Morbidity of childhood onset narcolepsy: a controlled national study

Narcolepsy and rapid eye movement sleep

Since the first description of narcolepsy at the end of the 19th Century, great progress has been made. The disease is nowadays distinguished as narcolepsy type 1 and type 2. In the 1960s, the discovery of rapid eye movement sleep at sleep onset led to improved understanding of core sleep-related disease symptoms of the disease (excessive daytime sleepiness with early occurrence of rapid eye movement sleep, sleep-related hallucinations, sleep paralysis, rapid eye movement parasomnia), as possible dysregulation of rapid eye movement sleep, and cataplexy resembling an intrusion of rapid eye movement atonia during wake. The relevance of non-sleep-related symptoms, such as obesity, precocious puberty, psychiatric and cardiovascular morbidities, has subsequently been recognized. The diagnostic tools have been improved, but sleep-onset rapid eye movement periods on polysomnography and Multiple Sleep Latency Test remain key criteria. The pathogenic mechanisms of narcolepsy type 1 have been partly elucidated after the discovery of strong HLA class II association and orexin/hypocretin deficiency, a neurotransmitter that is involved in altered rapid eye movement sleep regulation. Conversely, the causes of narcolepsy type 2, where cataplexy and orexin deficiency are absent, remain unknown. Symptomatic medications to treat patients with narcolepsy have been developed, and management has been codified with guidelines, until the recent promising orexin-receptor agonists. The present review retraces the steps of the research on narcolepsy that linked the features of the disease with rapid eye movement sleep abnormality, and those that do not appear associated with rapid eye movement sleep.

Narcolepsy and risk of traumatic injury: a population-based matched cohort study

STUDY OBJECTIVES

We evaluated the risk of traumatic injury in patients with narcolepsy compared to the general population.

METHODS

We conducted a population-based matched cohort study using a Japanese health insurance claims database. For each patient with narcolepsy, up to 5 individuals from the general population without narcolepsy were matched by variables such as sex, age, and cohort entry month. The primary outcome was traumatic injury, and the secondary outcome was fracture. The study population was followed for up to 5 years from the cohort entry date. We estimated crude incidence rates, adjusted incidence rate differences, adjusted hazard ratios, and their 95% confidence intervals (CIs) for study outcomes using crude and multivariable Poisson and Cox regression models.

RESULTS

We included 2,451 patients with narcolepsy (mean age, 30.3 years; male, 58.0%) and 10,591 matched individuals (mean age, 30.6 years; male, 58.4%). Crude incidence rate of traumatic injury was 11.4 per 100 person-years for patients with narcolepsy compared with 6.2 per 100 person-years for matched individuals (adjusted incidence rate difference, 6.2 excess events per 100 person-years [95% CI, 4.9-7.4]; adjusted hazard ratio, 1.8 [95% CI, 1.5-2.2]). Crude incidence rate of fracture was 2.3 per 100 person-years for patients with narcolepsy compared with 1.3 per 100 person-years for matched individuals (adjusted incidence rate difference, 1.2 excess events per 100 person-years [95% CI, 0.7-1.7]; adjusted hazard ratio, 1.7 [95% CI, 1.4-2.1]).

CONCLUSIONS

Narcolepsy was associated with increased risk of traumatic injury. For patients with narcolepsy, optimized approaches to injury prevention should be considered.

CITATION

Zheng Y, Fukasawa T, Masuda S, Takeuchi M, Kawakami K. Narcolepsy and risk of traumatic injury: a population-based matched cohort study. J Clin Sleep Med. 2024;20(10):1657-1662.

Sleep disturbance and gastrointestinal cancer risk: a literature review

Sleep, accounting for roughly one-third of a person's life, plays an important role in human health. Despite the close association between sleep patterns and medical diseases proven by several studies, it has been neglected in recent years. Presently, all societies are facing the most challenging health-threatening disease, cancer. Among all cancer types, gastrointestinal (GI) cancers, especially colorectal type, seem to be one of the most relevant to an individual's lifestyle; thus, they can be prevented by modifying behaviors most of the time. Previous studies have shown that disruption of the 24-h sleep-wake cycle increases the chance of colorectal cancer, which can be due to exposure to artificial light at night and some complex genetic and hormone-mediated mechanisms. There has also been some evidence showing the possible associations between other aspects of sleep such as sleep duration or some sleep disorders and GI cancer risk. This review brings some information together and presents a detailed discussion of the possible role of sleep patterns in GI malignancy initiation.

