Sleepiness is not the inverse of alertness: evidence from four sleep disorder patient groups

The constructs “sleepiness” and “alertness” are often assumed to be reciprocal states of consciousness. This distinction is of increasing concern in relation to psychomotor performance tasks such as driving. We developed two separate subjective scales of alertness to complement existing sleepiness scales. Subjective sleepiness and alertness were compared in four groups of sleep-disordered patients. In a 175-patient cohort [25 narcoleptics and 50 each with sleep apnea, insomnia and periodic leg movement disorder (PLMD)], the Epworth Sleepiness Scale (ESS) was used to measure sleepiness while the Toronto Hospital Alertness Test (THAT) and ZOGIM Alertness Scale (ZOGIM-A) were used to measure alertness. Significant differences existed for sleepiness scores, with narcoleptics scoring highest on the ESS, followed by sleep apnea, with similar ESS scores for insomnia and PLMD. By contrast, alertness scores on both the THAT and ZOGIM-A did not differ significantly between the four groups. Sleepiness scores show a correlation of close to nil to alertness scores for the combined sleep disorder patient cohort, with the exception of insomnia patients, where a modest but significant inverse relationship was noted between sleepiness and alertness. Subjective states of impaired alertness and excessive sleepiness are independent constructs in the evaluation of sleep-disordered patients. The specific primary sleep disorder diagnosis may play a relevant role in mitigating this interrelationship.     

Subjective and objective sleepiness in monozygotic twins discordant for chronic fatigue syndrome

STUDY OBJECTIVE: To examine the association of chronic fatigue syndrome (CFS) with measures of objective and subjective sleepiness. DESIGN: Monozygotic co-twin control study. SETTING: Academic medical center. PATIENTS AND PARTICIPANTS: Twenty monozygotic twin pairs discordant for CFS. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: All twins completed an Epworth Sleepiness Scale (ESS), 4 Stanford Sleepiness Scales (SSS), and underwent a standard 4-nap multiple sleep latency test. We compared the ESS scores, average SSS scores, and average sleep latency in CFS and healthy twins. The CFS twins reported more sleepiness as measured by mean scores on the ESS (10.9 vs 8.2; 95% confidence interval [CI] = 0.3-5.5; P = .03) and the SSS (3.4 versus 2.1; 95% CI = 0.7-1.9; P < .001). The mean sleep latency on the Multiple Sleep Latency Test was not significantly different between the CFS and healthy twins (8.9 vs 10.0 minutes; 95% CI -4.4-1.7; P = .33). Mean SSS scores increased among the CFS twins and decreased among healthy twins from nap 1 to nap 4 (P < .001). The individual ESS scores and mean sleep latencies on the Multiple Sleep Latency Test were negatively correlated for all the twins (Pearson's r = - 0.40; P = .01), with a slightly stronger association among the healthy twins (Pearson's r = -0.42, P = .07) than the CFS twins (Pearson's r = -0.36, P = .15). CONCLUSIONS: CFS twins reported significantly more subjective sleepiness than their healthy co-twins despite similar nonpathologic mean sleep latencies on the Multiple Sleep Latency Test. Patients with CFS may mistake their chronic disabling fatigue for sleepiness.     

Daytime sleepiness and alertness in patients with Parkinson disease

STUDY OBJECTIVES: The goal of the study was to objectively measure daytime sleepiness and alertness in patients undergoing treatment for idiopathic Parkinson disease (PD) and assess potential contributing factors. DESIGN: Prospective study. SETTING: An accredited sleep disorders center in a university-based medical center in a large urban area. PATIENTS: Twenty consecutive subjects with idiopathic PD were recruited from a tertiary-care movement disorders clinic. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Patients underwent polysomnography, with a Multiple Sleep Latency Test (MSLT) and a Maintenance of Wakefulness Test (MWT) on the following day. Forty-seven percent of the sample was pathologically sleepy according to the MSLT, but only 26% had abnormal MWT scores. There was also a different pattern of correlations between predictors of sleepiness and MSLT and MWT scores. Percentage of stage 1 sleep had the largest correlation with MSLT (-0.42), while pergolide equivalents had the largest correlation with MWT (-0.70). CONCLUSIONS: In this sample of subjects with PD, severe daytime sleepiness was common and was related to poor sleep quality. Daytime alertness as measured by the MWT was impaired as medication burden increased.     

