Frequency of narcolepsy symptoms and other sleep disorders in narcoleptic patients and their first-degree relatives

Genetics and epigenetics of rare hypersomnia

Herein we focus on connections between genetics and some central disorders of hypersomnolence - narcolepsy types 1 and 2 (NT1, NT2), idiopathic hypersomnia (IH), and Kleine-Levin syndrome (KLS) - for a better understanding of their etiopathogenetic mechanisms and a better diagnostic and therapeutic definition. Gene pleiotropism influences neurological and sleep disorders such as hypersomnia; therefore, genetics allows us to uncover common pathways to different pathologies, with potential new therapeutic perspectives. An important body of evidence has accumulated on NT1 and IH, allowing a better understanding of etiopathogenesis, disease biomarkers, and possible new therapeutic approaches. Further studies are needed in the field of epigenetics, which has a potential role in the modulation of biological specific hypersomnia pathways.

Central disorders of hypersomnolence: diagnostic discrepancies between military and civilian sleep centers

STUDY OBJECTIVES

The majority of active-duty service members obtain insufficient sleep, which can influence diagnostic evaluations for sleep disorders, including disorders of hypersomnolence. An incorrect diagnosis of hypersomnia may be career ending for military service or lead to inappropriate medical care. This study was conducted to assess the rates at which narcolepsy (Nc) and idiopathic hypersomnia (IH) are diagnosed by military vs civilian sleep disorders centers.

METHODS

This retrospective study utilized claims data from the Military Health System Data Repository. The analyses compared diagnostic rates of military personnel by provider type-either civilian provider or military provider-from January 1, 2016 to December 31, 2019. Three diagnostic categories for Nc and IH: Nc or IH, Nc only, and IH only, were assessed with multivariate logistic regression models.

RESULTS

We found that among service members evaluated for a sleep disorder, the odds ratios of a positive diagnosis at a civilian facility vs a military facility for Nc or IH was 2.1, for Nc only was 2.1, and IH only was 2.0 over the 4-year period.

CONCLUSIONS

Civilian sleep specialists were twice as likely to diagnose central disorders of hypersomnolence compared to military specialists. Raising awareness about this discrepancy is critical given the occupational and patient care-related implications of misdiagnoses.

CITATION

Thomas CL, Vattikuti S, Shaha D, et al. Central disorders of hypersomnolence: diagnostic discrepancies between military and civilian sleep centers. J Clin Sleep Med. 2022;18(10):2433-2441.

The development of sleep/wake disruption and cataplexy as hypocretin/orexin neurons degenerate in male vs. female Orexin/tTA; TetO-DTA Mice

Narcolepsy Type 1 (NT1), a sleep disorder with similar prevalence in both sexes, is thought to be due to loss of the hypocretin/orexin (Hcrt) neurons. Several transgenic strains have been created to model this disorder and are increasingly being used for preclinical drug development and basic science studies, yet most studies have solely used male mice. We compared the development of narcoleptic symptomatology in male vs. female orexin-tTA; TetO-DTA mice, a model in which Hcrt neuron degeneration can be initiated by removal of doxycycline (DOX) from the diet. EEG, EMG, subcutaneous temperature, gross motor activity, and video recordings were conducted for 24-h at baseline and 1, 2, 4, and 6 weeks after DOX removal. Female DTA mice exhibited cataplexy, the pathognomonic symptom of NT1, by Week 1 in the DOX(-) condition but cataplexy was not consistently present in males until Week 2. By Week 2, both sexes showed an impaired ability to sustain long wake bouts during the active period, the murine equivalent of excessive daytime sleepiness in NT1. Subcutaneous temperature appeared to be regulated at lower levels in both sexes as the Hcrt neurons degenerated. During degeneration, both sexes also exhibited the "Delta State", characterized by sudden cessation of activity, high delta activity in the EEG, maintenance of muscle tone and posture, and the absence of phasic EMG activity. Since the phenotypes of the two sexes were indistinguishable by Week 6, we conclude that both sexes can be safely combined in future studies to reduce cost and animal use.

Narcolepsy with intermediate cerebrospinal level of hypocretin-1

STUDY OBJECTIVES

To describe the phenotype of narcolepsy with intermediate cerebrospinal hypocretin-1 levels (CSF hcrt-1).

METHODS

From 1600 consecutive patients with narcolepsy from Bologna and Montpellier sleep centers we selected patients with intermediate CSF hcrt-1 levels (110-200 pg/ml). Clinical, neurophysiological and biological data were contrasted for the presence of cataplexy, HLA-DQB1*06:02, and median CSF hcrt-1 levels (149.34 pg/mL).

RESULTS

Forty-five (55% males, aged 35 ± 17 years) patients (2.8% of all cases) were included. Thirty-three (73%) were HLA-DQB1*06:02, 29 (64%) reported cataplexy (21, 72.4% with typical features), and 5 (11%) had presumed secondary etiology. Cataplexy was associated with other core narcolepsy symptoms, increased sleep onset REM periods, and nocturnal sleep disruption. Cataplexy and irrepressible daytime sleep were more frequent in HLA DQB1*06:02 positive patients. Lower CSF hcrt-1 levels were associated with hallucinations.