Narcolepsy: Comorbidities, complexities and future directions

Patients with narcolepsy live with a lifelong sleep-wake disorder, impairing their quality of life, productivity, educational and employment outcomes. Clinicians are becoming aware that a significant aspect of the burden of this disease relates to frequent comorbid conditions, including aspects of the patient's emotional, metabolic, sleep and immune health. This review explores the literature describing the comorbidities seen in patients with narcolepsy, to enhance understanding of these often complex presentations. It hopes to encourage a multidisciplinary approach, to collaborate with patients and a broad clinical team, and to maximise clinical and quality of life outcomes, for those living with narcolepsy.

Focus on the Complex Interconnection between Cancer, Narcolepsy and Other Neurodegenerative Diseases: A Possible Case of Orexin-Dependent Inverse Comorbidity

Simple Summary

This narrative review first describes from several points of view the complex interrelationship between cancer and neurodegeneration, with special attention to the mechanisms that might underlie an inverse relationship between them. In particular, the mechanisms that might induce an imbalance between cell apoptotic and proliferative stimuli are discussed. Second, the review summarizes findings on orexins and their involvement in narcolepsy, neurodegenerative diseases, and cancer, starting from epidemiological data then addressing laboratory findings, animal models, and human clinical observational and interventional investigations. Important research efforts are warranted on these topics, as they might lead to novel therapeutic approaches to both neurodegenerative diseases and cancer.

Abstract

Conditions such as Alzheimer’s (AD) and Parkinson’s diseases (PD) are less prevalent in cancer survivors and, overall, cancer is less prevalent in subjects with these neurodegenerative disorders. This seems to suggest that a propensity towards one type of disease may decrease the risk of the other. In addition to epidemiologic data, there is also evidence of a complex biological interconnection, with genes, proteins, and pathways often showing opposite dysregulation in cancer and neurodegenerative diseases. In this narrative review, we focus on the possible role played by orexin signaling, which is altered in patients with narcolepsy type 1 and in those with AD and PD, and which has been linked to β-amyloid brain levels and inflammation in mouse models and to cancer in cell lines. Taken together, these lines of evidence depict a possible case of inverse comorbidity between cancer and neurodegenerative disorders, with a role played by orexins. These considerations suggest a therapeutic potential of orexin modulation in diverse pathologies such as narcolepsy, neurodegenerative disorders, and cancer.

The Impacts of Age and Sex in a Mouse Model of Childhood Narcolepsy

Narcolepsy is a sleep disorder caused by selective death of the orexin neurons that often begins in childhood. Orexin neuron loss disinhibits REM sleep during the active period and produces cataplexy, episodes of paralysis during wakefulness. Cataplexy is often worse when narcolepsy develops in children compared to adults, but the reason for this difference remains unknown. We used orexin-tTA; TetO DTA mice to model narcolepsy at different ages. When doxycycline is removed from the diet, the orexin neurons of these mice express diphtheria toxin A and die within 2-3 weeks. We removed doxycycline at 4 weeks (young-onset) or 14 weeks (adult-onset) of age in male and female mice. We implanted electroencephalography (EEG) and electromyography (EMG) electrodes for sleep recordings two weeks later and then recorded EEG/EMG/video for 24 h at 3 and 13 weeks after removal of doxycycline. Age-matched controls had access to doxycycline diet for the entire experiment. Three weeks after doxycycline removal, both young-onset and adult-onset mice developed severe cataplexy and the sleep-wake fragmentation characteristic of narcolepsy. Cataplexy and maintenance of wake were no worse in young-onset compared to adult-onset mice, but female mice had more bouts of cataplexy than males. Orexin neuron loss was similarly rapid in both young- and adult-onset mice. As age of orexin neuron loss does not impact the severity of narcolepsy symptoms in mice, the worse symptoms in children with narcolepsy may be due to more rapid orexin neuron loss than in adults.