The clinical value of the maintenance of wakefulness test (MWT) in the differentiation of children with attention deficit hyperactivity disorder (ADHD) and disorders of excessive somnolence

Summary Introduction   Attention deficit hyperactivity disorder is one of the most common child and adolescent psychiatric disorders. Probably a dysfunctional arousal regulation may play an important role in its pathogenesis. According to this hypothesis ADHD children may present an hypoarousal state with impaired daytime vigilance when confrontated with monotonous, repetetive tasks. Methods   We assessed the daytime wakefulness of 23 ADHD children and 6 children with excessive somnolence (narcolepsy, idiopathic CNS hypersomnia) using the Maintenance of Wakefulness Test (MWT) as a measure to determine objectively a subjects' ability to stay awake under soporific conditions. Results   Results indicate that there is no impaired daytime wakefulness in ADHD children, whether their nighttime sleep was disturbed or not. Mean sleep latencies across all MWT trials were similar for both groups groups (17.2 min. vs 16.3 min). In contrast children with an increased daytime sleepiness presented a shortened mean sleep latency during the trials (8.9 min). Aditionally more children of this group fell asleep during MWT compared to ADHD children (72 % vs 40.6 %). Conclusion   We speculate that due to the occurrence of attention problems in both disorders, the MWT might become a feasable, objective instrument in clinical practice for differential diagnostic.     

Maintenance of wakefulness test as a predictor of driving performance in patients with untreated obstructive sleep apnea

STUDY OBJECTIVE: To determine the ability of Maintenance of Wakefulness Test (MWT) to predict simulated driving performance in patients suffering from sleep apnea syndrome. DESIGN: Study involving one hour of simulated driving, one night of polysomnography (PSG), and a 4 x 40-minute MWT. SETTING: Sleep laboratory. PATIENTS: Thirty male patients with untreated obstructive sleep apnea syndrome (OSAS) (mean age [+/- SD] = 51 +/- 8 years, range 34-62; mean body mass index (BMI) [+/- SD] = 29 +/- 3, range 24-37; mean apnea/hypopnea index (AHI) [+/- SD] = 43 +/- 24, range 14-96). As defined by MWT mean sleep latency, 23.3% of the patients were sleepy (0-19 min), 33.3% were alert (20-33 min), and 43.4% were fully alert (34-40 min). MEASUREMENTS: Nocturnal PSG, mean sleep latency at 4 x 40-minute MWT trials, Epworth Sleepiness Scale (ESS), and standard deviation from the center of the road (SDS) on driving simulator. RESULTS: Mean MWT scores inversely correlated with SDS during the simulated driving session (Pearson's r = -0.513, P < 0.01). We found a significant effect of MWT groups (sleepy, alert, or fully alert) on SDS (ANOVA, F(2, 29) = 5.861, P < 0.01). Post hoc tests revealed that the sleepy group had a higher SDS than the fully alert group (P = 0.006). ESS, AHI, microarousal index, and total sleep time did not predict simulated driving performance. CONCLUSIONS: A pathological MWT mean sleep latency (0-19 min) is associated with simulated driving impairment. Before MWT can be used to predict the driving ability of untreated patients with OSAS, further studies are needed to confirm that pathological MWT scores are associated with real driving impairment.     

