Selim R. Benbadis, Michael Perry, Barbara R. Wolgamuth, John Turnbull and Wallace B. Mendelson. Cleveland Clinic Foundation Sleep Disorders Center, ...
Sleep, 18(S}:342-345 © 1995 American Sleep Disorders Association and Sleep Research Society
Daytime Sleepiness Mean Versus Median for the Multiple Sleep Latency Test Selim R. Benbadis, Michael Perry, Barbara R. Wolgamuth, John Turnbull and Wallace B. Mendelson Cleveland Clinic Foundation Sleep Disorders Center, Department of Neurology, Cleveland, Ohio, U.S.A.
Summary: Since its introduction in the mid-1970s, the mUltiple sleep latency test (MSLT) has become the standard method for evaluating hypersomnolence. The mean sleep latency is usually calculated and constitutes the traditional basis for interpretation. Mean and median are both measures of the central tendency of a distribution, but because the trials of the MSLT are limited to 20 minutes, the median may be more appropriate. The objective of this study was to compare the value of the mean versus the median sleep latency in the interpretation of the MSLT. We retrospectively analyzed 100 MSLTs performed for evaluation of excessive daytime sleepiness. Patients' ages ranged from 6 to 84 years (mean 43). Mean and median sleep latencies were calculated according to standard formulas. We classified each record into one of three categories, using both the mean and the median sleep latencies: normal (> 10 minutes), moderate (205 and ~ 10 minutes), and severe sleepiness «5 minutes). Of the 100 MSLTs, 89 remained in the same category (normal, moderate, severe) whether mean or median was used. In II cases, the category changed. All shifts were by one category, that is, no shift occurred between normal and severe. This study suggests that, despite valid theoretical arguments for the use of the median, both measures are equally acceptable for clinical purposes. Key Words: MSLT -Daytime sleepiness-Central tendency-Mean. Resume: Depuis son introduction par l'ecole califomienne, Ie test de latence multiple de sommeil (TLMS) est devenu la methode de reterence dans Ie bilan des etats d'hypersomnolence. En general, la moyenne des latences d'endormissement est calculee, et constitue la base de l'interpretation. La moyenne et la mCdiane mesurent la tendance centrale d'une distribution, mais du fait que les siestes du TLMS sont limitees a 20 minutes, la mCdiane peut sembler plus adequate. Le but de ce travail etait de com parer la valeur de la moyenne et de la mCdiane dans l'interpretation du TLMS. Nous avons etudie de fa, 10 minutes, moderate (M) if 2: 5 and $10 minutes and severe (S) if < 5 minutes. Each record was therefore assigned two classifications: one using the mean, and one using the median. If there was a discrepancy between the two classifications, patients' charts were reviewed to gather relevant history.
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