REM sleep episodes during the maintenance of wakefulness test in patients with sleep apnea syndrome and patients with narcolepsy

Metabolic Profile in Patients with Mild Obstructive Sleep Apnea

BACKGROUND

Mild obstructive sleep apnea (OSA) is a highly prevalent disorder in adults. However, it is not clear whether mild OSA has significant metabolic complications. This study examined the prevalence of metabolic syndrome (MS) in patients with mild OSA compared to control group.

METHODS

Adults (18-65 years of age) of both genders with a body mass index (BMI) ≤35 kg/m² were included. The mild OSA group comprised of patients with an apnea-hypopnea index (AHI) score of ≥5 but ≤15 events/hr of sleep, independent of other symptoms. The control group (CG) comprised individuals with an AHI of <5 events/hr of sleep and an Epworth Sleepiness Scale score of <10. The following were used for both groups: two questionnaires on sleepiness, the maintenance of wakefulness test, and full-night polysomnography. Anthropometric measurements and fasting blood samples were obtained, including fasting glucose and insulin, total cholesterol and its subfractions [low-density lipoprotein, very low-density lipoprotein, and low-density lipoprotein cholesterol (HDL-c)], triglycerides (TG), and the TG/HDL-c ratio. In addition, the quantitative insulin sensitivity check index and homeostasis model assessment indices were calculated.

RESULTS

Thirty-two percent of mild OSA patients had MS, 43.5% of mild OSA patients had hypertension, 14% showed dyslipidemia, and 56% had prediabetes. The OSA group showed increased TG (CG: 90.0 ± 51.9 vs. OSA: 140.3 ± 78.2 mg/dL, P = 0.004), and TG/HDL-c (CG: 1.9 ± 1.4 vs. OSA: 3.1 ± 2.0, P = 0.05), independent of adjustments. Independent of obesity (BMI <30 kg/m²), there was a negative correlation between total cholesterol and TG with mean oxygen saturation, independent of obesity (BMI <30 kg/m²).

CONCLUSIONS

Our findings showed dysregulation in lipid profiles after adjustments for confounders in the mild OSA group, and there was a correlation between these parameters and sleep hypoxemia. The TG/HDL-c ratio in particular was high, suggesting that it might be investigated as a marker of a detrimental metabolic profile in these patients.

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.

CSF hypocretin measures in patients with obstructive sleep apnea

The majority of patients with narcolepsy-cataplexy were reported to have very low cerebrospinal fluid (CSF) hypocretin-1 (orexin-A) levels. The hypocretin-1 levels of secondary excessive daytime sleepiness (EDS) disorders are not known. In this study, we found that CSF hypocretin levels in the patients with obstructive sleep apnea syndrome were within the control range. The low hypocretin levels seem to reflect only the presence of cataplexy and DR2 positive in narcoleptics but not EDS itself.

Assessment of sleepiness in children

Excessive sleepiness is a common but under-recognized problem in children. This article examines the clinical and laboratory evaluation of sleepiness in children, including the use of polysomnography, the multiple sleep latency test, and other varieties of neurophysiologic testing. Where applicable, technical aspects of laboratory testing are reviewed. Alternative laboratory and neurobehavioral techniques used to investigate daytime sleepiness are also briefly covered.

Outcome measurement in sleep medicine practice and research. Part 1: assessment of symptoms, subjective and objective daytime sleepiness, health-related quality of life and functional status

The documentation of treatment outcomes has gained increased importance as those responsible for paying for healthcare focus on the delivery of cost-effective care. The practitioner and researcher, challenged with documenting the clinical significance of their endeavors, must depend on conceptually appropriate, valid and reliable instruments. Outcomes of particular relevance for sleep disorders include self-reported general symptoms, subjective and objective daytime sleepiness, neurobehavior, health-related quality of life (HRQL) or functional status, incidence of accidents and cardiovascular morbidity, and health care utilization and cost. This paper will limit its focus to the outcomes of self-reported general symptoms, subjective and objective daytime sleepiness, and HRQL or functional status. In addition to describing measures that could be applied to evaluate these outcomes, this paper will also discuss factors affecting the selection of outcome measures for use in research and practice, and consider evidence generated with the application of these instruments in research. Reductions in self-reported symptoms, such as snoring and daytime hypersomnolence following treatment, have been documented with the application of measures with strong psychometric properties such as the Survey Screen for Sleep Apnea and Epworth Sleepiness Scale. In addition to statistical reliability, calculation of the effect size and standardized response mean indicate that these changes are also clinically meaningful. Similar improvements have also been demonstrated using the Multiple Sleep Latency Test (MSLT), although the resulting increased latency has not typically been within normal values. Important improvements following treatment have been documented with the Maintenance of Wakefulness Test (MWT). Evidence suggests that the MWT may be more sensitive in situations, such as narcolepsy, where there are high levels of physiologic sleepiness, reserving the MSLT where the physiologic sleep tendency is more restricted, such as in obstructive sleep apnea (OSA). Patients>> perceptions of the benefit of treatment to their daily lives have been documented by such generic measures of HRQL, such as the SF-36 and Nottingham Health Profile. However, the impact of sleep disorders and the benefit of treatment on those aspects of daily behavior likely to be most affected have more clearly been demonstrated with the utilization of disease-specific HRQL measures such as the Functional Outcomes of Sleep Questionnaire and the Calgary Sleep Apnea Quality of Life Index. 2001 Harcourt Publishers Ltd

