these articles presented new, useful information, they used almost exclusively the latency of the first sleep stage in the recording for the quantitative evaluation of ...
Sleep, 1)(1):243-245 © 1986 Raven Press, New Yark
An Alternative to the Multiple Sleep Latency Test for Determining Sleepiness in Narcolepsy and Hypersomnia: Polygraphic Score of Sleepiness Bednch Roth, Sona Nevsfmalova, Karel Sonka, and Petr Docekal Department of Neurology, Charles University Medical Faculty, Prague, Czechoslovakia
Summary: This article describes a quantitative assessment of pathological diurnal sleepiness in three groups of patients with excessive daytime sleepiness: narcoleptic patients, idiopathic hypersomniac patients, hypersomniac patients with sleep apnea syndrome. We analyzed polygraphic diurnal recordings of 45 min duration obtained under standardized conditions. We called the percentage of total sleep time during the 45-min recording the polygraphic index of sleepiness. The polygraphic score of sleepiness is determined by the latencies and total durations of the individual sleep stages. Because deeper sleep stages correspond to more pronounced sleepiness than do superficial sleep stages, we introduced coefficients for each sleep stage. We present a formula for calculating a score in a single figure that gives a good indication of the patient's sleepiness and makes inter- and intraindividual comparison possible. Separate REM and NREM sleep scores are also given. Key Words: Sleep polygraphy-Sleepiness index-Sleepiness scoreNarcolepsy-Hypersomnia.
The quantitative evaluation of pathological diurnal sleepiness has only recently received attention. In 1982, Dement and Carskadon (1) noted that research was needed in this area and organized a symposium devoted to this question. The findings presented at that symposium (2) were based, for the most part, on the multiple sleep latency test (MSLT) and a modified version of this test, the Repeated Test of Sustained Wakefulness (3). Although these articles presented new, useful information, they used almost exclusively the latency of the first sleep stage in the recording for the quantitative evaluation of sleepiness. We have tried another approach. Using 45-min polygraphic recordings, we evaluated the latencies and the total durations of all sleep stages, i.e., nearly all the information on wakefulness and sleep in the recording. This test has the advantage of being relatively short while giving much quantified information on the patients' diurnal sleepiness. MATERIALS AND METHODS
We examined polygraphically 10 patients with idiopathic narcolepsy-cataplexy, 10 patients suffering from idiopathic hypersomnia, 10 patients with hypersomnia-sleep apnea Accepted for publication September 1985. Address correspondence and reprint requests to Dr. B. Roth at Department of Neurology, Katerinska 30, 120 00 Prague 2, Czechoslovakia.
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syndrome, and 10 healthy controls. The recordings lasted 45 min and were performed between 2:00 and 4:00 p.m. The patients had not taken any sleep-related medication for 1 week prior to the test. The empirical experiments conform to the Declaration of Helsinki. The recordings were divided into epochs of 30 s each and scored according to Rechtschaffen and Kales (4). The latencies and total durations of all sleep stages were assessed. The latencies, given in min, were measured from the beginning of the test until the first epoch scored as a specific sleep stage. They were labeled as L t , Lz, L 3 , L4 , and LREM • If one of the sleep stages did not occur in the recording, it was assigned a latency of 45 min. Total durations of the individual sleep stages were given as a percentage of the total sleep time and were labeled T 1- TREM' To serve the same purpose as a-wave index and o-wave index used in electroencephalography, we propose introducing the Polygraphic Sleepiness Index (PSI), which indicates total sleep duration as a percentage of the total duration of the test. We also propose introducing Polygraphic Score of Sleepiness (PSS), expressed in points that are given on the basis of a quantitative evaluation of the latencies and the total durations of all sleep stages in the recording. Because the shorter the sleep latency the more intense the sleepiness, we deduct from the total duration of the test (45 min) the individual sleep stage latency. We must also take into consideration that deeper sleep stages show more intense sleepiness than do superficial sleep stages. It is necessary therefore, to introduce coefficients for all sleep stages, which we label k\-kREM • After many trials we have come to the conclusion that the most appropriate coefficients are: 1, 2, 5, 10, and 10, respectively. The points for the latencies are therefore (45 - L t ) x 1 + (45 - L 2) x 2 + (45 - L~) x 5 + (45 - L4 ) x 10 + (45 LREM) x 10. To assign points for the total durations of the individual sleep stages, we must take two facts into consideration. First, it is evident that the longer the duration of sleep activity, the deeper the sleepiness. Second, the sleep stage itself must be considered, i.e., a 10% duration of sleep stage 4 indicates more intense sleepiness than does the same duration of sleep stages 1 or 2. This example shows that to assign points for the total durations of the individual sleep stages, it is also necessary to use the above coefficients. The number of points given for the total durations of the individual sleep stages therefore, is: T\ x 1 + T2 X 2 + T3 X 5 + T4 X 10 + TREM X 10. The total score for the PSS is the sum of the points given for the latencies and for the total durations of all sleep stages in the recording. It is also possible to assess REM and NREM sleep scores separately. For the statistical evaluation of our material, Fisher's test and the Mann Whitney U test were used.
