SLEEP

Helmus, Todd; Rosenthal, Leon; Bishop, Christopher; Roehrs, Timothy; Syron, Mary Lou; Roth, Thomas

doi: 10.1093/sleep/20.4.251pmid: 9231950

Summary:Eleven narcoleptic patients and 22 age- and gender-matched normal controls participated in a study to determine the alerting effects of differing nap lengths. All narcoleptic patients had been previously diagnosed [mean sleep latency on the multiple sleep latency test (MSLT) ≤ 5 minutes with two or more sleep-onset rapid eye movement periods (SOREMPs)]. Healthy, normal subjects with a mean sleep latency on the screening MSLT ≥ 8 minutes were randomly assigned to one of two groups (i.e. sleep-deprived and alert). All subjects completed two experimental night and days with at least 5 days between sessions. On the evening prior to each experimental day, narcoleptic and alert subjects spent 8 hours in bed and sleep-deprived subjects spent 0 hours in bed. The following day, all subjects underwent one of two napping conditions, 15 or 120 minutes in bed. Both naps were terminated at noon. Every subject underwent both conditions and the order of conditions was counterbalanced. From 1215 to 1355 hours all subjects underwent a modified MSLT. At 1500 hours, the subjects had a 1-hour nap. The results showed that the 120-minute nap condition was more beneficial than the 15-minute nap. Narcoleptic and sleep-deprived subjects were shown to have comparable levels of sleepiness on the modified MSLT. However, a differential response pattern on their latency to sleep was noted on the 1-hour nap. Sleep-deprived subjects were shown to be differentially more alert following a 120-minute nap opportunity. In contrast, for narcoleptic patients the beneficial effects of the nap were lost when tested 3 hours later. These results show that narcoleptic patients benefit from a longer nap but that these benefits are short-lived.

Alloway, Christi E. D.; Ogilvie, Robert D.; Shapiro, Colin M.

doi: 10.1093/sleep/20.4.258pmid: 9231951

Summary:Daytime sleep tendency was assessed in 10 drug-free patients with narcolepsy-cataplexy and 10 normals matched for age and gender. Following nocturnal polysomnography, the alpha attenuation test (AAT) and the multiple sleep latency test (MSLT) were administered during five sessions occurring at 2-hour intervals beginning at 0900 and 1000 hours, respectively. For the AAT, participants were polysomnographically recorded for 8 minutes while seated in an illuminated room with their eyes alternately opened and closed. Power spectral analyses of electroencephalograph (EEG) activity at 02–A1 (10 second epochs) were calculated using fast Fourier transformations (FFT) within the alpha frequency range (8–12 Hz) to obtain ratios of mean eyes-closed to mean eyes-open alpha power (i.e. the alpha attenuation coefficient, AAC). The narcoleptics were sleepier than the normals as indicated by a significantly smaller mean AAC and a significantly shorter mean latency to stage 1 on the MSLT. These findings suggest that the AAT may provide a quick and practical objective assessment of the excessive daytime sleepiness (EDS) associated with narcolepsy.

Dinges, David F.; Pack, Frances; Williams, Katherine; Gillen, Kelly A.; Powell, John W.; Ott, Geoffrey E.; Aptowicz, Caitlin; Pack, Allan I.

