Subjective and objective indices of sleepiness (ESS and MWT) are not equally useful in patients with sleep apnea

Residual Sleepiness Risk in Aircrew Members with -Obstructive Sleep Apnea Syndrome

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is a major problem in aviation medicine because it is responsible for sleepiness and high cardiovascular risk, which could jeopardize flight safety. Residual sleepiness after the treatment is not a rare phenomenon and its management is not homogenous in aviation medicine. Thus, we decided to perform a study to describe this management and propose guidelines with the help of the literature.METHODS: This is a retrospective study including all aircrew members with a history of OSAS who visited our aeromedical center between 2011 and 2018. Residual sleepiness assessment was particularly studied.RESULTS: Our population was composed of 138 aircrew members (mean age 50.1 ± 9.6 yr, 76.8% civilians, 80.4% pilots); 65.4% of them had a severe OSAS with a mean Epworth Sleepiness Scale (ESS) at 8.5 ± 4.7 and a mean apnea hypopnea index of 36.2 ± 19.2/h. Of our population, 59.4% performed maintenance of wakefulness tests (MWT) and 10.1% had a residual excessive sleepiness. After the evaluation, 83.1% of our population was fit to fly.DISCUSSION: An evaluation of treatment efficiency is required in aircrew members with OSAS. Furthermore, it is important to have an objective proof of the absence of sleepiness. In this case, ESS is not sufficient and further evaluation is necessary. Many tests exist, but MWT are generally performed and the definition of a normal result in aeronautics is important. This evaluation should not be reserved to solo pilots only.Monin J, Rebiere E, Guiu G, Bisconte S, Perrier E, Manen O. Residual sleepiness risk in aircrew members with obstructive sleep apnea syndrome. Aerosp Med Hum Perform. 2023; 94(2):74-78.

Revisiting the Concept of Vigilance

Vigilance deficits can be observed after a period of prolonged, continuous wakefulness. In this context there has been extensive research targeting the impact of sleep deficits on different aspects of vigilance, but the underlying concept of vigilance was hardly ever addressed and discussed. One reason for this shortcoming is the unclear and ambiguous definition of the term vigilance, which is commonly used interchangeably with sustained attention and even wakefulness. This confusion is the result of a wide range of misleading definitions, starting in the 1940s, as psychologists redefined the concept of vigilance suggested by British Neurologist, Henry Head, in 1923. Nevertheless, the concept of vigilance is still useful and innovative, especially in treating sleep problems in children and young adults. This paper reviews the current usage of the term vigilance in sleep-wake-research and describes not only the benefits, but even more clearly, its limitations. By re-focusing on the definitions given by Henry Head, the concept of vigilance is an innovative way to gather new insights into the interplay between sleep- and daytime behaviors. In addition, future research on vigilance should consider three perspectives: 1st vigilance perceived as a process to allocate resources, 2nd vigilance associated with compensatory behaviors and 3rd the role of vigilance in human environmental interactions. This approach, understood as a conceptual framework, provides new perspectives by targeting sleep-wake behaviors as a 'real life' outcome measure, reflecting both physical and cognitive performance as well as sleep quality and quantity.

Microsleep versus Sleep Onset Latency during Maintenance Wakefulness Tests: Which One Is the Best Marker of Sleepiness?

The interpretation of the Maintenance Wakefulness Test (MWT) relies on sleep onset detection. However, microsleeps (MSs), i.e., brief periods of sleep intrusion during wakefulness, may occur before sleep onset. We assessed the prevalence of MSs during the MWT and their contribution to the diagnosis of residual sleepiness in patients treated for obstructive sleep apnea (OSA) or hypersomnia. The MWT of 98 patients (89 OSA, 82.6% male) were analyzed for MS scoring. Polysomnography parameters and clinical data were collected. The diagnostic value for detecting sleepiness (Epworth Sleepiness Scale > 10) of sleep onset latency (SOL) and of the first MS latency (MSL) was assessed by the area under the receiver operating characteristic (ROC) curve (AUC, 95% CI). At least one MS was observed in 62.2% of patients. MSL was positively correlated with SOL (r = 0.72, p < 0.0001) but not with subjective scales, clinical variables, or polysomnography parameters. The use of SOL or MSL did not influence the diagnostic performance of the MWT for subjective sleepiness assessment (AUC = 0.66 95% CI (0.56, 0.77) versus 0.63 95% CI (0.51, 0.74)). MSs are frequent during MWTs performed in patients treated for sleep disorders, even in the absence of subjective sleepiness, and may represent physiological markers of the wake-to-sleep transition.