CONCLUSION

Narcolepsy with intermediate CSF hcrt-1 level is a rare condition with heterogeneous phenotype. HLA DQB1*06:02 and lower CSF hcrt-1 were associated with typical narcolepsy features, calling for future research to distinguish incomplete from secondary narcolepsy forms.

High nocturnal sleep fragmentation is associated with low T lymphocyte P2Y11 protein levels in narcolepsy type 1

STUDY OBJECTIVES

Narcolepsy type 1 (NT1) is associated with hypocretin neuron loss. However, there are still unexplained phenotypic NT1 features. We investigated the associations between clinical and sleep phenotypic characteristics, the NT1-associated P2RY11 polymorphism rs2305795, and P2Y11 protein levels in T lymphocytes in patients with NT1, their first-degree relatives and unrelated controls.

METHODS

The P2RY11 SNP was genotyped in 100 patients (90/100 H1N1-(Pandemrix)-vaccinated), 119 related and 123 non-related controls. CD4 and CD8 T lymphocyte P2Y11 protein levels were quantified using flow cytometry in 167 patients and relatives. Symptoms and sleep recording parameters were also collected.

RESULTS

We found an association between NT1 and the rs2305795 A allele (OR = 2, 95% CI (1.3, 3.0), p = 0.001). T lymphocyte P2Y11 protein levels were significantly lower in patients and relatives homozygous for the rs2305795 risk A allele (CD4: p = 0.012; CD8: p = 0.007). The nocturnal sleep fragmentation index was significantly negatively correlated with patients' P2Y11 protein levels (CD4: p = 0.004; CD8: p = 0.006). Mean MSLT sleep latency, REM-sleep latency, and core clinical symptoms were not associated with P2Y11 protein levels.

CONCLUSIONS

We confirmed that the P2RY11 polymorphism rs2305795 is associated with NT1 also in a mainly H1N1-(Pandemrix)-vaccinated cohort. We demonstrated that homozygosity for the A risk allele is associated with lower P2Y11 protein levels. A high level of nocturnal sleep fragmentation was associated with low P2Y11 levels in patients. This suggests that P2Y11 has a previously unknown function in sleep-wake stabilization that affects the severity of NT1.

Symptom measures in pediatric narcolepsy patients: a review

Purpose

This study aimed to provide a summary of the measures to assess narcoleptic symptoms or complications in pediatric narcolepsy patients.

Methods

We searched in the National Center for Biotechnology Information (NCBI) for measures of narcoleptic symptoms for pediatric patients. Further review was conducted if relevant questionnaires or information were mentioned.

Results

There were only two narcolepsy-specific questionnaires, the narcolepsy severity scale and Ullanlinna Narcolepsy Scale, neither of them was developed or validated in the pediatric population. For cataplexy, all the measures were study-specific diaries and were not validated questionnaires. For excessive daytime sleepiness, the Epworth Sleepiness Scale was most frequently used to measure excessive daytime sleepiness in children. For nighttime sleep, the Children’s Sleep Habits Questionnaire was most frequently used. For depression, the Children Depression Inventory was the most frequently used. For attention-deficit/hyperactivity disorder, the Child Behavior Checklist was the most frequently used. For quality of life, KIDSCREEN was most frequently used.

Conclusions

At present, there is a lack of disease-specific and validated questionnaires for pediatric narcoleptic patients. This need can be met by modifying and adjusting the existing adult questionnaires and developing new questionnaires for pediatric narcoleptic patients.

Single center analysis of patients with H1N1 vaccine-related narcolepsy and sporadic narcolepsy presenting over the same time period

STUDY OBJECTIVES

We aimed to describe the clinical features of narcolepsy in patients referred to our sleep center between 2009 and 2016, and to compare these features across age groups and between sporadic vs AS03-adjuvanted H1N1 influenza vaccine-related patients.

METHODS

This is a retrospective, consecutive study of adult and pediatric narcolepsy patients in the Republic of Ireland. All participants underwent structured assessments, including polysomnography and the Multiple Sleep Latency Test. Brain magnetic resonance imaging, hypocretin levels, and human leukocyte antigen typing were also carried out on the majority of patients. Patients were compared across age groups as well as etiology.

RESULTS

The conditions of 40 (74%) patients were vaccine-related. The median age was 13.5 years and time from symptom onset to diagnosis was 112 weeks. Median time from vaccination to symptom onset was 26 weeks. In children, hypnogogic hallucinations and sleep paralysis were less frequent than in adults (17% vs 67%, P = .018 and 0% vs 75%, P < .0005). Sleep latency determined by the Multiple Sleep Latency Test was shorter in children than adults (median 1.75 vs 4 minutes, P = .011). Patients with vaccine-related and sporadic narcolepsies had typical clinical presentations. Vaccine-related patients had longer polysomnography latency (median 10.5 vs 5 minutes, P = .043), longer stage N2 sleep (209.6 ± 44.6 vs 182.3 ± 34.2 minutes, P = .042), and a trend toward longer total sleep times (P = .09). No differences were noted in relation to Multiple Sleep Latency Test, hypocretin, human leukocyte antigen typing, and magnetic resonance imaging.