RESULTS The occurrences, latencies, and total durations of all sleep stages in our patients and controls are published elsewhere (5). Table 1 summarizes the PSIs and PSSs of our patients and controls. The PSIs give an idea of the intensity of sleepiness; however, it is not very reliable because even healthy people sometimes have a PSI equal to 80 or 90%, mainly because of the presence of stage 1 sleep. The PSSs are far more reliable. Table 1 presents our patients' total PSSs as well as their separate REM and NREM sleep scores. Both total scores and NREM sleep scores are significantly different between the control group and all three groups of patients. Only narcoleptic patients have a high REM sleep score; the difference between REM sleep scores Sleep. Vol. 9. No. I. 1986
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SLEEPINESS INDEX AND SCORE TABLE 1. Polygraphic index of sleepiness and polygraphic score of sleepiness (PSSs - NREM, REM, and total) PSI
Diagnosis Control group (N
=
10)
Iodiopathic narcolepsy (N Idiopathic hYpersomnia (N Hypersomnia-sleep apnea (N = 10)
= =
10) 10)
Average 31.8 35.3 SD 0--97.5 Range 89.0" 14.0 57.8-100.0 78.0" 16.1 46,2-100,0 84.815.3 45.5-98.2
PSS (NREM) 56.7 66.7 0-207.5 366.0· 246.0 65.0-800,0 254.2130.6 61.0--495.0 258.9137.9 110.0--578.5
PSS (REM)
PSS (Total)
0 0 0 476.0· 192.2 0-750.0 0 0 0 52.5 157.5 0--525.0
56.7 66.7 0-207.5 842.0" 241.2 485.0-1,305.0 254,2130.6 61. 0--495,0 311.4191.6 110.0--716,0
PSI, polygraphic sleepiness index; PSS, polygraphic score of sleepiness; .p < 0.0 I, statistically significant.
in narcoleptic patients and the other three groups is highly significant. Table I also shows that the total PSSs are significantly higher in patients with narcolepsy than in the other two groups of patients because the NREM and REM sleep scores are combined. The high NREM sleep score in narcoleptic patients shows convincingly that this syndrome is characterized by the facilitation not only of REM sleep but also of NREM sleep,
DISCUSSION Our method of evaluating polygraphic recordings yields important quantified dat?, ~x pressed in one number, on the degree of a patient's sleepiness. If the polygraphic recording, the evaluation of the recording, and the analysis of the results are conducted in a standardized fashion, as described above, it is possible to compare the findings obtained over time not only in the same patient but also across patients. Separate REM sleep and NREM sleep scores make a simple, quick assessment of the disorder's intensity in REM sleep as well as NREM sleep possible. These quantified findings are useful in the assessment of working ability, fitness to drive, etc. They are also helpful in evaluating the effect of a treatment. The validity of the test, particularly its reproducibility, must still be verified.
REFERENCES I. Dement WC, Carskadon MA, Current perspectives on daytime sleepiness: The issues. Sleep 1982;5(suppl 2):S56--66. 2, Carskadon MA (ed), Current perspectives on daytime sleepiness. Sleep 1982;5(supp1 2):S55-202, 3. Hartse KM, Roth T, Zorick FJ. Daytime sleepiness and daytime wakefulness: the effect of instruction. Sleep 1982;5(suppl 2):SI07-18. 4. Rechtschaffen A, Kales A (eds). A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects. Public Health Service, U.S. Government Printing Office, Washington, D.C,,1968. 5. Roth B, Nevsima10va S, Sonka K, Docekal p, A quantitative polygraphic study of daytime somnolence and sleep in patients with excessive diurnal sleepiness, Arch Suisse Neurol Neurochir Psychiatry 1984;135:26572.
Sleep, Vol. 9, No.1, 1986