doi: 10.1093/sleep/20.4.267pmid: N/A

Summary:To determine whether a cumulative sleep debt (in a range commonly experienced) would result in cumulative changes in measures of waking neurobehavioral alertness, 16 healthy young adults had their sleep restricted 33% below habitual sleep duration, to an average 4.98 hours per night [standard deviation (SD) = 0.57] for seven consecutive nights. Subjects slept in the laboratory, and sleep and waking were monitored by staff and actigraphy. Three times each day (1000, 1600, and 2200 hours) subjects were assessed for subjective sleepiness (SSS) and mood (POMS) and were evaluated on a brief performance battery that included psychomotor vigilance (PVT), probed memory (PRM), and serial-addition testing. Once each day they completed a series of visual analog scales (VAS) and reported sleepiness and somatic and cognitive/emotional problems. Sleep restriction resulted in statistically robust cumulative effects on waking functions. SSS ratings, subscale scores for fatigue, confusion, tension, and total mood disturbance from the POMS and VAS ratings of mental exhaustion and stress were elevated across days of restricted sleep (p = 0.009 to p = 0.0001). PVT performance parameters, including the frequency and duration of lapses, were also significantly increased by restriction (p = 0.018 to p = 0.0001). Significant time-of-day effects were evident in SSS and PVT data, but time-of-day did not interact with the effects of sleep restriction across days. The temporal profiles of cumulative changes in neurobehavioral measures of alertness as a function of sleep restriction were generally consistent. Subjective changes tended to precede performance changes by 1 day, but overall changes in both classes of measure were greatest during the first 2 days (P1, P2) and last 2 days (P6, P7) of sleep restriction. Data from subsets of subjects also showed: 1) that significant decreases in the MSLT occurred during sleep restriction, 2) that the elevated sleepiness and performance deficits continued beyond day 7 of restriction, and 3) that recovery from these deficits appeared to require two full nights of sleep. The cumulative increase in performance lapses across days of sleep restriction correlated closely with MSLT results (r = −0.95) from an earlier comparable experiment by Carskadon and Dement (1). These findings suggest that cumulative nocturnal sleep debt had a dynamic and escalating analog in cumulative daytime sleepiness and that asymptotic or steady-state sleepiness was not achieved in response to sleep restriction.

Weaver, Terri E.; Kribbs, Nancy Barone; Pack, Allan I.; Kline, Lewis R.; Chugh, Deepak K.; Maislin, Greg; Smith, Philip L.; Schwartz, Alan R.; Schubert, Norman M.; Gillen, Kelly A.; Dinges, David F.

doi: 10.1093/sleep/20.4.278pmid:

Chervin, Ronald D.; Theut, Sarah; Bassetti, Claudio; Aldrich, Michael S.

doi: 10.1093/sleep/20.4.284pmid: 9231954

Summary:Effectiveness of continuous positive airway pressure (CPAP) as a treatment for obstructive sleep apnea can be limited by poor compliance, but little is known about how to improve compliance. We performed a randomized, controlled clinical trial among 33 subjects of two interventions to improve compliance. One group of subjects received weekly phone calls to uncover any problems and encourage use, another received written information about sleep apnea and the importance of regular CPAP use, and a third served as control subjects. We found that intervention improved CPAP compliance (p = 0.059) and that the effect was particularly strong when intervention occurred during the first month of CPAP treatment (p = 0.004). Although the sample size did not allow definitive investigation of other explanatory variables, subjects with lower levels of education or those with relatives who used CPAP may have benefited from intervention more than other subjects. We conclude that simple, inexpensive efforts to improve compliance with CPAP can be effective, especially when applied at the start of CPAP treatment, but optimal intervention may vary with certain patient characteristics.

Lavigne, Gilles J.; Lobbezoo, Frank; Rompré, Pierre H.; Nielsen, Tore A.; Montplaisir, Jacques

doi: 10.1093/sleep/20.4.290pmid: N/A

Summary:Cigarette smoking has been associated with sleep disturbances. However, little is known about how smoking affects restless legs syndrome (RLS) and sleep bruxism, two movement disorders associated with sleep. From a nationwide survey of 2,019 Canadian adults, we estimated the prevalence of smoking to be 36%. Although there was no difference between smokers and nonsmokers for RLS prevalence, almost twice as many smokers (12%) as nonsmokers (7%) were aware of experiencing sleep bruxism. The estimated risk of a smoker suffering from RLS was nonsignificant. On the other hand, the risk of a smoker grinding his or her teeth was moderate (odds ratio = 1.9). Analysis of sleep laboratory findings revealed no differences in motor RLS and periodic leg movements in sleep (PLMS) indices between smoking and nonsmoking patients; after adjustment for age, there were no differences in sleep efficiency, latency, number of awakenings, or the arousal index for the RLS/PLMS patients. Among those suffering from bruxism, smokers had more tooth-grinding episodes than did nonsmokers (35.0 vs. 7.0; p = 0.056); none of the sleep variables differentiated sleep bruxism smokers from nonsmokers. It appears that cigarette smoking does not influence RLS/PLMS, whereas the risk that smoking and tooth grinding are concomitant is moderate. Smoking was not significantly associated with more motor activity in RLS/PLMS, but more grinding was noted in sleep bruxism.