Emerging applications: Screening OSA by Modified Pictorial Epworth Sleepiness Scale in Indian subjects

BACKGROUND

The Epworth Sleepiness Scale (ESS) is a widely used scoring to measure excessive daytime sleepiness. This scale was designed to be self-completed by the subjects, but unfortunately in a developing country with low literacy this had affected its outcome interpretation. The Traditional ESS has been translated into a Modified Pictorial version for easy comprehension by the patients.

METHOD

Subjects were evaluated for their competence to self-complete the ESS (Conventional and Pictorial) in Sleep Clinic at Respiratory Department of Santosh Medical College and Hospital, Ghaziabad. Modified Pictorial representations were designed along with 5 newer questions incorporated as sub-questions in 8 original domains prepared and labelled as Pictorial Scale. The Traditional (ESS) and Pictorial (Modified) representations were compared for agreement by receiver operating curve and the area under curve.

RESULTS

It was found that time taken to complete the Traditional ESS was significantly higher in comparison to Modified Pictorial Epworth Sleepiness Scale with reduced errors (Pictorial ESS 4.67min than Traditional ESS 14.43min).

CONCLUSIONS

Modified pictures scale showed statistically significant improvements over ESS and hence can be used as an alternative for subjects with low literacy level.

The Barcelona Sleepiness Index: A New Instrument to Assess Excessive Daytime Sleepiness in Sleep Disordered Breathing

STUDY OBJECTIVES

To develop the Barcelona Sleepiness Index (BSI), an interviewer-administered instrument for assessing excessive daytime sleepiness (EDS) in sleep-disordered breathing (SDB) that correlates well with objective measures of EDS and which is sensitive to change with treatment.

METHODS

(1) Generation of a preliminary item list: Fifty-three consecutive SDB patients complaining of EDS and their bed partners were interviewed using a focus group methodology to generate a list of situations prone to cause sleepiness. Sixty different consecutive SDB patients were then evaluated using cognitive interviews to refine this list. (2) Construct validity: The maintenance of wakefulness test (MWT), the multiple sleep latency test (MSLT) and the sustained attention to response task (SART) test were used in an additional 98 consecutive SDB patients with and without EDS. The item combination that best correlated with the objective tests constituted the BSI. Cutoff values were determined to differentiate between patients with and without EDS. (3) Sensitivity to change: Thirty patients requiring continuous positive airway pressure (CPAP) were evaluated after satisfactory treatment.

RESULTS

A combination of two items, "in the morning, when relaxing" and "in the afternoon, standing inactive, in a public place," presented the highest correlations with the MWT (r: -0.50, p < 0.001), the MSLT (r: -0.21, p = 0.07), and the SART (r: 0.27, p < 0.02) and constituted the BSI. The BSI significantly correlated with oxyhemoglobin saturation measures (nadir SpO2: r: -0.28, p = 0.01; CT 85: r: 0.23, p = 0.04) and showed a high sensitivity to change with CPAP treatment (t: 3.4, p = 0.002). A score of 2 or more identified patients with objective EDS (sensitivity = 64.9%, specificity = 72.1%).

CONCLUSION

The Barcelona Sleepiness Index is a simple, brief instrument for measuring subjective EDS in SDB.

