New 2013 incidence peak in childhood narcolepsy: more than vaccination?

Recent insights into the pathophysiology of narcolepsy type 1

Narcolepsy type 1 (NT1) is a sleep-wake disorder in which people typically experience excessive daytime sleepiness, cataplexy and other sleep-wake disturbances impairing daily life activities. NT1 symptoms are due to hypocretin deficiency. The cause for the observed hypocretin deficiency remains unclear, even though the most likely hypothesis is that this is due to an auto-immune process. The search for autoantibodies and autoreactive T-cells has not yet produced conclusive evidence for or against the auto-immune hypothesis. Other mechanisms, such as reduced corticotrophin-releasing hormone production in the paraventricular nucleus have recently been suggested. There is no reversive treatment, and the therapeutic approach is symptomatic. Early diagnosis and appropriate NT1 treatment is essential, especially in children to prevent impaired cognitive, emotional and social development. Hypocretin receptor agonists have been designed to replace the attenuated hypocretin signalling. Pre-clinical and clinical trials have shown encouraging initial results. A better understanding of NT1 pathophysiology may contribute to faster diagnosis or treatments, which may cure or prevent it.

Infection, vaccination and narcolepsy type 1: Evidence and potential molecular mechanisms

NT1 is a rare, chronic and disabling neurological disease causing excessive daytime sleepiness and cataplexy. NT1 is characterized pathologically by an almost complete loss of neurons producing the hypocretin (HCRT)/orexin neuropeptides in the lateral hypothalamus. While the exact etiology of NT1 is still unknown, numerous studies have provided compelling evidence supporting its autoimmune origin. The prevailing hypothetical view on the pathogenesis of NT1 involves an immune-mediated loss of HCRT neurons that can be triggered by Pandemrix® vaccination and/or by infection in genetically susceptible patients, specifically carriers of the HLA-DQB1*06:02 MHC class II allele. The molecular mechanisms by which infection/vaccination can induce autoimmunity in the case of NT1 remain to be elucidated. In this review, evidence regarding the involvement of vaccination and infection and the potential mechanisms by which it could be linked to the pathogenesis of NT1 will be discussed in light of the existing findings in other autoimmune diseases.

Exploring sleep characteristics in Chinese patients with narcolepsy: insights from the nocturnal sleep onset rapid eye movement period (nSOREMP)

STUDY OBJECTIVES

This study aimed to investigate the unique characteristics and clinical significance of the nocturnal sleep onset rapid eye movement period (nSOREMP) in the Chinese population with narcolepsy, enhancing our understanding and management of the disorder globally.

METHODS

This retrospective analysis investigated narcolepsy in Chinese patients from six hospitals, using the International Classification of Sleep Disorders. A parallel retrospective analysis of the Chinese Clinical Sleep Database focused on polysomnography records was conducted to evaluate nSOREMP prevalence in other sleep disorders.

RESULTS

The study found a 2.51% nSOREMP prevalence in other sleep disorders in the Chinese Clinical Sleep Database. Significant differences in age, N2 and rapid eye movement percentages, rapid eye movement latency, and various indexes were noted among patients with narcolepsy with or without nSOREMP and other sleep disorders with nSOREMP in the Chinese Clinical Sleep Database. nSOREMP prevalence in narcolepsy type 1 was 33.33% and in narcolepsy type 2 was 28.30%. Noteworthy disparities in narcolepsy type 1 included N2 percentages, rapid eye movement latency, and SOREMPs on Multiple Sleep Latency Test. In narcolepsy type 2, differences were significant for age, sleep latency, N2 and rapid eye movement latencies, arousal index, mean sleep latency on the Multiple Sleep Latency Test, and Multiple Sleep Latency Test SOREMPs.

CONCLUSIONS

This study highlights the distinct characteristics of nSOREMP in the Chinese population. Patients exhibiting symptoms suggestive of the onset of narcolepsy are advised to undergo a Multiple Sleep Latency Test, irrespective of the occurrence of SOREMP during nocturnal polysomnography.

CITATION

Zeng S, Feng F, Li W, et al. Exploring sleep characteristics in Chinese patients with narcolepsy: insights from the nocturnal sleep onset rapid eye movement period (nSOREMP). J Clin Sleep Med. 2024;20(8):1349-1355.

Common Childhood Sleep Problems and Disorders

BACKGROUND

Sleep insufficiency and disturbances affect the physical, cognitive, and emotional well-being of children.

OBJECTIVE

To perform a narrative review on common sleep problems and disorders encountered in primary care for children and adolescents.

METHODS

A search of English literature in the Pubmed and Google Scholar databases published from 1 January 2000 till 31 October 2021 was conducted with the keywords "sleep problem" or "sleep disorder" and "child" or "adolescent". Findings in the relevant articles and cross-references were compiled.