Narcolepsy and idiopathic hypersomnolence

Narcolepsy is among the leading causes of excessive daytime sleepiness. Its classic form associates daytime sleepiness with cataplexy, sleep paralysis, hypnopompic hallucinations, and nocturnal disrupted sleep. This form is associated with HLA DQ betal-0602 in about 85% to 90% of affected subjects, independently of their ethnicity. But the definition of the variants of narcolepsy remains controversial, despite the fact that, in some cases, narcolepsy may be limited to daytime sleepiness. In its classic form, it is associated with two or more sleep onset rapid eye movement periods at the Multiple Sleep Latency Test. This test, performed after nocturnal polysomnography, can be helpful in diagnosing narcolepsy, in the absence of a convincing history of partial or complete attacks of cataplexy--a pathognomonic symptom. Investigation of narcoleptic Dobermans has indicated that a muscarinic cholinergic hypersensitivity exists in the brain of affected animals and abnormalities involve also the dopaminergic system. Despite its prevalence of 0.03% to 0.05%, it is still a neurologic entity often missed. Investigations of families of narcoleptics, including monozygotic twins, indicate that this syndrome is polygenic in nature with association of environmental factors. As the peak of onset of disabling symptoms occurs between 15 and 25 years of age, it is important to improve the treatment of this lifelong, disabling illness. Stimulants medications, independently of their mode of action, are prescribed to help daytime sleepiness, and tricyclic antidepressant drugs or serotonergic reuptake blockers are used on the other symptoms. But these medications have a limited efficacy. Short naps at regular intervals during the day are a strong therapeutic adjuvent.

A normative study of the maintenance of wakefulness test (MWT)

The maintenance of wakefulness test (MWT) is a daytime polysomnographic procedure which quantifies wake tendency by measuring the ability to remain awake during soporific circumstances. We present normative data based on 64 healthy subjects (27 males and 37 females) who adhered to uniform MWT procedural conditions including polysomnographic montage, illuminance level, seating position, room temperature, meal timing, and subject instructions. When allowed a maximum trial duration of 40 min, subjects' mean sleep latency to the first epoch of sustained sleep was 35.2 +/- 7.9 min. The lower normal limit, defined as two standard deviations below the mean, was 19.4 min. Calculation of data on the basis of a maximum trial duration of 20 min and sleep latency to the first appearance of brief sleep (a microsleep episode or one epoch of any stage of sleep) yielded a mean sleep latency of 18.1 +/- 3.6 min and a lower normal limit of 10.9 min. Sleep latency scores were significantly higher than those previously reported in patients with disorders of excessive somnolence. Therefore, the MWT appears to be a useful procedure in differentiating groups with normal daytime wake tendency from those with impaired wake tendency and in identifying individuals with pathologic inability to remain awake under soporific circumstances.

P300 latency: abnormal in sleep apnea with somnolence and idiopathic hypersomnia, but normal in narcolepsy

To evaluate cognitive abnormalities in excessive daytime sleepiness (EDS) using cognitive evoked potentials (P300), and to evaluate if P300 measures differentiate among disorders of EDS, a series of EDS subjects were administered a polysomnogram, auditory and visual P300 testing using 31 scalp electrodes, and a multiple sleep latency test. P300 variables were compared with those of normal subjects. Forty normal subjects ages 16 to 65 years, and 69 EDS patients ages 16 to 65 years were used. Of these, 39 had profound obstructive sleep apnea (OSA, Respiratory Disturbance Index or RDI > 80/h sleep) with severe somnolence (Mean Sleep Latency < 5 min). Twenty-two had idiopathic hypersomnia (IH). Eight had narcolepsy. The normals and the three EDS groups did not differ in age. IH and profound OSA patients had longer visual P300 latency than normals or narcolepsy patients (p < 0.05). (p < 0.05). IH and profound OSA patients had longer auditory P300 latency than normals. They had smaller auditory P300 amplitude than narcolepsy patients. There were visual P300 latency topographic differences between normals and profound OSA patients. In conclusion, IH and profound OSA patients show cognitive evoked potential evidence of cognitive dysfunction. Narcolepsy patients do not show such evidence. Visual P300 latency differentiates among disorders of EDS.

