Subjective sleepiness ratings (Epworth sleepiness scale) do not reflect the same parameter of sleepiness as objective sleepiness (maintenance of wakefulness test) in patients with narcolepsy

Objective: To evaluate whether subjective (Epworth Sleepiness Scale or ESS) and objective (Maintenance of Wakefulness Test or MWT) tests of sleepiness are equally useful in patients with narcolepsy. Methods: Correlational study evaluating the relationship between ESS and MW T as measures of sleepiness. Setting: Multi-center. Patients: 522 patients (17-68 year old men and women) with a current diagnosis of narcolepsy. Inte rventions: None. Results: Correlations were: MSLT and MWT, r = 0.52 (P < 0.001); MWT and ESS , I = - 0.29 (P < 0.001); MSLT and ESS, r = 0.27 (P < 0.001). Regression cu rve estimation using Linear and curvilinear models revealed no difference a mong linear and curvilinear models between MWT and MSLT, and between MSLT a nd ESS, However, curvilinear models were better at explaining the relations hip between MWT and ESS, with the cubic model being the best. As the level of severe sleepiness (as measured by the MWT) changed, the ESS remained sta ble. Conclusions: In a large narcolepsy sample, the MWT and ESS are not equally useful, and do not measure the same parameter of sleepiness. (C) 1999 Elsev ier Science Ireland Ltd. All rights reserved.