Arousal components which differentiate the MWT from the MSLT

STUDY OBJECTIVES: The purpose of this study was to determine the relative contribution of the instruction to maintain wakefulness versus posture change as major components determining sleep latency in the MWT as compared to the MSLT. DESIGN AND SETTING: After adaptation, subjects spent 3 nights and the following days in the laboratory. On each day, Ss had eight sleep latency measurements including four sleep latency tests from two of the following conditions: Lay down and Sleep (MSLT); Lay down and stay Awake; Sit up and Sleep; Sit up and stay Awake (MWT); and sit in a chair in front of a Computer and stay awake. PARTICIPANTS: Participants were 14 young adult normal sleepers. INTERVENTIONS: NA. MEASUREMENT AND RESULTS: Significant differences in sleep latency were found for each condition with respect to all of the others except that the Computer condition did not differ from the Sit-Awake condition. Means for conditions were: Lay-Sleep -11.1 minutes; Sit-Sleep -17.7 minutes; Lay-Awake - 21.7 minutes; Sit-Awake - 29.0 minutes; Computer - 30.1 minutes. Correlations between conditions declined as subjects sat up. CONCLUSIONS: The MWT differs from the MSLT by taking advantage of the arousal system (motivation and posture) to maintain alertness (i.e., increase sleep latency). These arousal effects are additive. MSLT results may not always correlate well with MWT results because the MWT measures the combined effects of the sleep and arousal systems while the MSLT, in ideal situations, measures only sleepiness.     

Physiological sleep tendency and ability to maintain alertness at night

The maintenance of wakefulness test (MWT) and repeated test of sustained wakefulness (RTSW) were compared to the multiple sleep latency test (MSLT) during nighttime hours to evaluate differential sensitivity to variation in physiologic sleepiness/alertness. The degree of sleepiness varied by time of night and was further manipulated by varying prior sleep. Seven healthy normal sleepers were evaluated on the MWT, RTSW, MSLT, a digit symbol substitution test and the Wilkinson addition test in a protocol beginning at 2200 h and terminating at 0830 the following morning. A counterbalanced, crossover design compared an evening nap condition to a no-nap condition. The MWT and RTSW discriminated between nap and no-nap conditions, but the MSLT did not. This suggests that in some situations the MWT and RTSW may be more sensitive to changes in physiologic sleepiness/alertness than the MSLT. The data are discussed in terms of possible methodologic limits of the MSLT and the relationship between physiologic sleep tendency and the capacity to maintain alertness.     

Predictors of objective sleep tendency in the general population

STUDY OBJECTIVES: Daytime sleepiness is a pervasive problem that is associated with a significant public-health burden. Although self-reported measures of daytime sleepiness may be useful in identifying at-risk individuals, there is significant controversy because there are no population-based data relating subjective and objective measures of daytime sleep tendency. The aims of this study were to examine the associations between the Multiple Sleep Latency Test (MSLT), an objective measure of daytime sleep tendency, and self-reported information on the Epworth Sleepiness Scale (ESS) and nighttime sleep duration in the general population. DESIGN: Cross-sectional study. SETTING AND PARTICIPANTS: Population-based sample of 261 women and 371 men, mean age of 50.8 years, enrolled in the Wisconsin Sleep Cohort Study. MEASUREMENTS: MSLT, ESS, and self-reported sleep duration prior to the MSLT. RESULTS: Using survival analysis to model the time to sleep onset during the MSLT, we found that individuals with an intermediate (6-11) and high (> or = 12) ESS score had a 30% and 69% increase in risk for sleep onset during the MSLT, respectively, compared to individuals with a low ESS score (< or = 5). A dose-response relationship between self-reported duration of nighttime sleep and objective sleep tendency was also observed. Compared to individuals reporting more than 7.50 hours of sleep (highest tertile), individuals reporting 6.75 to 7.50 hours and less than 6.75 hours (lowest tertile) had a 27% and 73% increase in risk for sleep onset during the MSLT, respectively. CONCLUSIONS: Subjective reports of daytime sleep tendency on the ESS and the duration of nighttime sleep are associated with the results of the MSLT in the general population.     