CONCLUSIONS

Results show that vaccine-related patients greatly outnumbered sporadic patients during the study period and suggest that sporadic and vaccine-related narcolepsy are clinically similar entities.

Chinese version of narcolepsy severity scale: a validation study

BACKGROUND

The narcolepsy severity scale (NSS) was developed to measure the severity and consequences of symptoms in patients with narcolepsy. The scale has been validated in France, though no other studies have further validated this instrument. The current study aimed to present psychometric properties and describe the score distribution of the Chinese-NSS.

METHODS

One hundred twenty-two patients with narcolepsy (41 females and 81 males; mean age 26.14 ± 15.40 years) participated in the study. All patients completed the Chinese-NSS. Cronbach's α, item-total score correlations, exploratory factor analysis (EFA), and correlations between NSS total scores and clinical or sleep parameters were then calculated.

RESULTS

EFA yielded a three-factor model. Internal consistency was acceptable (Cronbach'sα = 0.799). The NSS total score had significant correlations with the Epworth sleepiness score (0.447), pediatric daytime sleepiness scale (0.318), the insomnia severity index (0.592), Beck depression inventory (0.593), EurQol five dimensions-utility (0.457), EurQol five dimensions -VAS (- 0.323), the sleep disturbance scale for children (0.440), the children depression inventory (0.553), and the pediatric quality of life inventory (0.555) total scores, demonstrating acceptable convergence as predicted.

CONCLUSIONS

The current study is the first validation study of the narcolepsy severity scale in an Asian population. The findings validated the Chinese-narcolepsy severity scale in a Chinese population with acceptable psychometric properties. There are minor differences between our results and those of the original study due to cultural differences.

HLA and sleep parameter associations in post-H1N1 narcolepsy type 1 patients and first-degree relatives

Study Objectives

To explore HLA (human leukocyte antigen) in post-H1N1 narcolepsy type 1 patients (NT1), first-degree relatives and healthy controls, and assess HLA associations with clinical and sleep parameters in patients and first-degree relatives.

Methods

Ninety post-H1N1 NT1 patients and 202 of their first-degree relatives were HLA-genotyped (next generation sequencing) and phenotyped (semistructured interviews, Stanford Sleep Questionnaire, polysomnography, and multiple sleep latency test). HLA allele distributions were compared between DQB1*06:02-heterozygous individuals (77 patients, 59 parents, 1230 controls). A subsample (74 patients, 114 relatives) was investigated for associations between HLA-loci and continuous sleep variables using logistic regression. Identified candidate HLA-loci were explored for HLA allele associations with hypnagogic hallucinations and sleep paralysis in 90 patients, and patient allele findings were checked for similar associations in 202 relatives.

Results

DQB1*06:02 heterozygous post-H1N1 NT1 patients (84.4% H1N1-vaccinated) showed several significant HLA associations similar to those reported previously in samples of mainly sporadic NT1, i.e. DQB1*03:01, DRB1*04:01, DRB1*04:02, DRB1*04:07, DRB1*11:04, A*25:01, B*35:03, and B*51:01, and novel associations, i.e. B*14:02, C*01:02, and C*07:01. Parents HLA alleles did not deviate significantly from controls. The HLA-C locus was associated with sleep parameters in patients and relatives. In patients C*02:02 seems to be associated with protective effects against sleep paralysis and hypnagogic hallucinations.

Conclusions

Our findings of similar risk/protective HLA-alleles in post-H1N1 as in previous studies of mainly sporadic narcolepsy support similar disease mechanisms. We also report novel allelic associations. Associations between HLA-C and sleep parameters were seen independent of NT1 diagnosis, supporting involvement of HLA-C in sleep subphenotypes.

Hypocretin-deficient narcolepsy patients have abnormal brain activation during humor processing

Study Objectives

To assess brain activation patterns in response to fun-rated and neutral-rated movies we performed functional magnetic resonance imaging (fMRI) during a humor-paradigm in narcolepsy type 1 (NT1) patients with cataplexy (muscle atonia triggered by emotions) and controls.

Methods

The fMRI-humor-paradigm consisted of short movies (25/30 with a humorous punchline; 5/30 without a humorous punchline [but with similar build-up/anticipation]) rated by participants based on their humor experience. We included 41 NT1 patients and 44 controls. Group-level inferences were made using permutation testing.

Results

Permutation testing revealed no group differences in average movie ratings. fMRI analysis found no group differences in brain activations to fun-rated movies. Patients showed significantly higher activations compared to controls during neutral-rated movies; including bilaterally in the thalamus, pallidum, putamen, amygdala, hippocampus, middle temporal gyrus, cerebellum, brainstem and in the left precuneus, supramarginal gyrus, and caudate. We found no brain overactivation for patients during movies without a humorous punchline (89.0% neutral-rated). Group analyses revealed significantly stronger differentiation between fun-rated and neutral-rated movies in controls compared with patients (patients showed no significant differentiation), including bilaterally in the inferior frontal gyrus, thalamus, putamen, precentral gyrus, lingual gyrus, supramarginal gyrus, occipital areas, temporal areas, cerebellum and in the right hippocampus, postcentral gyrus, pallidum, and insula.