RESULTS

Sleep duration and habits of children vary widely across countries with different cultural backgrounds. There is robust evidence to support the promotion of positive bedtime routines and sleep hygiene as prevention and management of sleep problems. 15-70% of parents reported their children having sleep problems or disturbances. Common sleep complaints include difficulty in initiation or maintenance of sleep, abnormal behaviors or movements, snoring or abnormal breathing, and excessive daytime sleepiness. Comprehensive sleep history and a sleep diary are the first steps for evaluation. Home video and actigraphy may be used as preliminary tools to confirm the history. Referrals to a sleep specialist for polysomnography and other tests are needed, if suspecting specific sleep disorders, such as obstructive sleep apnea and narcolepsy, needs timely intervention. Common sleep disorders in different age groups encountered in primary care are reviewed with clinical features, indications for evaluation, and treatment options summarized.

CONCLUSION

Screening for sleep problems shall be an integral part of each child's health care visit. It is important to evaluate the impact of common sleep problems and identify specific sleep disorders for early intervention to prevent long-term adverse outcomes.

The immunopathogenesis of narcolepsy type 1

Narcolepsy type 1 (NT1) is a chronic sleep disorder resulting from the loss of a small population of hypothalamic neurons that produce wake-promoting hypocretin (HCRT; also known as orexin) peptides. An immune-mediated pathology for NT1 has long been suspected given its exceptionally tight association with the MHC class II allele HLA-DQB1*06:02, as well as recent genetic evidence showing associations with polymorphisms of T cell receptor genes and other immune-relevant loci and the increased incidence of NT1 that has been observed after vaccination with the influenza vaccine Pandemrix. The search for both self-antigens and foreign antigens recognized by the pathogenic T cell response in NT1 is ongoing. Increased T cell reactivity against HCRT has been consistently reported in patients with NT1, but data demonstrating a primary role for T cells in neuronal destruction are currently lacking. Animal models are providing clues regarding the roles of autoreactive CD4+ and CD8+ T cells in the disease. Elucidation of the pathogenesis of NT1 will allow for the development of targeted immunotherapies at disease onset and could serve as a model for other immune-mediated neurological diseases.

Narcolepsy and H1N1 influenza immunology a decade later: What have we learned?

In the wake of the A/California/7/2009 H1N1 influenza pandemic vaccination campaigns in 2009-2010, an increased incidence of the chronic sleep-wake disorder narcolepsy was detected in children and adolescents in several European countries. Over the last decade, in-depth epidemiological and immunological studies have been conducted to investigate this association, which have advanced our understanding of the events underpinning the observed risk. Narcolepsy with cataplexy (defined as type-1 narcolepsy, NT1) is characterized by an irreversible and chronic deficiency of hypocretin peptides in the hypothalamus. The multifactorial etiology is thought to include genetic predisposition, head trauma, environmental triggers, and/or infections (including influenza virus infections), and an increased risk was observed following administration of the A/California/7/2009 H1N1 vaccine Pandemrix (GSK). An autoimmune origin of NT1 is broadly assumed. This is based on its strong association with a predisposing allele (the human leucocyte antigen DQB1*0602) carried by the large majority of NT1 patients, and on links with other immune-related genetic markers affecting the risk of NT1. Presently, hypotheses on the underlying potential immunological mechanisms center on molecular mimicry between hypocretin and peptides within the A/California/7/2009 H1N1 virus antigen. This molecular mimicry may instigate a cross-reactive autoimmune response targeting hypocretin-producing neurons. Local CD4⁺ T-cell responses recognizing peptides from hypocretin are thought to play a central role in the response. In this model, cross-reactive DQB1*0602-restricted T cells from the periphery would be activated to cross the blood-brain barrier by rare, and possibly pathogen-instigated, inflammatory processes in the brain. Current hypotheses suggest that activation and expansion of cross-reactive T-cells by H1N1/09 influenza infection could have been amplified following the administration of the adjuvanted vaccine, giving rise to a “two-hit” hypothesis. The collective in silico, in vitro, and preclinical in vivo data from recent and ongoing research have progressively refined the hypothetical model of sequential immunological events, and filled multiple knowledge gaps. Though no definitive conclusions can be drawn, the mechanistical model plausibly explains the increased risk of NT1 observed following the 2009-2010 H1N1 pandemic and subsequent vaccination campaign, as outlined in this review.

