Chest
Volume 102, Issue 3, September 1992, Pages 699-703
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Clinical Investigations
Disorders of Excessive Sleepiness: Treatment Improves Ability to Stay Awake But Does Not Reduce Sleepiness

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A total of 47 patients with sleep disorder (36 male and 11 female) with a mean age of 47.5 ± 15 years were evaluated for daytime symptoms with a Multiple Sleep Latency Test (MSLT) and a Maintenance of Wakefulness Test (MWT) given on the same day—once at the time of their diagnostic evaluation and again after one to six months of treatment. The MSLT and MWT data are consistent with the notion that sleep tendency, as measured by the MSLT and ability to remain awake, as measured by the MWT, represent different physiologic processes. Data show a marked treatment-related improvement in ability to stay awake as measured by the MWT and no treatment-related improvement in sleepiness as measured by the MSLT. We conclude that there is a heterogeneous subpopulation of patients with sleep disorders whose symptoms of daytime sleepiness will show no treatment-related improvement in daytime symptoms if they are evaluated only by the MSLT. We suggest that, since ability to stay awake (and not ability to fall asleep) is a requisite for all job-related duties, an objective, physiologically based test such as the MWT should be used to assess the impact of sleep disorders in cases where there is a clinical concern about fitness to drive or work.

Section snippets

Methods

We studied a total of 47 patients (36 male and 11 female) with a mean age of 47.5 ± 15 years that included patients with the following diagnosis: 27 with obstructive sleep apnea, seven with narcolepsy, seven with idiopathic hypersomnia, one with head trauma, four with depression, and one with periodic leg movement during sleep. Diagnostic criteria were as described by the Association of Sleep Disorders Centers.4 All patients were free of medications that significantly affected the central

Results

Figure 1 shows box plots that summarize the distributions for the MSLT tests administered before and after treatment. Box plots are useful ways to present truncated data sets such as those resulting when individual scores frequently reach a protocol-dependent maximum such as 20 min for the MSLT and 40 min for the MWT. Each box encompasses the middle 50 percent of the distribution and the horizontal line within the box represents the median. The notches about the horizontal line denote the 95

Discussion

Our data clearly indicate that for a heterogeneous sample of patients with the clinical question of excessive daytime sleepiness and for a homogeneous subsample of patients with obstructive sleep apnea, the MWT is sensitive to changes in ability to remain awake that result from therapeutic maneuvers. The MSLT, however, did not change with therapy. The treatment-related changes in MWT sleep latencies are comparable in magnitude to those observed by Poceta et al6 in 322 patients with sleep apnea

ACKNOWLEDGMENT

Barbara Bigby assisted with manuscript preparation.

References (13)

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Primary funding and support for this project came from the Sleep Disorders Institute of Troy, Mich. Dr. Mitler is supported by Public Health Service grants, RO1 NS20459 and R03 AA08235 and by Clinical Research Center grant RR00833 to Scripps Clinic and Research Foundation and by a grant from the American Narcolepsy Association.

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