Conclusion

Patients showed significantly higher activations in several cortical and subcortical regions during neutral-rated movies, with no differentiation from activations during fun-rated movies. This lower threshold for activating the humor response (even during neutral-rated movies), might represent insight into the mechanisms associated with cataplexy.

Transcranial Direct Current Stimulation Does Not Counteract Cognitive Fatigue, but Induces Sleepiness and an Inter-Hemispheric Shift in Brain Oxygenation

Sustained cognitive demands may result in cognitive fatigue (CF), eventually leading to decreased behavioral performance and compromised brain resources. In the present study, we tested the hypothesis that transcranial direct current stimulation (tDCS) would counteract the behavioral and neurophysiological effects of CF. Twenty young healthy participants were tested in a within-subject counterbalanced order across two different days. Anodal tDCS (real vs. sham) was applied over the left prefrontal cortex. In the real tDCS condition, a current of 1.5 mA was delivered for 25 min. Cortical oxygenation changes were measured using functional Near Infrared Spectroscopy (fNIRS) on the frontal cortices. CF was triggered using the TloadDback task, a sustained working memory paradigm that allows tailoring task demands according to each individual's maximal cognitive capacity. Sustained cognitive load-related effects were assessed using pre- versus post-task subjective fatigue and sleepiness scales, evolution of performance accuracy within the task, indirect markers of dopaminergic activity (eye blinks), and cortical oxygenation changes (fNIRS) both during the task and pre- and post-task resting state periods. Results consistently disclosed significant CF-related effects on performance. Transcranial DCS was not effective to counteract the behavioral effects of CF. In the control (sham tDCS) condition, cerebral oxygen exchange (COE) levels significantly increased in the right hemisphere during the resting state immediately after the induction of CF, suggesting a depletion of brain resources. In contrast, tDCS combined with CF induction significantly shifted interhemispheric oxygenation balance during the post-training resting state. Additionally, increased self-reported sleepiness was associated with brain activity in the stimulated hemisphere after recovery from CF during the tDCS condition only, which might reflect a negative middle-term effect of tDCS application.

Clinical Characteristics and Burden of Illness in Pediatric Patients with Narcolepsy

BACKGROUND

Narcolepsy is a chronic and lifelong neurologic disorder with onset commonly occurring in childhood or adolescence, and affecting approximately 0.025% to 0.05% of the general population. The primary symptom is excessive daytime sleepiness, which is accompanied by cataplexy in 70% of patients. Other common symptoms include sleep paralysis, hallucinations upon falling asleep or waking, and disrupted nocturnal sleep. Narcolepsy is associated with a considerable burden of illness (BOI), which has been well characterized in adults, and is exacerbated by delays in symptom recognition, diagnosis, and intervention.

METHODS

This review describes the specific characteristics and BOI of pediatric narcolepsy, using a wide range of published research data.

RESULTS

Pediatric narcolepsy presents distinct challenges in diagnosis and management. Narcolepsy symptoms often initially manifest differently in children and adolescents versus adults, which may pose diagnostic dilemmas. Children often respond to sleepiness with irritability, hyperactivity, and poor attention, which may be misinterpreted as misbehavior or neurocognitive sequelae of other conditions. Pediatric cataplexy symptoms may include subtle and unusual facial expressions or choreic-like movements, which are not observed in adults. Insufficient sleep and circadian rhythm disorders presenting with excessive daytime sleepiness are common in adolescents, potentially confounding narcolepsy diagnosis. Pediatric narcolepsy is also associated with comorbidities including rapid weight gain, precocious puberty, and attention deficit hyperactivity disorder, and increased risk for deficits in social functioning, depression, and anxiety. School performance is also typically impaired, requiring special education services.

CONCLUSIONS

Thus, the discrete BOI of pediatric narcolepsy underscores the need for prompt and accurate diagnosis, and appropriate treatment of this disorder.