Increased incidence of pediatric narcolepsy following the 2009 H1N1 pandemic: a report from the pediatric working group of the sleep research network

This study was aimed to evaluate the yearly incidence of pediatric narcolepsy prior to and following the 2009 H1N1 pandemic and to evaluate seasonal patterns of narcolepsy onset and associations with H1N1 influenza infection in the United States. This was a multicenter retrospective study with prospective follow-up. Participants were recruited from members of the Pediatric Working Group of the Sleep Research Network including 22 sites across the United States. The main outcomes were monthly and yearly incident cases of childhood narcolepsy in the United States, and its relationship to historical H1N1 influenza data. A total of 950 participants were included in the analysis; 487 participants were male (51.3%). The mean age at onset of excessive daytime sleepiness (EDS) was 9.6  ±  3.9 years. Significant trend changes in pediatric narcolepsy incidence based on EDS onset (p  <  .0001) occurred over the 1998–2016 period, peaking in 2010, reflecting a 1.6-fold increase in narcolepsy incidence. In addition, there was significant seasonal variation in narcolepsy incident cases, with increased cases in spring (p  <  .05). Cross-correlation analysis demonstrated a significant correlation between monthly H1N1 infection and monthly narcolepsy incident cases (p  =  .397, p  <  .0001) with a lag time of 8 months. We conclude that there is a significant increase in pediatric narcolepsy incidence after the 2009 H1N1 pandemic in the United States. However, the magnitude of increase is lower than reported in European countries and in China. The temporal correlation between monthly H1N1 infection and monthly narcolepsy incidence, suggests that H1N1 infection may be a contributing factor to the increased pediatric narcolepsy incidence after the 2009 H1N1 pandemics.

Data-Driven Phenotyping of Central Disorders of Hypersomnolence With Unsupervised Clustering

BACKGROUND AND OBJECTIVES

Recent studies fueled doubts as to whether all currently defined central disorders of hypersomnolence are stable entities, especially narcolepsy type 2 and idiopathic hypersomnia. New reliable biomarkers are needed, and the question arises of whether current diagnostic criteria of hypersomnolence disorders should be reassessed. The main aim of this data-driven observational study was to see whether data-driven algorithms would segregate narcolepsy type 1 and identify more reliable subgrouping of individuals without cataplexy with new clinical biomarkers.

METHODS

We used agglomerative hierarchical clustering, an unsupervised machine learning algorithm, to identify distinct hypersomnolence clusters in the large-scale European Narcolepsy Network database. We included 97 variables, covering all aspects of central hypersomnolence disorders such as symptoms, demographics, objective and subjective sleep measures, and laboratory biomarkers. We specifically focused on subgrouping of patients without cataplexy. The number of clusters was chosen to be the minimal number for which patients without cataplexy were put in distinct groups.

RESULTS

We included 1,078 unmedicated adolescents and adults. Seven clusters were identified, of which 4 clusters included predominantly individuals with cataplexy. The 2 most distinct clusters consisted of 158 and 157 patients, were dominated by those without cataplexy, and among other variables, significantly differed in presence of sleep drunkenness, subjective difficulty awakening, and weekend-week sleep length difference. Patients formally diagnosed as having narcolepsy type 2 and idiopathic hypersomnia were evenly mixed in these 2 clusters.

DISCUSSION

Using a data-driven approach in the largest study on central disorders of hypersomnolence to date, our study identified distinct patient subgroups within the central disorders of hypersomnolence population. Our results contest inclusion of sleep-onset REM periods in diagnostic criteria for people without cataplexy and provide promising new variables for reliable diagnostic categories that better resemble different patient phenotypes. Cluster-guided classification will result in a more solid hypersomnolence classification system that is less vulnerable to instability of single features.

Narcolepsy: a model interaction between immune system, nervous system, and sleep-wake regulation

Narcolepsy is a rare chronic neurological disorder characterized by an irresistible excessive daytime sleepiness and cataplexy. The disease is considered to be the result of the selective disruption of neuronal cells in the lateral hypothalamus expressing the neuropeptide hypocretin, which controls the sleep-wake cycle. Diagnosis and management of narcolepsy represent still a substantial medical challenge due to the large heterogeneity in the clinical manifestation of the disease as well as to the lack of understanding of the underlying pathophysiological mechanisms. However, significant advances have been made in the last years, thus opening new perspective in the field. This review describes the current knowledge of clinical presentation and pathology of narcolepsy as well as the existing diagnostic criteria and therapeutic intervention for the disease management. Recent evidence on the potential immune-mediated mechanisms that may underpin the disease establishment and progression are also highlighted.

The month of birth has a seasonal effect in Chinese patients with narcolepsy and cataplexy

STUDY OBJECTIVES

We assessed the yearly seasonal, environmental effects on birth pattern in Chinese patients later diagnosed with narcolepsy and cataplexy and explored if this effect persisted in patients with symptoms onset date before, following, and after the 2009 H1N1 pandemic.