Factors associated with maintenance of wakefulness test mean sleep latency in patients with mild to moderate obstructive sleep apnoea and normal subjects

This study investigated the possible factors related to the Maintenance of Wakefulness Test (MWT) mean sleep latency. A second analysis explored the characteristics of subjects who had discrepant Epworth Sleepiness Scale (ESS) and MWT scores. A total of 151 subjects (110 mild to moderate obstructive sleep apnoea (OSA) patients and 41 control subjects) were recruited for the study. The subjects completed an overnight Polysomnography (PSG), MWT, cognitive, performance and vigilance tasks and answered self-report questionnaires on mood and sleepiness. A forward stepwise multiple regression was performed on MWT mean sleep latency. The predictor variables age (r = 0.28), subjective sleep history for 1 week prior to MWT (sleep diary; r = 0.19) and number of >4% SaO2 Dips during the PSG (r = -0.21) best explained the MWT results, but only accounted for 12.8% of the variance in the test. It was found that 33% of subjects had discrepant ESS and MWT scores. A new variable was created to analyse these subjects (MWT/ESS discrepancy score; MED). A forward stepwise multiple regression analysis found that depression, performance errors and sleep disordered breathing explained 13.4% of the variance in MED scores. The MWT is a complex behavioural test whose scores do not seem to have a very robust relationship with potential predictors and co-correlates. Further comprehensive study is needed if the test is to be used in a diagnostically meaningful way.     

Manipulation of core body and skin temperature improves vigilance and maintenance of wakefulness in narcolepsy

CONTEXT: Impaired vigilance and sleepiness are two majordaily complaints of patients with narcolepsy. We previously showed their sleepiness to be correlated to an abnormally regulated skin temperature, i.e., increased distal skin temperature compared with proximal skin temperature. OBJECTIVE: Our goal was to investigate a possible causal contribution of skin temperature disturbances to impairments in the ability to maintain vigilance and wakefulness in narcolepsy. DESIGN: In a modified constant routine protocol, the Psychomotor Vigilance Task (PVT) and the Maintenance of Wakefulness Test (MWT) were repeatedly assessed. Meanwhile, skin and core body temperatures were mildly manipulated within the thermoneutral range of the normal diurnal rhythm using a thermosuit and hot or cold food and drinks. SETTING: Tertiary narcolepsy referral center in a university hospital PATIENTS OR OTHER PARTICIPANTS: Eight patients (5 males) diagnosed with narcolepsy with cataplexy according to the ICSD-2 criteria (mean age +/- SD: 28.6 +/- 6.4, range 18-35 years). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): MWT sleep latency and PVT response speed. RESULTS: Compared to core cooling, core warming attenuated the typical decline in PVT response speed with increasing time-on-task by 25% (P = 0.02). Compared to distal skin warming, distal skin cooling increased the time that the patients were able to maintain wakefulness by 24% (distal warming: 1.88 min. vs. distal warming: 2.34 min.; P < 0.01). CONCLUSIONS: Core body and skin temperatures causally affect vigilance and sleepiness in narcolepsy. This could lead to future practical applications.     

Socializing by Day May Affect Performance by Night: Vulnerability to Sleep Deprivation is Differentially Mediated by Social Exposure in Extraverts vs Introverts

Study Objectives:

To examine the effects of socially enriched versus socially impoverished environments on performance and alertness decline during sleep deprivation in extraverts versus introverts.

Design:

Participants (n = 29 men, n = 19 women) were assigned to socially enriched (n = 24; 13 introverts, 11 extraverts) or socially impoverished (n = 24; 12 introverts, 12 extraverts) conditions (activities matched) for 12 hours (1000–2200) on Day 1 followed by 22 hours of sleep deprivation (2200-2000; 36 h awake total), monitored by actigraphy. The median split of volunteers'' Eysenck Extraversion scores was used for extravert/introvert categorization. The Psychomotor Vigilance Task (PVT), modified Maintenance of Wakefulness Test (MWT), and Stanford Sleepiness Scale (SSS) were administered every 2 hours throughout. PVT speed, transformed lapses, modified MWT sleep-onset latency, and SSS were analyzed using mixed-model analyses of variance, with covariates of age and total actigraphic activity during enrichment or impoverishment.

Setting:

Residential sleep/performance testing facility.