The spectrum of REM sleep-related episodes in children with type 1 narcolepsy

Type 1 narcolepsy is a central hypersomnia due to the loss of hypocretin-producing neurons and characterized by cataplexy, excessive daytime sleepiness, sleep paralysis, hypnagogic hallucinations and disturbed nocturnal sleep. In children, close to the disease onset, type 1 narcolepsy has peculiar clinical features with severe cataplexy and a complex admixture of movement disorders occurring while awake. Motor dyscontrol during sleep has never been systematically investigated. Suspecting that abnormal motor control might affect also sleep, we systematically analysed motor events recorded by means of video polysomnography in 40 children with type 1 narcolepsy (20 females; mean age 11.8 ± 2.6 years) and compared these data with those recorded in 22 age- and sex-matched healthy controls. Motor events were classified as elementary movements, if brief and non-purposeful and complex behaviours, if simulating purposeful behaviours. Complex behaviours occurring during REM sleep were further classified as 'classically-defined' and 'pantomime-like' REM sleep behaviour disorder episodes, based on their duration and on their pattern (i.e. brief and vivid-energetic in the first case, longer and with subcontinuous gesturing mimicking daily life activity in the second case). Elementary movements emerging either from non-REM or REM sleep were present in both groups, even if those emerging from REM sleep were more numerous in the group of patients. Conversely, complex behaviours could be detected only in children with type 1 narcolepsy and were observed in 13 patients, with six having 'classically-defined' REM sleep behaviour disorder episodes and seven having 'pantomime-like' REM sleep behaviour disorder episodes. Complex behaviours during REM sleep tended to recur in a stereotyped fashion for several times during the night, up to be almost continuous. Patients displaying a more severe motor dyscontrol during REM sleep had also more severe motor disorder during daytime (i.e. status cataplecticus) and more complaints of disrupted nocturnal sleep and of excessive daytime sleepiness. The neurophysiological hallmark of this severe motor dyscontrol during REM sleep was a decreased atonia index. The present study reports for the first time the occurrence of a severe and peculiar motor disorder during REM sleep in paediatric type 1 narcolepsy and confirms the presence of a severe motor dyscontrol in these patients, emerging not only from wakefulness (i.e. status cataplecticus), but also from sleep (i.e. complex behaviours during REM sleep). This is probably related to the acute imbalance of the hypocretinergic system, which physiologically acts by promoting movements during wakefulness and suppressing them during sleep.

Patient-Reported Measures of Narcolepsy: The Need for Better Assessment

STUDY OBJECTIVES

Narcolepsy, a chronic disorder of the central nervous system, is clinically characterized by a symptom pentad that includes excessive daytime sleepiness, cataplexy, sleep paralysis, hypnopompic/hypnagogic hallucinations, and disrupted nighttime sleep. Ideally, screening and diagnosis instruments that assist physicians in evaluating a patient for type 1 or type 2 narcolepsy would be brief, easy for patients to understand and physicians to score, and would identify or rule out the need for electrophysiological testing.

METHODS

A search of the literature was conducted to review patient-reported measures used for the assessment of narcolepsy, mainly in clinical trials, with the goal of summarizing existing scales and identifying areas that may require additional screening questions and clinical practice scales.

RESULTS

Of the seven scales reviewed, the Epworth Sleepiness Scale continues to be an important outcome measure to screen adults for excessive daytime sleepiness, which may be associated with narcolepsy. Several narcolepsy-specific scales have demonstrated utility, such as the Ullanlinna Narcolepsy Scale, Swiss Narcolepsy Scale, and Narcolepsy Symptom Assessment Questionnaire, but further validation is required.

CONCLUSIONS

Although the narcolepsy-specific scales currently in use may identify type 1 narcolepsy, there are no validated questionnaires to identify type 2 narcolepsy. Thus, there remains a need for short, easily understood, and well-validated instruments that can be readily used in clinical practice to distinguish narcolepsy subtypes, as well as other hypersomnias, and for assessing symptoms of these conditions during treatment.

Narcolepsy

Narcolepsy is a chronic sleep disorder that has a typical onset in adolescence and is characterized by excessive daytime sleepiness, which can have severe consequences for the patient. Problems faced by patients with narcolepsy include social stigma associated with this disease, difficulties in obtaining an education and keeping a job, a reduced quality of life and socioeconomic consequences. Two subtypes of narcolepsy have been described (narcolepsy type 1 and narcolepsy type 2), both of which have similar clinical profiles, except for the presence of cataplexy, which occurs only in patients with narcolepsy type 1. The pathogenesis of narcolepsy type 1 is hypothesized to be the autoimmune destruction of the hypocretin-producing neurons in the hypothalamus; this hypothesis is supported by immune-related genetic and environmental factors associated with the disease. However, direct evidence in support of the autoimmune hypothesis is currently unavailable. Diagnosis of narcolepsy encompasses clinical, electrophysiological and biological evaluations, but simpler and faster procedures are needed. Several medications are available for the symptomatic treatment of narcolepsy, all of which have quite good efficacy and safety profiles. However, to date, no treatment hinders or slows disease development. Improved diagnostic tools and increased understanding of the pathogenesis of narcolepsy type 1 are needed and might lead to therapeutic or even preventative interventions.

A practical approach to the diagnosis and management of sleep disorders in patients with multiple sclerosis

Patients with multiple sclerosis (MS) are at increased risk for comorbid sleep disturbances, which can profoundly contribute to poor functional status and fatigue. Insomnia, sleep-disordered breathing, and restless legs syndrome are among the most common sleep disorders experienced by patients with MS. Despite their impact, these underlying sleep disorders may escape routine clinical evaluations in persons with MS, thereby leading to missed opportunities to optimize functional status and quality of life in patients with MS. A practical, systematic approach to the evaluation and treatment of sleep disorders in MS, in the context of MS-specific variables that may influence risk for these conditions or response to therapy, is recommended to facilitate early diagnosis and successful treatment. This review summarizes the most common sleep disorders experienced by persons with MS, and offers a practical approach to diagnosis and management of these conditions.

