Objective: We aimed to examine the relationship between subjective and objective sleepiness in obstructive sleep apnea syndrome (OSAS) patients with residual sleepiness, and to determine whether baseline objective sleepiness severity predicts the response to modafinil therapy.
Methods: Data were obtained from a randomized, placebo-controlled modafinil (200 mg/day) study in Japanese OSAS patients with residual sleepiness receiving nasal continuous positive pressure (n-CPAP) treatment. We analyzed 50 participants whose subjective (Epworth Sleepiness Scale [ESS] total score) and objective (Maintenance of Wakefulness Test [MWT] sleep latency) sleepiness were evaluated before and after treatment. Subjects were dichotomized into two subgroups according to the mean baseline MWT sleep latency. ESS total score and MWT sleep latency changes after treatment were compared between the placebo and modafinil groups in both subgroups.
Results: The mean baseline ESS total score and MWT sleep latency were 14.1 ± 2.8 and 14.2 ± 4.9 min, respectively; there was no significant correlation between these two variables. Patient characteristics were similar between the two subgroups (MWT sleep latency: <14 min, n = 23; ≥14 min, n = 27). In the <14-min subgroup, changes in ESS total score and MWT sleep latency after treatment were significantly greater in the modafinil group than in the placebo group (p = 0.005). In the ≥14-min subgroup, changes in these parameters did not differ between the treatment groups.
Conclusion: In OSAS patients with residual sleepiness, the objective sleepiness level was not as high as expected, despite increased subjective sleepiness. Improvements in subjective and objective sleepiness seemed difficult to achieve with modafinil treatment among subjects with less objective sleepiness.
Keywords: Epworth Sleepiness Scale; Maintenance of Wakefulness Test; Modafinil; Nasal continuous positive airway pressure; Obstructive sleep apnea syndrome; Residual sleepiness.
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