Treatment of narcolepsy-cataplexy syndrome with the new selective and reversible MAO-A inhibitor brofaromine-a pilot study

Eighteen narcoleptic patients were treated in a single-blind study with brofaromine, a new selective and reversible MAO-A-inhibitor. After a drug-free period of seven days, brofaromine was administered for two weeks. Patients were treated with 75 mg brofaromine for the first week and with 150 mg brofaromine for the second week of the study. After an adaptation night nocturnal sleep EEGs were recorded under placebo before brofaromine was given, one week later under 75 mg, and another week later under 150 mg brofaromine. Excessive daytime sleepiness (EDS) was evaluated under placebo at the beginning of the study, under 75 mg at the end of the first week, and under 150 mg brofaromine at the end of the second week by means of the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT). The number of cataplexies was protocolled by the patients. Compared to placebo the administration of 150 mg brofaromine led to a significant increase of sleep latency in the MLST as well as in the MWT. REM sleep was significantly suppressed in the nocturnal sleep EEG, in the MSLT and in the MWT. The number of cataplexies protocolled by the patient was significantly decreased under 150 mg of brofaromine compared to placebo. Improvement of vigilance and cataplexy occurred in dose-dependent manner. No serious side effects were observed. The results of the present single-blind study indicate that brofaromine seems to be a well-tolerated and effective drug for the treatment of excessive daytime sleepiness and cataplexy in narcoleptic patients.

Daytime sleepiness after long-term continuous positive airway pressure (CPAP) treatment in obstructive sleep apnea syndrome

A modified maintenance of wakefulness test was performed in 58 patients with obstructive sleep apnea (OSA) syndrome before treatment and after long-term (554 +/- 28 days) home therapy with nasal continuous positive airway pressure (CPAP). Before treatment the patients had a shorter mean sleep latency than controls (16 +/- 1 vs. 27 +/- 1 min, mean +/- SEM, P less than 0.001). After treatment, the mean sleep latency increased to 20 +/- 1 min (P less than 0.002 as compared to baseline), but was still shorter than in controls (P less than 0.001). The incomplete normalization of the mean latency contrasted with the patients' claim that they no longer felt sleepy. The improvement in daytime alertness was significantly correlated with the reduction in sleep fragmentation after CPAP treatment and with the baseline mean sleep latency. These results support the hypothesis that sleep disruption related to respiratory events plays a role in the pathogenesis of daytime sleepiness.

Maintenance of wakefulness test in obstructive sleep apnea syndrome

The usefulness of a 40-min per trial version of the maintenance of wakefulness test was assessed in 322 patients with obstructive sleep apnea. This test is a variant of the multiple sleep latency test in which patients are asked to remain awake in a quiet darkened room, and then monitored for electroencephalographic sleep onset. The four trials of the test are each stopped after 40 min. The mean sleep latency for all patients was 26.0 +/- 11.8 (SD) min. In a group of 24 patients who underwent treatment with nasal continuous positive airway pressure, the mean sleep latency increased from 18.0 +/- 12.3 to 31.9 +/- 10.4. The strongest nocturnal correlates of the MWT sleep latency were respiratory arousal index (r = -.35), mean oxygen saturation (r = .30), and weight/height ratio (r = -.25). These correlations were comparable to other studies using the MSLT. There were strong intercorrelations among the variables. In the more severe groups, measures of hypoxemia were more strongly correlated with MWT sleep latency. A two-factor analysis of variance using respiratory arousal index and several measures of oxyhemoglobin saturation indicated that both arousals from sleep and degree of hypoxemia contribute interactively to daytime dysfunction in patients with sleep apnea. The MWT appears useful in evaluating disability from daytime sleepiness.

Maintenance of wakefulness test and multiple sleep latency test. Measurement of different abilities in patients with sleep disorders

The multiple sleep latency test and the maintenance of wakefulness test were administered on the same day to 258 consecutive patients whose clinical presentation required evaluation for excessive sleepiness. While the MSLT is the standard test for assessing excessive daytime sleepiness, the MWT may have some clinical advantage over the MSLT when the assessment of daytime alertness is the primary goal. To explore further the relationship between alertness and sleepiness, we have conducted a thorough analysis of the similarities, differences, and correlations between MWT and MSLT. The results of this study show that the coefficient of correlation between MSLT and MWT (r = 0.41), although statistically significant, accounts for less than 17 percent of the variability between the two tests. Factor analysis suggests that two factors, alertness and sleepiness, account for 91 percent of all variance. Our data demonstrate that patients with diagnosable disorders of excessive somnolence may be discordant on the two tests (eg, having low sleep latency on MSLT but high sleep latency on MWT). Specifically, we found that some patients with abnormally low MSLT scores were able to stay awake when asked to do so on the MWT, and conversely, some patients who failed to stay awake when asked to do so on the MWT were unable to fall asleep quickly on the MSLT. We conclude that the MWT and MSLT measure different abilities and that the MWT may be a useful adjuvant daytime test in many clinical situations.