Operational definitions and algorithms for excessive sleepiness in the general population: implications for DSM-5 nosology

CONTEXT

Excessive sleepiness (ES) is poorly defined in epidemiologic studies, although its adverse implications for safety, health, and optimal social and vocational functioning have been extensively reported.

OBJECTIVE

To determine the importance of ES definition, measurement, and prevalence in the general population, together with its coexisting conditions.

DESIGN

Cross-sectional telephone study.

PARTICIPANTS

A total of 15 929 individuals representative of the adult general population of 15 states in the United States.

MAIN OUTCOME MEASURES

Interviews were carried out using Sleep-EVAL, a knowledge-based expert system for use in epidemiologic studies, focusing on sleep, as well as physical and mental disorders, according to classification in DSM-IV and the second edition of the International Classification of Sleep Disorders. The interviews elicited information on ES, naps, frequency, duration, impairment, and distress associated with ES symptoms.

RESULTS

Excessive sleepiness was reported by 27.8% (95% CI, 27.1%-28.5%) of the sample. Excessive sleepiness with associated symptoms was found in 15.6% of the participants (95% CI, 15.0%-16.2%). Adding an ES frequency of at least 3 times per week for at least 3 months despite normal sleep duration dropped the prevalence to 4.7% of the sample (95% CI, 4.4%-5.0%). The proportion of individuals having social or professional impairment and psychological distress increased with the frequency of ES symptoms during the week and within the same day. In multivariate models, the number of ES episodes per day and severity of ES were identified as the best predictors for impairment/distress. Prevalence of hypersomnia disorder was 1.5% of the participants (95% CI, 1.3%-1.7%). The most common coexisting conditions were mood and substance use disorders.

CONCLUSIONS

Excessive sleepiness is an important problem in the US population, even when using restrictive criteria to define it. Hypersomnia disorder is more prevalent than previously estimated. Excessive sleepiness has to be recognized and given attention by public health authorities, scientists, and clinicians.

Complex movement disorders at disease onset in childhood narcolepsy with cataplexy

Narcolepsy with cataplexy is characterized by daytime sleepiness, cataplexy (sudden loss of bilateral muscle tone triggered by emotions), sleep paralysis, hypnagogic hallucinations and disturbed nocturnal sleep. Narcolepsy with cataplexy is most often associated with human leucocyte antigen-DQB1*0602 and is caused by the loss of hypocretin-producing neurons in the hypothalamus of likely autoimmune aetiology. Noting that children with narcolepsy often display complex abnormal motor behaviours close to disease onset that do not meet the classical definition of cataplexy, we systematically analysed motor features in 39 children with narcolepsy with cataplexy in comparison with 25 age- and sex-matched healthy controls. We found that patients with narcolepsy with cataplexy displayed a complex array of ‘negative’ (hypotonia) and ‘active’ (ranging from perioral movements to dyskinetic–dystonic movements or stereotypies) motor disturbances. ‘Active’ and ‘negative’ motor scores correlated positively with the presence of hypotonic features at neurological examination and negatively with disease duration, whereas ‘negative’ motor scores also correlated negatively with age at disease onset. These observations suggest that paediatric narcolepsy with cataplexy often co-occurs with a complex movement disorder at disease onset, a phenomenon that may vanish later in the course of the disease. Further studies are warranted to assess clinical course and whether the associated movement disorder is also caused by hypocretin deficiency or by additional neurochemical abnormalities.

Pediatric narcolepsy

Narcolepsy is a disabling disease with a prevalence of 0.05%. It is characterized by excessive daytime sleepiness, cataplexy, sleep paralysis, hypnogogic hallucinations, automatic behavior, and disrupted nocturnal sleep. The presentation can be very variable, making diagnosis difficult. Loss of hypocretin containing neurons in the lateral hypothalamus has been noted in autopsy studies, and the cerebrospinal fluid level of hypocretin is reduced in patients with narcolepsy with cataplexy. New treatment options are available for the many symptoms of this disease. Early recognition and treatment can greatly improve the quality of life of patients with narcolepsy. A detail review of the epidemiology, pathophysiology, and management of narcolepsy in children is presented.

Association of narcolepsy-cataplexy with HLA-DRB1 and DQB1 in Mexican patients: a relationship between HLA and gender is suggested

Background

Narcolepsy-cataplexy is characterized by excessive daytime sleepiness with recurrent episodes of irresistible sleep, cataplexy, hallucinations and sleep paralysis. Its aetiology is unknown, but it is positively associated with the human leukocyte antigens (HLA) in all studied populations. The purpose of the present study was to investigate the association of HLA class II DRB1/DQB1 alleles with narcolepsy-cataplexy in Mexican Mestizo patients.