End of OSLER Test Sessions in Parkinson’s Disease do not Correspond to True Sleep Onset: Results from an Exploratory Study

The aim of the present study was to evaluate the correlation between the end of an Oxford sleep resistance (OSLER) test session and a neurophysiological marker of sleep onset in Parkinson’s disease (PD) patients. Single center study was conducted in PD patients with excessive daytime sleepiness [Epworth sleepiness scale (ESS) >9]. The OSLER test was conducted with a concomitant electroencephalography (EEG), electromyography (mentalis), right and left electroculogram, and video monitoring. Neurophysiological (NP) sleep onset was defined according to AASM criteria (2005). Five PD patients with mean ESS of 14 (10–16) were included. OSLER test duration was shorter than 40 min in all patients (mean duration 20 min and 39 s). No patient fulfilled neurophysiological criteria to sleep onset at the time of OSLER test termination. In 13 OSLER sessions that ended before 40 min, eight had microsleeps in the last 30 s before the end of the test. NP monitoring showed signs of sleepiness in all patients. In PD patients, the early termination of an OSLER test session may not correspond to NP criteria of sleep onset. However, in all PD patients with abnormal OSLER results, there were EEG signs of sleepiness, which do not exclude the potential utility of OSLER test to evaluate the risk of falling asleep.

Impact of rail medical standard on obstructive sleep apnoea prevalence

BACKGROUND

The 2004 edition of the National Standard for Health Assessment of Rail Safety Workers (the standard) used the Epworth Sleepiness Scale (ESS) to screen for excessive daytime sleepiness related to obstructive sleep apnoea (OSA). The 2012 edition of the standard expanded the OSA screening matrix to include body mass index, comorbid hypertension and type 2 diabetes as triggers requiring a sleep study to be undertaken irrespective of the ESS.

AIMS

To assess the impact of the new standard on the estimated prevalence of OSA in railway workers.

METHODS

An analysis of data on safety critical employees referred for rail safety health assessment during the 2013 calendar year and meeting the criteria for sleep study referral. Sleep study outcomes were used to assess the predictive value of screening under the new standard.

RESULTS

A total of 200/4311 workers were investigated with a sleep study. One hundred and ninety-three met the new risk factor criteria and 182 (91%) were newly diagnosed with OSA. The prevalence of OSA in the study population was 7%, compared with 2% in 2009. No worker reported an elevated ESS. The false positive to true positive ratio was 0.1 (95% CI 0.06-0.16).

CONCLUSIONS

The new medical standard has resulted in an increased estimate of the prevalence of OSA in rail workers. This study supports the use of objective clinical risk factors to select workers for further investigation, aiming to minimize the risk of accidents associated with excessive daytime sleepiness and other comorbid conditions of OSA.

Measurement properties of patient-reported outcome measures (PROMs) in adults with obstructive sleep apnea (OSA): A systematic review

This systematic review summarizes the evidence regarding the quality of patient-reported outcome measures (PROMs) validated in patients with obstructive sleep apnea (OSA). We performed a systematic literature search of all PROMs validated in patients with OSA, and found 22 measures meeting our inclusion criteria. The quality of the studies was assessed using the consensus-based standards for the selection of health status measurement instruments (COSMIN) checklist. The results showed that most of the measurement properties of the PROMs were not, or not adequately, assessed. For many identified PROMs there was no involvement of patients with OSA during their development or before the PROM was tested in patients with OSA. Positive exceptions and the best current candidates for assessing health status in patients with OSA are the sleep apnea quality of life index (SAQLI), Maugeri obstructive sleep apnea syndrome (MOSAS) questionnaire, Quebec sleep questionnaire (QSQ) and the obstructive sleep apnea patient-oriented severity index (OSAPOSI). Even though there is not enough evidence to fully judge the quality of these PROMs as outcome measure, when interpreted with caution, they have the potential to add value to clinical research and clinical practice in evaluating aspects of health status that are important to patients.

Effect of oral JZP-110 (ADX-N05) treatment on wakefulness and sleepiness in adults with narcolepsy

BACKGROUND

JZP-110 is a wake-promoting agent with dopaminergic and noradrenergic activity.

METHODS

This double-blind, crossover study, randomized adults with narcolepsy with or without cataplexy (N = 33) to placebo or JZP-110 at 150 mg/day (weeks 1 and 3) increased to 300 mg/day (weeks 2 and 4). Patients had to have baseline Epworth Sleepiness Scale (ESS) scores ≥10 and mean sleep latencies ≤10 min on the Maintenance of Wakefulness Test (MWT). Efficacy end points included MWT sleep latency and ESS, and the percentage of patients improved on the Clinical Global Impression of Change.