Participants:

Forty-eight healthy adults (aged 18–39).

Interventions:

Twelve hours of socially enriched or isolated environments in extraverts and introverts prior to sleep deprivation.

Results

Social experience interacted with personality type to affect alertness and vigilance. Social enrichment, as compared with social impoverishment, was associated with more PVT lapses at 04:00 overall. Similarly, following social enrichment, PVT speed was significantly slower among extraverts than among introverts during sleep deprivation, but no personality-group differences emerged following social impoverishment. MWT sleep latency and SSS subjective sleepiness did not show significant personality or social-condition effects during sleep deprivation.

Conclusions:

The effect of social exposure on vulnerability or resiliency to sleep deprivation was modulated by introversion and extraversion. Extraverts exposed to social environments were more vulnerable to subsequent sleep deprivation than were introverts.

Citation:

Rupp TL; Killgore WDS; Balkin TJ. Socializing by day may affect performance by night: vulnerability to sleep deprivation is differentially mediated by social exposure in extraverts vs introverts. SLEEP 2010;33(11):1475-1485.     

Daytime Sleepiness and Driving Performance in Patients with Obstructive Sleep Apnea: Comparison of the MSLT,the MWT,and a Simulated Driving Task

Study Objectives:

To test the reliability of a driving-simulation test for the objective measurement of daytime alertness compared with the Multiple Sleep Latency Test (MSLT) and with the Maintenance of Wakefulness Test (MWT), and to test the ability to drive safely, in comparison with on-road history, in the clinical setting of untreated severe obstructive sleep apnea.

Design:

N/A.

Setting:

Sleep laboratory.

Patients or Participants:

Twenty-four patients with severe obstructive sleep apnea and reported daytime sleepiness varying in severity (as measured by the Epworth Sleepiness Scale).

Interventions:

N/A.

Measurements and Results:

Patients underwent MSLT and MWT coupled with 4 sessions of driving-simulation test on 2 different days randomly distributed 1 week apart. Simulated-driving performance (in terms of lane-position variability and crash occurrence) was correlated with sleep latency on the MSLT and more significantly on the MWT, showing a predictive validity toward the detection of sleepy versus alert patients with obstructive sleep apnea. In addition, patients reporting excessive daytime sleepiness or a history of car crashes showed poorer performances on the driving simulator.

Conclusions:

A simulated driving test is a suitable tool for objective measurement of daytime alertness in patients with obstructive sleep apnea. Further studies are needed to clarify the association between simulated-driving performance and on-road crash risk of patients with sleep disordered breathing.

Citation:

Pizza F; Contardi S; Mondini S; Trentin L; Cirignotta F. Daytime sleepiness and driving performance in patients with obstructive sleep apnea: comparison of the MSLT, the MWT, and a simulated driving task. SLEEP 2009;32(3):382-391.     

The maintenance of wakefulness test in normal healthy subjects

STUDY OBJECTIVES: The Maintenance of Wakefulness Test (MWT) examines an individual's ability to stay awake in an environment of decreased sensory stimulation. Only 1 previous study has systematically examined the MWT in normal healthy subjects. SETTING: Sleep disorders unit laboratory PARTICIPANTS AND DESIGN: 31 subjects (mean age 48.5 years, SD 9.6; 8 women) were randomly selected via the telephone directory within a 30-km radius of the test centers. They answered a general screen for health complaints (respiratory, cardiovascular, and psychiatric disorders) and sleep difficulties (snoring). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Overnight polysomnography and a 40-minute MWT the following day were performed on all subjects. Mean sleep latency to the first epoch of unequivocal sleep during the 40-minute trial MWT was 36.9 +/- 5.4 (SD) minutes. The lower normal limit, defined as 2 SD below the mean, was therefore 26.1 minutes. Mean sleep latency for the first 20 minutes of the trial (with sleep latency defined as time to the first appearance of 1 epoch of stage 1 sleep or a 10-second microsleep) was 18.6 +/- 2.3 minutes, with a lower normal limit of 14.0 minutes. CONCLUSIONS: The mean results are consistent with previously published normative data. However, the SDs found in this study are smaller, and, thus, the lower normal limit suggested here is 4 to 6 minutes longer. The subjects in this study were randomly selected from the general population and may, therefore, be a truer representation of the normal population than in the previous study in which subjects were recruited via hospital advertisements and word of mouth.     