Methods

This is a case-control study of consecutive patients and ethnically matched controls. We included 32 patients diagnosed with typical narcolepsy-cataplexy, of the National Institute of Neurology, of the Institute of Psychiatry and at the Center of Narcolepsy at Stanford University. As healthy controls, 203 Mexican Mestizos were included. DRB1 alleles were identified using sequence based typing. A PCR-SSOP reverse dot blot was used for DQB1 typing. Allele frequency was calculated by direct counting and the significance of the differences was assessed using the Yates Chi square. Odds ratio and confidence intervals were evaluated.

Results

HLA-DRB1*1501 (OR = 8.2; pc < 0.0001) and DQB1*0602 (OR = 8.4; pc < 0.0001) were found positively associated with narcolepsy. When deleting DQB1*0602+ patients from the analysis, DQB1*0301 was also found increased (OR = 2.7; p = 0.035; pc = NS). DQB1*0602/DQB1*0301 genotype was present in 15.6% of the cases (OR = 11.5; p = 0.00035), conferring a high risk. DRB1*0407 (OR = 0.2; p = 0.016 pc = NS) and DQB1*0302(OR = 0.4; p = 0.017, pc = NS) were found decreased in the patients. The gender stratification analysis showed a higher risk in females carrying DRB1*1501 (OR = 15.8, pc < 0.0001) and DQB1*0602 (OR = 19.8, pc < 0.0001) than in males (OR = 5.0 for both alleles; p = 0.012, pc = NS for DRB1 & p = 0.0012, pc = 0.017 for DQB1). The susceptibility alleles found in Mexicans with narcolepsy are also present in Japanese and Caucasians; DRB1*04 linked protection has also been shown in Koreans. A stronger HLA association is suggested in females, in accordance with the sexual dimorphism claimed previously.

Conclusion

This knowledge may contribute to a better understanding of the disease pathogenesis in different populations. The evaluation of the risk to develop narcolepsy-cataplexy in carriers of the described alleles/genotypes may also be possible. A larger sample should be analysed in Mexican and in other Hispanic patients to confirm these results.

From wakefulness to excessive sleepiness: what we know and still need to know

The epidemiological study of hypersomnia symptoms is still in its infancy; most epidemiological surveys on this topic were published in the last decade. More than two dozen representative community studies can be found. These studies assessed two aspects of hypersomnia: excessive quantity of sleep and sleep propensity during wakefulness excessive daytime sleepiness. The prevalence of excessive quantity of sleep when referring to the subjective evaluation of sleep duration is around 4% of the population. Excessive daytime sleepiness has been mostly investigated in terms of frequency or severity; duration of the symptom has rarely been investigated. Excessive daytime sleepiness occurring at least 3 days per week has been reported in between 4% and 20.6% of the population, while severe excessive daytime sleepiness was reported at 5%. In most studies, men and women are equally affected. In the International Classification of Sleep Disorders, hypersomnia symptoms are the essential feature of three disorders: insufficient sleep syndrome, hypersomnia (idiopathic, recurrent or posttraumatic) and narcolepsy. Insufficient sleep syndrome and hypersomnia diagnoses are poorly documented. The co-occurrence of insufficient sleep and excessive daytime sleepiness has been explored in some studies and prevalence has been found in around 8% of the general population. However, these subjects often have other conditions such as insomnia, depression or sleep apnea. Therefore, the prevalence of insufficient sleep syndrome is more likely to be between 1% and 4% of the population. Idiopathic hypersomnia would be rare in the general population with prevalence, around 0.3%. Narcolepsy has been more extensively studied, with a prevalence around 0.045% in the general population. Genetic epidemiological studies of narcolepsy have shown that between 1.5% and 20.8% of narcoleptic individuals have at least one family member with the disease. The large variation is mostly due to the method used to collect the information on the family members; systematic investigation of all family members provided higher results. There is still a lot to be done in the epidemiological field of hypersomnia. Inconsistencies in its definition and measurement limit the generalization of the results. The use of a single question fails to capture the complexity of the symptom. The natural evolution of hypersomnia remains to be documented.

The sleepy adolescent: causes and consequences of sleepiness in teens

The majority of adolescents do not obtain the recommended amount of sleep, resulting in significant daytime sleepiness. For most adolescents, insufficient sleep results from the interaction between intrinsic factors such as puberty and extrinsic factors such as school start times. Insufficient sleep and sleepiness impact all areas of adolescent functioning, including academic, psychological and behavioural, which underscores the importance of evaluating sleepy adolescents. While polysomnography is required for the diagnosis of certain sleep disorders, causes of sleepiness are generally best identified with a detailed sleep history and daily sleep diary. The management of sleep problems in adolescents involves treating any underlying sleep disorders, increasing total sleep time and improving other environmental factors that impact sleep. Recognition and management of insufficient sleep and sleepiness is important for the health and functioning of adolescents.

CSF hypocretin-1 levels and clinical profiles in narcolepsy and idiopathic CNS hypersomnia in Norway

OBJECTIVE

To evaluate the relationship between CSF hypocretin-1 levels and clinical profiles in narcolepsy and CNS hypersomnia in Norwegian patients.