RESULTS

Patients were primarily male (57.6%) and white (69.7%), with a mean (standard deviation) age of 37.1 (12.4) years. At two weeks, the change in the mean MWT sleep latency was 11.8 min longer with JZP-110 than with placebo (P = 0.0002); JZP-110 resulted in greater changes in sleep latency on each MWT trial (P <0.001). For ESS, JZP-110 was more efficacious relative to placebo after 1 (P <0.0001) and two weeks (P = 0.0002); final ESS scores were 10.8 with JZP-110 and 15.2 with placebo, changes of -6.7 and -2.4, respectively. JZP-110 was generally well tolerated; the most common adverse events with JZP-110 were nausea (12%), noncardiac chest discomfort (9.1%), and headache (9.1%).

CONCLUSIONS

The efficacy of JZP-110 for impaired wakefulness and excessive sleepiness was observed at 150-300 mg/day and as early as one week after initiating treatment (Clinicaltrials.gov identifier NCT01485770).

The Oxford Sleep Resistance test (OSLER) and the Multiple Unprepared Reaction Time Test (MURT) detect vigilance modifications in sleep apnea patients

STUDY OBJECTIVES

The Oxford Sleep Resistance Test (OSLER) is a behavioral test that measures a subject's ability to maintain wakefulness and assesses daytime vigilance. The multiple unprepared reaction time (MURT) test measures a subject's reaction time in response to a series of visual or audible stimuli.

METHODS

We recruited 34 healthy controls in order to determine the normative data for MURT. Then we evaluated modifications in OSLER and MURT values in 192 patients who were referred for suspicion of sleep apnea. We performed OSLER (three 40-min sessions) and MURT (two 10-min sessions) tests at baseline. Of 173 treated OSA patients, 29 professional drivers were retested within six months of treatment.

RESULTS

MURT values above 250 ms can be considered abnormal. The OSLER error index (the number of all errors divided by the duration of the session in hours) correlated statistically significantly with sleep latency, MURT time, and ESS. Treatment improved OSLER sleep latency from 33 min 4 s to 36 min 48 s, OSLER error index from 66/h to 26/h, and MURT time from 278 ms to 224 ms; these differences were statistically significant.

CONCLUSIONS

OSLER and MURT tests are practical and reliable tools for measuring improvement in vigilance due to sleep apnea therapy in professional drivers.

Epworth sleepiness scale scores and adverse pregnancy outcomes

PURPOSE

Snoring is associated with adverse pregnancy outcomes including gestational hypertensive disorders, gestational diabetes, and Cesarean deliveries. The purpose of this study was to assess whether excessive daytime sleepiness (EDS) assessed by Epworth Sleepiness Scale (ESS) increases the risk of these complications further.

METHODS

Following institutional review board approval and informed consent, English-speaking women in the immediate postpartum period were systematically selected and recruited. Women answered a survey that included questions regarding symptoms of sleep-disordered breathing (SDB) using the multivariable apnea prediction index and excessive daytime sleepiness using ESS. Pregnancy and fetal outcomes were collected by review of medical records. Standard statistical analysis with multivariable logistic regression was performed. ESS was evaluated both as a continuous variable and with various cutoffs given that pregnant women are likely more sleepy at baseline than the general population.

RESULTS

In patients who underwent planned Cesarean delivery, mean ESS was significantly higher than in those with uncomplicated vaginal delivery, even after adjusting for confounders (adjusted odds ratio (aOR), 1.08; 95 % CI, 1.01-1.15; p = 0.02). There was no significant association between EDS (defined as ESS of >10) and gestational diabetes or gestational hypertensive disorders in snorers or non snorers. However, a significant association with gestational diabetes was found in patients with an ESS of >16 compared to those with an ESS of ≤16, even after multiple adjustments (aOR, 6.82; 95 % CI, 1.19-39.27), but the number of subjects in an ESS of >16 category was small.

CONCLUSIONS

There is an increased association between women with higher ESS and planned Cesarean delivery. Severe EDS was associated with gestational diabetes in pregnant women in a small sample size. Future studies in larger samples need to confirm the association of severe EDS and gestational diabetes and elucidate potential mechanisms of the links with adverse outcomes.

