrogate for the objectively determined
MSL.
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