Zaleplon and zolpidem objectively alleviate sleep disturbances in mountaineers at a 3,613 meter altitude

STUDY OBJECTIVES: To assess the effects of zolpidem and zaleplon on nocturnal sleep and breathing patterns at altitude, as well as on daytime attention, fatigue, and sleepiness. DESIGN: Double-blind, randomized, placebo-controlled, cross-over trial. SETTING: 3 day and night alpine expedition at 3,613 m altitude. PARTICIPANTS: 12 healthy male trekkers. PROCEDURE: One week spent at 1,000 m altitude (baseline control), followed by 3 periods of 3 consecutive treatment nights (N1-3) at altitude, to test 10 mg zolpidem, 10 mg zaleplon, and placebo given at 21:45. MEASURES: Sleep from EEG, actigraphy and sleep logs; overnight arterial saturation in oxygen (SpO2) from infrared oximetry; daytime attention, fatigue and sleepiness from a Digit Symbol Substitution Test, questionnaires, and sleep logs; acute mountain sickness (AMS) from the Lake Louise questionnaire. RESULTS: Compared to baseline control, sleep at altitude was significantly impaired in placebo subjects as shown by an increase in the amount of Wakefulness After Sleep Onset (WASO) from 17 +/- 8 to 36 +/- 13 min (P<0.05) and in arousals from 5 +/- 3 to 20 +/- 8 (P<0.01). Slow wave sleep (SWS) and stage 4 respectively decreased from 26.7% +/- 5.8% to 20.6% +/- 5.8% of total sleep time (TST) and from 18.2% +/- 5.2% to 12.4% +/- 3.1% TST (P<0.05 and P<0.001, respectively). Subjects also complained from a feeling of poor sleep quality combined with numerous 02 desaturation episodes. Subjective fatigue and AMS score were increased. Compared to placebo control, WASO decreased by approximately 6 min (P<0.05) and the sleep efficiency index increased by 2% (P<0.01) under zaleplon and zolpidem, while SWS and stage 4 respectively increased to 22.5% +/- 5.4% TST (P<0.05) and to 15.0% +/- 3.4% TST (P<0.0001) with zolpidem only; both drugs further improved sleep quality. No adverse effect on nighttime SpO2, daytime attention level, alertness, or mood was observed under either hypnotic. AMS was also found to be reduced under both medications. CONCLUSIONS: Both zolpidem and zaleplon have positive effects on sleep at altitude without adversely affecting respiration, attention, alertness, or mood. Hence, they may be safely used by climbers.     