Evaluating sleepiness-related daytime function by querying wakefulness inability and fatigue: Sleepiness-Wakefulness Inability and Fatigue Test (SWIFT)

STUDY OBJECTIVES

Routine assessment of daytime function in Sleep Medicine has focused on "tendency to fall asleep" in soporific circumstances, to the exclusion of "wakefulness inability" or inability to maintain wakefulness, and fatigue/tiredness/lack of energy. The objective was to establish reliability and discriminant validity of a test for wakefulness inability and fatigue, and to test its superiority against the criterion standard for evaluation of sleepiness-the Epworth Sleepiness Scale (ESS).

METHODS

A 12-item self-administered instrument, the Sleepiness-Wakefulness Inability and Fatigue Test (SWIFT), was developed and administered, with ESS, to 256 adults ≥ 18 years of age (44 retook the tests a month later); consecutive patients with symptoms of sleep disorders including 286 with obstructive sleep apnea ([OSA], apnea-hypopnea index ≥ 5/h sleep on polysomnography [PSG]), 49 evaluated with PSG and multiple sleep latency test for narcolepsy and 137 OSA patients treated with continuous positive airway pressure (CPAP).

RESULTS

SWIFT had internal consistency 0.87 and retest intraclass coefficient 0.82. Factor analysis revealed 2 factors-general wakefulness inability and fatigue (GWIF) and driving wakefulness inability and fatigue (DWIF). Normal subjects differed from patients in ESS, SWIFT, GWIF, and DWIF. SWIFT and GWIF (but not DWIF) had higher area under ROC curve, Youden's index, and better positive and negative likelihood ratios than ESS. ESS, SWIFT, GWIF, and DWIF improved with CPAP. Improvements in SWIFT, GWIF, and DWIF (but not ESS) were significantly correlated with CPAP compliance.

CONCLUSIONS

SWIFT is reliable and valid. SWIFT and its factor GWIF have a discriminant ability superior to that of the ESS.

Scales to assess sleep impairment in Parkinson's disease: critique and recommendations

There is a broad spectrum of sleep disturbances observed in Parkinson's disease (PD). A variety of scales have been applied to the evaluation of PD sleep and wakefulness, but only a small number have been assessed specifically for clinimetric properties in the PD population. The movement disorder society has commissioned this task force to examine these scales and to assess their use in PD. A systematic literature review was conducted to explore the use of sleep scales in PD and to determine which scales qualified for a detailed critique. The task force members, all of whom have extensive experience in assessing sleep in PD reviewed each of the scales using a structured proforma. Scales were categorized into recommended, suggested and listed according to predefined criteria. A total of 48 potential scales were identified from the search and reviewed. Twenty-nine were excluded because they did not meet review criteria or were variations of scales already included, leaving 19 scales that were critiqued and rated by the task force based on the rating criteria. Only six were found to meet criteria for recommendation or suggestion by the task force: the PD sleep scale (PDSS) and the Pittsburgh sleep quality index (PSQI) are recommended for rating overall sleep problems to screen and to measure severity, the SCOPA-sleep (SCOPA) is recommended for rating overall sleep problems both to screen and to measure severity, and for rating daytime sleepiness; the Epworth sleepiness scale (ESS) is recommended for rating daytime sleepiness to screen and to measure severity; the inappropriate sleep composite score (ISCS) is suggested for rating severe daytime sleepiness or sleep attacks to screen and to measure severity; and the Stanford sleepiness scale (SSS) is suggested for rating sleepiness and to measure severity at a specific moment. The task force does not recommend the development of new scales, but emphasizes the need for educational efforts to train physicians in sleep interview techniques and polysomnography.