METHODS

A total of 1,942 patients with birth data information and diagnosed narcolepsy with cataplexy were included in this study. The birth month and seasonal effect of 1,064 patients born from 1970 to 2000 were compared to controls (n = 2,028,714) from the general population. Furthermore, birth season effect in 1,373 patients with definite disease onset month were compared among patients with onset date before (n = 595), following (from January 2010 to December 2010) (n = 325), and after (n = 453) the H1N1 pandemic.

RESULTS

Patients with narcolepsy and cataplexy had a significantly different seasonality from the general population (P = .027). The monthly distribution of birth month yielded a peak in November (odds ratio = 1.23 [95% confidence interval, 1.01-1.49], P = .042) and a trough in April (odds ratio = 0.68 [95% confidence interval, 0.52-0.88], P = .004). No significant difference was observed in the birth month across patients with symptom onset dates before, following, and after the 2009 H1N1 pandemic (P = .603).

CONCLUSIONS

This finding across many years of seasonal effect in Chinese narcolepsy cataplexy supports a role for early-life environmental influences on disease development.

CITATION

Guo J, Xu L, Wang J, et al. The month of birth has a seasonal effect in Chinese patients with narcolepsy and cataplexy. J Clin Sleep Med. 2022;18(2):461-467.

Idling for Decades: A European Study on Risk Factors Associated with the Delay Before a Narcolepsy Diagnosis

PURPOSE

Narcolepsy type-1 (NT1) is a rare chronic neurological sleep disorder with excessive daytime sleepiness (EDS) as usual first and cataplexy as pathognomonic symptom. Shortening the NT1 diagnostic delay is the key to reduce disease burden and related low quality of life. Here we investigated the changes of diagnostic delay over the diagnostic years (1990-2018) and the factors associated with the delay in Europe.

PATIENTS AND METHODS

We analyzed 580 NT1 patients (male: 325, female: 255) from 12 European countries using the European Narcolepsy Network database. We combined machine learning and linear mixed-effect regression to identify factors associated with the delay.

RESULTS

The mean age at EDS onset and diagnosis of our patients was 20.9±11.8 (mean ± standard deviation) and 30.5±14.9 years old, respectively. Their mean and median diagnostic delay was 9.7±11.5 and 5.3 (interquartile range: 1.7-13.2 years) years, respectively. We did not find significant differences in the diagnostic delay over years in either the whole dataset or in individual countries, although the delay showed significant differences in various countries. The number of patients with short (≤2-year) and long (≥13-year) diagnostic delay equally increased over decades, suggesting that subgroups of NT1 patients with variable disease progression may co-exist. Younger age at cataplexy onset, longer interval between EDS and cataplexy onsets, lower cataplexy frequency, shorter duration of irresistible daytime sleep, lower daytime REM sleep propensity, and being female are associated with longer diagnostic delay.

CONCLUSION

Our findings contrast the results of previous studies reporting shorter delay over time which is confounded by calendar year, because they characterized the changes in diagnostic delay over the symptom onset year. Our study indicates that new strategies such as increasing media attention/awareness and developing new biomarkers are needed to better detect EDS, cataplexy, and changes of nocturnal sleep in narcolepsy, in order to shorten the diagnostic interval.

"World in motion" - emulsion adjuvants rising to meet the pandemic challenges

Emulsion adjuvants such as MF59 and AS03 have been used for more than two decades as key components of licensed vaccines, with over 100 million doses administered to diverse populations in more than 30 countries. Substantial clinical experience of effectiveness and a well-established safety profile, along with the ease of manufacturing have established emulsion adjuvants as one of the leading platforms for the development of pandemic vaccines. Emulsion adjuvants allow for antigen dose sparing, more rapid immune responses, and enhanced quality and quantity of adaptive immune responses. The mechanisms of enhancement of immune responses are well defined and typically characterized by the creation of an "immunocompetent environment" at the site of injection, followed by the induction of strong and long-lasting germinal center responses in the draining lymph nodes. As a result, emulsion adjuvants induce distinct immunological responses, with a mixed Th1/Th2 T cell response, long-lived plasma cells, an expanded repertoire of memory B cells, and high titers of cross-neutralizing polyfunctional antibodies against viral variants. Because of these various properties, emulsion adjuvants were included in pandemic influenza vaccines deployed during the 2009 H1N1 influenza pandemic, are still included in seasonal influenza vaccines, and are currently at the forefront of the development of vaccines against emerging SARS-CoV-2 pandemic variants. Here, we comprehensively review emulsion adjuvants, discuss their mechanism of action, and highlight their profile as a benchmark for the development of additional vaccine adjuvants and as a valuable tool to allow further investigations of the general principles of human immunity.