Narcolepsy

Narcolepsy is a neurological condition with a prevalence of up to 1 per 1,000 that is characterized by irresistible bouts of sleep. Associated features include the pathological manifestations of rapid-eye-movement (REM) sleep: cataplexy, sleep paralysis, hypnagogic hallucinations, and abnormal sleep-onset REM periods and disturbed nocturnal sleep. The condition is strongly associated with the HLA-DR2 and DQw1 phenotype. The phenomenology of narcolepsy is discussed, and diagnostic procedures are reviewed. Treatment modalities involving central nervous system stimulants for somnolence and tricyclic drugs for REM-sleep abnormalities are discussed. Sleep laboratory studies on the treatment efficacy of methylphenidate, pemoline, dextroamphetamine, protriptyline, and viloxazine are presented. Data suggest that: (1) methylphenidate and dextroamphetamine objectively improve somnolence; (2) pemoline, at doses up to 112.5 mg, is less effective in controlling somnolence but may improve certain aspects of performance; and (3) protriptyline and viloxazine are effective anticataplectic agents that produce little improvement in somnolence.

Auditory event-related potentials and brain dysfunction in sleep apnea

Auditory event-related potentials (ERPs) were recorded from 14 subjects with obstructive sleep apnea (OSA) before and after treatment with nasal continuous positive airway pressure (nCPAP). After 2 nights of treatment, there was dramatic improvement in the sleep patterns of the OSA patients, improvements in measures of apnea severity and oxygenation, and decrease in daytime sleepiness. The results of neuropsychological tests of a broad range of cognitive functions failed to confirm the patients' subjective reports of improvement in psychological functioning after treatment. The latencies of the N2 and P3 components were significantly prolonged prior to treatment, and there was a trend towards smaller N2 and P3 amplitude in the apneic subjects. The latency of P3 (but not N2) changed with treatment, decreasing almost to normative values. The results suggest that ERPs may be useful in documenting neural dysfunction in patients with OSA, in evaluating treatment efficacy, and possibly in determining the causes of the daytime symptoms of OSA.

Compound narcolepsy: sleep pattern and involution

A review of studies of sleep in three-month-old infants, narcoleptics, and normal adults indicates that the sleep pattern in compound narcolepsy is in many ways involuted. Similarities in sleep onsets, REM-specific movement, REM dissociation, ambiguous sleep, nocturnal arousals, diurnal sleep-wake cycles, and relatively limited quiet-awake time are discussed as part of a global inability to inhibit state changes common to both infants and compound narcoleptics. The analogy with infant sleep patterns and results of studies of brain function in narcoleptics suggest that forebrain inhibitory processes are more important in narcoleptic symptomology than is brainstem dysfunction. Puberty and old age are critical periods for the development or exacerbation of the involuted sleep pattern. Closer study of the early development of narcoleptics and of lability of state changes in narcolepsy may aid in diagnosis and prognosis for susceptible individuals.

[Value of the sleep diary in the study of vigilance dis]

This study presents an easy and practical subjective method for evaluating vigilance disorders: the sleep diary. We used it in hypersomnia and deficits of waking. Sleep diaries were filled in by 10 control and 22 hypersomniac subjects. Twenty-four hour polyhypnographic recording allowed the classification of hypersomnia as 13 narcolepsies, 9 hypersomnias with a prevalence of PS, 2 'harmonious' hypersomnias and 1 waking deficit. The sleep diary data (amount of nocturnal sleep and diurnal sleep onset and vigilance decrease) were compared with polygraphic results. According to the diary data, 3 groups of hypersomnia appeared with regard to the time at which sleep onset occurred. The first group presented an increase of sleep onsets at 2 p.m. In the second group, almost exclusively composed of narcoleptic subjects, sleep onsets occurred every 2 h and in the third group they were distributed throughout the day. These results suggest different physiological mechanisms for these 3 groups of hypersomnia. Finally, the sleep diary seems to be an easy and cheap method of evaluating vigilance disorders in hypersomniac subjects during their everyday life.