Sleep and motor performance in on-call internal medicine residents

STUDY OBJECTIVES: To compare vigilance and performance among internal medicine residents doing in-house call versus residents not doing in-house call. DESIGN: Prospective study of resident cohorts with repeated testing. SETTING: University Teaching Hospital. PARTICIPANTS: Internal medicine residents doing in-house call and residents not doing in-house call (pathology, endocrinology) (controls). MEASUREMENTS AND RESULTS: Subjective sleepiness scores (daily Stanford Sleepiness Scale and Epworth Sleepiness Scale at start and end of the test period), actigraphy, and daily sleep logs as well as regular psychomotor vigilance testing using a Palm version (Walter Reed Army Institute of Research) of the Psychomotor Vigilance Test (PVT). Subjects were enrolled for a period of 28 to 32 days, which included 4 to 6 on-call nights for the internal medicine residents. Controls took call from home. Participants were compensated for their time. RESULTS: Twenty residents were evaluated, 13 internal medicine and 7 controls. Overall median reaction time was slower in the internal medicine residents (264.7 +/- 102.9 vs 239.2 +/- 26.1 milliseconds; P < .001). Internal medicine residents showed no difference in reaction time postcall versus other periods (269.9 +/- 131.2 vs 263.6 +/- 95.6; P = .65). Actigraphic sleep time was shorter during on-call than noncall nights and in internal medicine residents as compared with controls (287.48 +/- 143.8 vs 453.49 +/- 178.5 and 476.08 +/- 71.9 minutes; P < .001). Internal medicine residents had significantly greater major and minor reaction-time lapses compared with controls (1.26 +/- 3.4 vs 0.53 +/- 1.1 & 2.4 +/- 7.4 vs 0.45 +/- 1.0; P < .001). They reported increased sleepiness on postcall days compared with the start of their call (Stanford Sleepiness Scale: 3.26 +/- 1.2 vs 2.22 +/- 0.8; P < .001) but had scores similar to those of controls by their next call (2.22 +/- 0.8 vs 2.07 +/- 0.8; P = .13). CONCLUSIONS: Internal medicine residents have impaired reaction time and reduced vigilance compared with controls. Despite subjective improvements in sleepiness postcall, there was no change in their objective performance across the study period, suggesting no recovery. Internal medicine residents did not get extra sleep on postcall nights in an attempt to recover their lost sleep time. Implications for residents' well-being and patient care remain unclear.     

The effect of CPAP treatment on excessive daytime somnolence in patients with obstructive sleep apnea

The study was undertaken to investigate whether a CPAP therapy improves symptoms of excessive daytime sleepiness (EDS) in patients with obstructive sleep apnoea (OSA). In seventy six patients (66 M and 10 F) with AHI = 50 +/- 3.3, BMI = 34 +/- 0.9 kg/m2 and mean age = 50.4 +/- 1 years OSA was diagnosed using standard polysomnography. EDS was assessed using Epworth Sleepiness Scale (ESS). Each patient was examined two or three times, before, after 1 and/or 2-15 months of CPAP treatment. Significant reduction of EDS within 1 month of CPAP therapy was found. Mean ESS was reduced from 14.3 +/- 0.9 to 7.0 +/- 0.7 after 1 month therapy (p < 0.001). Continuation of treatment had no further effect on decrease of symptoms of daytime sleepiness. There was a correlation between percent of sleep spent with CPAP and improvement in ESS.     

Inter- and intra-individual variability in performance near the circadian nadir during sleep deprivation

The study purpose was to assess inter- and intra-individual variability in neurobehavioral function near the circadian nadir during sleep deprivation and conduct exploratory factor analyses to assess relationships among alertness and performance measures during sleep deprivation. Twenty-five healthy individuals (16 females) aged 18-25 years participated. Participants were sleep deprived for two nights under controlled laboratory conditions using a modified constant routine procedure. A comprehensive battery of neurobehavioral performance tests, subjective sleepiness (SSS), and objective alertness (MWT) were assessed. Seventeen of the 22 neurobehavioral measures were impaired by sleep deprivation (all P < 0.01). The use of multiple neurobehavioral performance measures revealed impairments for all individuals during sleep deprivation. However, sleep deprivation effects were task dependent within and between individuals. Gender contributed minimally to inter-individual variability in performance. Exploratory factor analysis reduced the 22 measures to seven independent factors. Our findings indicate that no individual was especially vulnerable or resistant to the performance impairing effects of sleep deprivation. Instead, inter- and intra-individual variability in performance during sleep deprivation was task dependent. The finding that subjective sleepiness and objective alertness were not related to any performance measure during sleep deprivation suggests that these measures may assess independent brain functions.     