Executive functions and cognitive subprocesses in patients with obstructive sleep apnoea

In recent years, special interest has been focused on impairments of executive functions in patients with obstructive sleep apnoea syndrome (OSAS). However, the majority of studies have not clearly separated deficits in executive functions from impairments in other cognitive processes involved in task solving. In the present study, working memory (WM) functions of 20 patients with OSAS were compared with those of 10 age-, sex- and education-matched healthy subjects. Cognitive functions were measured four times a day; each of these measurements was accompanied by an assessment of subjective and objective daytime sleepiness. To separate dysfunctions of WM from those of additionally involved processes, n-back tasks were applied embedded in a reaction-time-decomposition approach. Deficits in n-back tasks could be observed in OSAS patients in accuracy and reaction times. However, the slowing could already be observed in simple reaction time tasks. The drop in 1-back accuracy in the morning was related to daytime sleepiness. During the afternoon, accuracy of OSAS patients dropped in 2-back tasks, an effect which correlated neither with sleepiness nor with the extent of sleep apnoea or oxygen desaturation. In conclusion, our data reflect a complex perspective upon cognitive deficits in OSAS. Cross-group differences in processing time on the higher level WM task appeared to be attributable to slowing at a more elementary cognitive processing level. In contrast, reduced accuracy during the WM task in the OSAS group could not be explained by deficits in more elementary cognitive processes.

Factors influencing subjective sleepiness in patients with obstructive sleep apnea syndrome

The aim of the present paper was to clarify the factors influencing subjective daytime sleepiness in patients with obstructive sleep apnea syndrome (OSAS). Subjects included 230 adult male OSAS patients aged 20-73 years. Single and multiple linear regression analyses were performed to estimate the association between the Epworth Sleepiness Scale (ESS) and the following variables: Minnesota Multiphasic Personality Inventory (MMPI), Self-Rating Depression Scale (SDS), age, body mass index (BMI), sleep duration during the preceding month and apnea-hypopnea index (AHI). Single linear regression analysis showed that age had a negative association with ESS score, while BMI, AHI, SDS, hypochondriasis (Hs), hysteria, psychopathic deviant, psychasthenia, schizophrenia and hypomania on the MMPI had a positive association with ESS score. However, the other remaining parameters such as nocturnal sleep duration during the preceding month, depression, masculinity-femininity, paranoia, social introversion on the MMPI had no statistical association with ESS score. Multiple linear regression analysis with stepwise elimination method was applied to choose the significant factors associated with ESS. It was found that three variables including age, AHI and Hs scores were independent factors influencing ESS score. The R(2) for the model was 0.14, suggesting that these factors account for 14% of possible variance of subjective daytime sleepiness of OSAS patients. These results suggest that subjective daytime sleepiness in patients with OSAS may be influenced not only by the severity of respiratory disorder indices but also by certain personality characteristics affecting Hs score and by age.

Reciprocal interactions between spontaneous and respiratory arousals in adults with suspected sleep-disordered breathing

BACKGROUND AND PURPOSE

Excessive daytime sleepiness (EDS) is a major consequence of sleep-disordered breathing (SDB) in adults. In snoring children, spontaneous and respiratory arousals display reciprocal interactions, allowing for development of a new quantitative measure, the sleep pressure score (SPS), which provides intra-polysomnographic estimates of sleep pressure/disruption. The aim of the present study was to assess the interactions between respiratory and spontaneous arousals in adults with suspected SDB, and to examine whether the SPS and the Epworth sleepiness scale (ESS) are correlated.

PATIENTS AND METHODS

Retrospective chart review of 530 adult patients who underwent polysomnographic evaluation for suspected SDB in two medical centers was performed. Polysomnographic studies reports, patients' demographics and ESS scores were reviewed.

RESULTS

Spontaneous and respiratory arousal indices and the apnea-hypopnea index (AHI) displayed negative and positive correlations respectively (r=-0.25, r=0.97, P<0.0001) indicating reciprocal interactions between respiratory and spontaneous arousals during sleep. The AHI corresponding to the SPS at which the respiratory arousal/total arousal fraction exceeded the spontaneous arousal/total arousal fraction occurred at approximately 14/h of total sleep time (TST) (compared to 7/h TST in children) (P<0.001). No correlation was found between SPS values and ESS scores.

CONCLUSIONS

As in children, snoring adults exhibit reciprocal interactions between respiratory and spontaneous arousals that can also be expressed as a single quantitative measure, the SPS, which is highly dependent on the severity of SDB and could possibly serve as a more reliable index of sleep disruption, considering that the ESS is unrelated to either SPS or AHI.