METHOD

CSF hypocretin-1 was measured by a sensitive radioimmunoassay in 47 patients with narcolepsy with cataplexy, 7 with narcolepsy without cataplexy, 10 with idiopathic CNS hypersomnia, and a control group.

RESULTS

Low hypocretin-1 values were found in 72% of the HLA DQB1*0602 positive patients with narcolepsy and cataplexy. Patients with low CSF hypocretin-1 levels reported more extensive muscular involvement during cataplectic attacks than patients with normal levels. Hypnagogic hallucinations and sleep paralysis occurred more frequently in patients with cataplexy than in the other patient groups, but with no correlation to hypocretin-1 levels.

CONCLUSION

About three quarters of the HLA DQB1*0602 positive patients with narcolepsy and cataplexy had low CSF hypocretin-1 values, and appear to form a distinct clinical entity. Narcolepsy without cataplexy could not be distinguished from idiopathic CNS hypersomnia by clinical symptoms or biochemical findings.

The familial risk and HLA susceptibility among narcolepsy patients in Hong Kong Chinese

STUDY OBJECTIVES

To explore the familial aggregation and HLA susceptibility of narcolepsy in Hong Kong Chinese by objective sleep measurements and HLA typing.

DESIGN

Case control design

PARTICIPANTS

Twelve narcoleptic probands, 34 first-degree relatives, and 30 healthy controls.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Each subject underwent a standardized nocturnal polysomnogram (PSG), followed by a daytime multiple sleep latency test (MSLT). HLA typing was performed for all subjects. One relative (2.9%) was diagnosed as suffering from narcolepsy with cataplexy. Nearly 30% of the relatives fulfilled the criteria of narcolepsy spectrum disorder (shortened mean sleep latency [MSL] and/or the presence of sleep onset REM periods [SOREMPs]). When using the population data for comparison, the relative risk of narcolepsy in first-degree relatives was 85.3. The odds ratio of narcolepsy spectrum disorder in first-degree relatives was 5.8 (95% CI: 1.2 - 29.3) when compared to healthy controls. There existed 6 multiplex families, in which all 10 relatives with narcolepsy spectrum disorders, including all 3 relatives with multiple SOREMPs, were positive for HLA DQB1*0602.

CONCLUSIONS

Our study demonstrated a definitive familial aggregation of narcolepsy, narcolepsy spectrum disorders, and possibly cataplexy in Hong Kong Chinese. This familial aggregation supported an inherited basis for narcolepsy spectrum. The tight co-segregation of HLA DQB1*0602 and narcolepsy spectrum disorders might suggest that HLA typing, especially DQB1*0602, at least partly confer the familial risk of narcolepsy. In addition, our study suggested that the subjective questionnaire measurements including Ullanlinna Narcolepsy Scale and Epworth Sleepiness Scale were unable to detect the presence of narcolepsy spectrum disorders among the relatives. A stringent objective measurement-based design for family studies is suggested for future study. Further studies are indicated for the determination of the mode and molecular level of narcolepsy transmission.

Sodium oxybate: neurobiology and clinical efficacy

Sodium oxybate is the sodium salt of γ-hydroxybutyrate (GHB), an endogenous short-chain fatty acid that is speculated to function as a neurotransmitter in the mammalian CNS. Pharmacodynamic effects of exogenously-administered sodium oxybate may include modulating the release of neurotransmitters, including γ-aminobutyric acid, dopamine, endogenous opioids and serotonin, and stimulating release of growth hormone. It is rapidly absorbed, with approximately 25% bioavailability and a plasma half-life of 40–60 min, necessitating twice-nightly dosing. Sodium oxybate is indicated for the treatment of cataplexy and excessive daytime sleepiness in patients with narcolepsy, and has been shown to improve disrupted night-time sleep and increase Stage 3 and 4 (slow-wave restorative) sleep in this patient population. The most common adverse events reported in clinical trials in patients with narcolepsy include headache, nausea, dizziness, nasopharyngitis, somnolence, vomiting and urinary incontinence.

A Review of Pediatric Nonrespiratory Sleep Disorders

Sleep problems are extremely common during childhood, from infancy to adolescence. Despite the prevalence of sleep problems, childhood sleep disorders are often underrecognized and undiagnosed, despite being either preventable or treatable. Sleep impacts almost all aspects of a child's functioning, and thus the increased recognition and treatment of sleep disorders will positively affect a child's well-being. Children experience the same broad range of sleep disturbances encountered in adults, including sleep apnea, insomnia, parasomnia, delayed sleep phase, narcolepsy, and restless legs, but their clinical presentation, evaluation, and management may differ. Although snoring and sleep apnea may be the most common indication for an overnight sleep study in a child, one quarter of children presenting to a sleep clinic for evaluation will have a second sleep diagnosis, which is often nonrespiratory in nature. Especially in children, ruling out sleep apnea is rarely the end point of the sleep evaluation. Clinicians involved in sleep medicine must be prepared to recognize, evaluate, and manage plans for sleep disorders across the lifespan of the patient. This article will provide an updated review of nonrespiratory pediatric sleep disorders within a developmental framework.