Haimov, Iris; Lavie, Peretz

doi: 10.1093/sleep/20.4.294pmid: 9231956

Summary:Changes in sleep—wake patterns are among the hallmarks of biological aging. Elderly persons complain of daytime drowsiness and difficulties in initiating and maintaining sleep. The question of whether age-related changes in sleep—wake distribution are the result of a dimunition in amplitude of the endogenous circadian pacemaker, resulting in a decline in nocturnal sleep tendency and an increase in diurnal sleep tendency, or a manifestation of the impact of the medical and psychosocial burden on sleep has not yet been fully determined. In the present study, we utilized a 7/13 ultrashort sleep-wake paradigm to investigate the 24-hour sleep propensity function (SPF) in healthy elderly persons. Seventeen healthy, elderly males, aged 65-78 years, and eight young males, aged 19-26, participated in the study. All elderly subjects were living independently in the community and were vigorous, physically active, and socially engaged. The young adult subjects were students living on campus, all with the same daily schedule. As anticipated, Polysomnographic measures from the night prior to experimental periods differed between the elderly and young subjects. Specifically, the elderly had a reduction in percentage of sleep stage 3/4 and in sleep efficiency. The results of the 7/13 ultrashort sleep-wake paradigm showed that although aging did not affect the overall structure of the SPF, there was an age-related trend toward lower circadian amplitude and advanced phase. Our findings suggest that these age-related changes in sleep propensity may contribute to the difficulties in initiating sleep and to the early morning awakening.

Casagrande, Maria; De Gennaro, Luigi; Violani, Cristiano; Braibanti, Paride; Bertini, Mario

doi: 10.1093/sleep/20.4.301pmid: 9231957

Summary:The aim of this study was to assess whether a finger-tapping task (FIT), in which normal subjects repeatedly tap on a button while falling asleep, could be less disturbing and provide comparable information on the sleep onset period (SOP) with respect to a reaction-time task (RTT) to acoustic stimuli, in which the onset of sleep can be delayed by the arousing effect of the acoustic stimuli.Twelve subjects slept at their homes and six slept in a sleep laboratory for four consecutive nights. After one adaptation night and one baseline night, subjects were required to fall asleep in the third and fourth nights, biman-ually performing either a RTT or a FIT.The results indicate that the FTT interferes less with the SOP compared to the RTT and suggest that the FIT provides further advantages as a behavioral measure of the transition from wakefulness to sleep. In fact, the tapping task is associated with significantly shorter behavioral and Polysomnographic sleep onset latencies and with a greater proportion of slow-wave sleep (SWS) during the transition from wakefulness to sleep compared with the RTT. Furthermore, correlations among subjective, behavioral, and electroencephalograph (EEG) latencies confirm the validity of the finger-tapping task as a behavioral measure of sleep onset.

Preud'homme, X. A.; Lanquart, J.-P.; Mendlewicz, J.; Linkowski, P.

doi: 10.1093/sleep/20.4.313pmid: 9231958

Summary:The distribution of delta activity across successive nonrapid eye movement (NREM) sleep episodes and its night-to-night stability across three consecutive nights were investigated by studying delta power with spectral analysis in 31 healthy young men. Repeated-measures analysis of variance (ANOVA) with polynomial contrast was applied to grouped data of absolute delta power and of three indexes: 1) the rate of delta power per NREM episode to its duration, 2) the standardized rate for the last NREM episode, and 3) the logarithm of the standardized rate. A significant linear decrease across NREM episodes was observed for each variable in each successive night. In addition, using night as a second within-subjects factor, no night effect was observed. Yet, the subsequent analysis of the logarithmic data yielded greater F values in all three nights’ data as well as a linear function that accounted for a greater proportion of total variance than the analysis of the nonlogarithmic data. Since a linear decline for the logarithm of a variable implies an exponential distribution for that variable, we conclude that delta activity is distributed exponentially across NREM episodes, and this finding shows a remarkable night-to-night stability.