Distinguishing sleepiness and fatigue: focus on definition and measurement

Sleepiness and fatigue are two interrelated, but distinct phenomena; observed in a number of psychiatric, medical and primary sleep disorders. Despite their different implications in terms of diagnosis and treatment, these two terms are often used interchangeably, or merged under the more general lay term of 'tired'. Sleepiness is multidimensional and has many causes (multidetermined) and distinguished from fatigue by a presumed impairment of the normal arousal mechanism. Despite its ubiquity, no clear consensus exits as yet as to what constitutes sleepiness. Definitions of sleepiness, to date, are at best operational definitions, conceptualized so as to produce specific assessment instruments. As a result, while a number of subjective and objective measurement tools have been developed to measure sleepiness, each only captures a limited aspect of an otherwise heterogeneous entity. Fatigue is an equally complex phenomenon, its nature captured by a number of conceptualizations and definitions. Measures of fatigue have remained subjective, with a 'gold standard' for its measurement remaining elusive. Despite a high prevalence and high degree of morbidity, fatigue has remained a relatively under appreciated symptom, from both a clinical and research point of view.

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.

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.

Sleepiness and residual sleepiness in adults with obstructive sleep apnea

Sleepiness is a common, but not necessary symptom of the obstructive sleep apnea syndrome (OSA) and is a frequent chief complaint of patients with OSA who seek medical attention. While sleepiness may seem simple in nature, the underlying mechanisms producing daytime sleepiness in OSA are complex and poorly characterized. Moreover, the meaningful assessment of pathological sleepiness is frequently far from straightforward. Effective treatment of OSA is generally expected to resolve or ameliorate daytime sleepiness. An unknown percentage of treated OSA patients, however, remain sleepy during waking hours. The assessment and treatment of residual sleepiness in treated OSA can range from simple to difficult, depending on the nature and causes of the continued sleepiness. Recently, however, data from clinical trials have been generated which provide direction in the evaluation and management of the OSA patient suffering residual daytime sleepiness.

The physiologic impact of sleep apnea on wakefulness

The physiologic impact of sleep apnea on wakefulness is believed to be mediated by sleep fragmentation secondary to airway obstruction. Although there has been much study on the association between sleep apnea and daytime sleepiness, little is known about the effects of sleep apnea on non-sleepiness-related manifestations of impaired wakefulness, such as fatigue and depression. Present studies suggest that impaired wakefulness secondary to sleep apnea probably plays a contributory role in traffic and industrial accidents.

The assessment of daytime sleep propensity: a comparison between the Epworth Sleepiness Scale and a newly developed Resistance to Sleepiness Scale

INTRODUCTION

The Epworth sleepiness scale (ESS) is widely used as a way of measuring subjective sleep propensity in research and clinical practice. Psychometric studies do not rule out the presence of more than one latent dimension underlying the items.

OBJECTIVE

Aims of the present study were to: (a) evaluate psychometric proprieties of the ESS by means of classic psychometric techniques; (b) compare them with those from a newly developed resistance to sleepiness scale (RSS); (c) evaluate, following the latent trait theory, whether the items of both ESS and RSS could be conceptualized as different levels of an interval variable representative of a single latent trait related to sleep propensity.

METHODS

One hundred and forty-six inpatients suffering from different sleep disorders filled in both the RSS and ESS in a sleep disorder centre.

RESULTS

Indexes of fit derived by the application of the extended logistic model are consistent with the idea that each ESS item can be conceptualized as different levels of an interval variable representative of a single latent trait. However, most of the ESS items are found to be located at the opposite extremes of this continuum.

CONCLUSIONS

The under representation of situations characterized by an intermediate soporific nature in the ESS could limit ESS sensitivity to detect intermediate variations of sleep propensity.