Sleep behavior of South African adolescents

STUDY OBJECTIVES: To survey a large group of South African adolescents about their sleep behavior, daytime behaviors, and morning alertness as compared to those of other teenagers worldwide. DESIGN: Subjects completed a questionnaire about their sleep habits and daytime behaviors on the previous day, and subjective morning alertness at the time of completing the questionnaire. SETTING: Four secondary schools in Johannesburg, South Africa on mid-week mornings. PARTICIPANTS: 825 secondary school students volunteered for this study. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The students, (16+/-1 years), 61% female, reported significantly less time in bed (p<0.001) on a school night (453+/-70 minutes), compared to weekend nights (476+/-128 minutes). On the school night, they reported a mean sleep onset latency of 17 minutes, with 45% of the sample falling asleep in less than ten minutes. Short sleep onset latency and short in-bed wakefulness both were positively related to a high sleep efficiency and subjective sleep quality. On the previous day, 72% of the adolescents had consumed caffeinated beverages and 56% had exercised, but these behaviors did not significantly influence their nighttime sleep. The majority (77%) of students had napped the previous day and 8% had taken medication to fall asleep that night. 40% of the students felt that they could fall asleep mid-morning, if given the chance, but their sleepiness was independent of their nighttime sleep quality or duration. CONCLUSIONS: Similarly to teenagers around the world, South African adolescents get insufficient sleep during the week, which they attempt to compensate for on the weekends. A large proportion of the students are also sleepy during the school day, which may influence their academic performance.     

Daytime sleepiness and the COMT val158met polymorphism in patients with Parkinson disease

STUDY OBJECTIVE: A preliminary study by our group suggested an association between daytime sleepiness and the catechol-O-methyltransferase (COMT) val158met polymorphism (rs4680) in patients with Parkinson disease (PD). We sought to confirm this association in a large group of patients with PD. DESIGN: Genetic association study in patients with PD. SETTING: Movement disorder sections at 2 university hospitals. PARTICIPANTS: PD patients with and without episodes of suddenly falling asleep matched for antiparkinsonian medication, disease duration, sex, and age, who participated in a previous genetic study on dopamine-receptor polymorphisms. INTERVENTIONS: Not applicable. MEASUREMENTS AND RESULTS: In this study, 240 patients with PD (154 men; age 65.1 +/- 6.1 years; disease duration 9.4 +/- 6.0 years) were included. Seventy had the met-met (LL), 116 the met-val (LH), and 54 the val-val (HH) genotype. In the combined LL+LH group (featuring reduced COMT activity), the mean Epworth Sleepiness Scale (ESS) score was 9.0 +/- 5.9 versus 11.0 +/- 6.1 in the HH (high COMT activity) group (P = .047). Forty-seven percent of the LL and LH patients had sudden sleep onset compared with 61% of the HH patients (P = .07). Logistic regression, however, showed that both pathologic ESS scores (i.e., > 10) and sudden sleep onset were predicted by subjective disease severity (P < .001 each) but not by the COMT genotype. CONCLUSIONS: Our previous finding that the L-allele may be associated with daytime sleepiness could not be confirmed in the present study. Altogether, our data do not support a clinically relevant effect of the COMT genotype on daytime sleepiness in PD.     

Sensitivity and specificity of the multiple sleep latency test (MSLT), the maintenance of wakefulness test and the epworth sleepiness scale: failure of the MSLT as a gold standard

Excessive daytime sleepiness (EDS) is an important symptom that needs to be quantified, but there is confusion over the best way to do this. Three of the most commonly used tests: the multiple sleep latency test (MSLT), the maintenance of wakefulness test (MWT) and the Epworth sleepiness scale (ESS) give results that are significantly correlated in a statistical sense, but are not closely related. The purpose of this investigation was to help clarify this problem. Previously published data from several investigations were used to calculate the reference range of normal values for each test, defined by the mean+/-2 SD or by the 2.5 and 97.5 percentiles. The 'rule of thumb' that many people rely on to interpret MSLT results is shown here to be misleading. Previously published results from each test were also available for narcoleptic patients who were drug-free at the time and who by definition had EDS. This enabled the sensitivity and specificity of the three tests to be compared for the first time, in their ability to distinguish the EDS of narcolepsy from the daytime sleepiness of normal subjects. The receiver operator characteristic curves clearly showed that the ESS is the most discriminating test, the MWT is next best and the MSLT the least discriminating test of daytime sleepiness. The MSLT can no longer be considered the gold standard for such tests.