Analysis of error profiles occurring during the OSLER test: a sensitive mean of detecting fluctuations in vigilance in patients with obstructive sleep apnea syndrome

The OSLER test represents a simple alternative to the maintenance of wakefulness test. Standard analysis of OSLER test results yields a mean sleep latency (MSL). The aim of this study was to use both MSL and errors (nonresponses to stimulations) to characterize daytime sleepiness in apneic patients. OSLER test results at 9:00 A.M., 11:00 A.M. and 1:30 P.M. were compared in 27 obstructive sleep apnea syndrome patients (50.4 +/- 10.4 years; apnea-hypopnea index: 43.05 +/- 25.08) and 20 control subjects (C). Not only did obstructive sleep apnea syndrome patients demonstrate earlier sleep onset than control subjects (MSL: 1,788 seconds +/- 511 versus 2,335 seconds +/- 139, p < 0.001), but they also spent a greater percentage of time making errors than control subjects (5.4% +/- 4.7 of total test time versus 0.4% +/- 0.4, p < 0.001) with specific error profiles (high prevalence of three to six consecutive errors). When error profile analysis was added to standard sleep latency assessment, up to 40% of patients with normal sleep latency were exhibiting abnormal fluctuation in vigilance. A single 9:00 A.M. OSLER session appeared as sensitive as three consecutive sessions in its use as a means of identifying patients with significant daytime sleepiness. On the other hand, the 1:30 P.M. OSLER test session was least specific to distinguish apneic subjects from normal subjects, suggesting that the OSLER test can identify the afternoon peak in physiologic somnolence.

Microsleep during a simplified maintenance of wakefulness test. A validation study of the OSLER test

Daytime somnolence is both a symptom in many patients and a prevalent complaint in the general population, but its objective assessment remains elusive. The current available tests are technically complex and thus inadequate for routine clinical use or epidemiological studies. A simplified behavioral maintenance of wakefulness test (OSLER test) has been recently described that could allow for widespread availability of objective measurements of this symptom. We verified the occurrence of (micro)sleep (episodes of sleep of > or = 3 s duration) during the performance of the OSLER test in 10 normal subjects after a non-sleep-deprived night and a sleep-deprived night in randomized order. Sleep was assessed electrophysiologically according to standard methods. The OSLER test (mean of four measurements) was significantly shorter after the sleep-deprived night (25 min versus 38 min). Single missed stimuli were frequent with or without (micro)sleep, but (micro)sleep was almost always present when four or more consecutive stimuli were missed. The sensitivity and specificity of the test in detecting sleep (of > or = 3 s duration) are 85% and 94%, respectively. The total number of missed stimuli per minute duration of the test could add valuable information to the simpler mean test result. Sensitivity and specificity are not altered when only three measurements are performed. We conclude that the OSLER test appears as a simple, easy, and reliable method to objectively assess daytime somnolence.

Visual P300 latency predicts treatment response to modafinil in patients with narcolepsy

OBJECTIVE

To evaluate the hypothesis that visual P300 latency (VL) predicts treatment response to modafinil (a new wake-promoting agent) in patients with narcolepsy.

METHODS

DESIGN

Comparison of responders and non-responders in a double-blind randomized placebo-controlled trial.

SETTING

Private practice referral sleep disorders center.

PATIENTS

Twenty one patients with narcolepsy (ages 17-65 years).

INTERVENTIONS

Auditory and visual P300 testing using 31 evenly spaced scalp electrodes, and baseline polysomnograms and objective and subjective tests of daytime sleepiness, followed by modafinil treatment for 9 weeks. Polysomnograms and tests of sleepiness were then repeated.

MAIN OUTCOME MEASURE

The Maintenance of Wakefulness Test (MWT). Response defined as a final MWT > 7.3min (normative sample mean - 3 SD), plus an increase > 1SD based on normative sample (3.6 min) over baseline MWT.

RESULTS

Non-responders had longer age-adjusted 31-electrode mean VL (448.4 ms vs. 410.8 ms, P = 0.024), and larger auditory P300 amplitude, with no topographical P300 differences. Non-responders and responders did not differ on any other baseline clinical variable. Using a cut-off of 0.5 SE from normal regression constant, shorter age-adjusted VL predicted modafinil response, with specificity of 0.71 and sensitivity of 0.86.

CONCLUSIONS

VL predicts treatment response to modafinil in patients with narcolepsy.