Risk of Burn Injury in Patients With Narcolepsy: A Nationwide Population-Based Cohort Study

Narcolepsy is a rare brain disorder characterized by excessive daytime sleepiness (EDS), cataplexy, hypnagogic hallucinations, and sleep paralysis. Stimulants have been used to relieve the symptoms of EDS. Narcolepsy symptoms may pose a risk to burn injury. The study aimed to investigate the risk of burn injury in narcolepsy patients and to examine the relationship between the use of stimulants and the risk of burn injury. In all, 507 narcolepsy patients and 504 controls matched by gender, age, index year, and Charlson Comorbidity Index (CCI) score were enrolled between 1998 and 2012, then followed until the end of 2013 using Taiwan's National Health Insurance Research Database. During the follow-up period, participants who developed burn injury were identified. Cox regression analysis was used to calculate the hazard ratio (HR) with 95% confidence interval (CI) of the burn incidence rate between narcolepsy patients and unaffected controls. Narcolepsy patients had a significantly increased risk of burn injury compared to unaffected controls (5.37 versus 2.69 per 1,000 person-years, HR: 2.04, 95% CI: 1.13-3.67) after adjusting for gender, age, CCI score, urbanization degree, and duration of stimulants use. Also, the use of stimulants in narcolepsy patients was associated with a lower incidence rate of developing burn injury, but the risk estimate was not statistically significant after adjusting for the above-mentioned variables. This study shows narcolepsy patients have an increased risk of burn injury and the use of stimulants may reduce the burn incidence rate, providing a reference for developing prevention interventions.

Prevalence and incidence of narcolepsy in a US health care claims database, 2008-2010

STUDY OBJECTIVES

To determine the prevalence and incidence of narcolepsy using a large US health care claims database.

METHODS

The Truven Health MarketScan Commercial Dissertation Database (THMCDD) was used to estimate prevalence and incidence of narcolepsy, with and without cataplexy, by age groups, gender, and region among patients under age 66 years with continuous enrollment for years 2008-2010. THMCDD contains health claims information for more than 18 million people. Prevalence was expressed as cases/100 000 persons. Average annual incidence (using varying criteria for latency between the diagnostic tests, polysomnograph coupled with multiple sleep latency test [MSLT], and the diagnosis) was expressed as new cases/100 000 persons/year.

RESULTS

There were 8 444 517 continuously enrolled patients and 6703 diagnosed with narcolepsy (prevalence overall: 79.4/100 000; without cataplexy: 65.4/100 000; with cataplexy: 14.0/100 000). On the basis of the three definitions of incidence, overall average annual incidence was 7.67, 7.13, and 4.87/100 000 persons/year. Incidence for narcolepsy without cataplexy was generally several times higher than narcolepsy with cataplexy. Prevalence and incidence were approximately 50% greater for females compared to males across most age groups. Prevalence was highest among the 21-30 years age group, with incidence highest among enrollees in their early 20s and late teens. Regionally, the North Central United States had the highest prevalence and incidence, whereas the West was the lowest.

CONCLUSION

We found greater prevalence and incidence of narcolepsy (including without cataplexy) than most previous studies. The increased proportions in females, enrollees in their early 20s, and US regional differences require further study. Increased awareness and early identification is critical in the management of this burdensome condition.

Risk of bone fractures in patients with narcolepsy: a nationwide population-based cohort study

OBJECTIVES

Narcolepsy symptoms, such as excessive daytime sleepiness or cataplexy, can pose a risk to safety. Stimulants or antidepressants have been used to treat these symptoms. The study investigated the risk of bone fractures in narcolepsy patients. Also, the exposure pattern of stimulants and antidepressants to the risk of bone fractures was examined.

METHODS

In all, 493 narcolepsy patients and 490 controls matched by gender, age, index year, and comorbidity severity were enrolled between 1998 and 2012, then followed until the end of 2013 using Taiwan's National Health Insurance Research Database. During the follow-up period, participants who developed bone fractures were identified. Cox regression analysis was used to calculate the hazard ratio (HR) with 95% confidence interval (CI) for the incidence rates of bone fractures between narcolepsy patients and unaffected controls.

RESULTS

Narcolepsy patients had a significantly increased risk of bone fractures compared with unaffected controls (19.6 versus 12.3 per 1000 person-years, HR: 1.74, 95% CI: 1.29-2.35). In addition, the use of stimulants in narcolepsy patients showed lower incidence rates of bone fractures compared to non-users (incidence rates were 14.2, 11.9, and 20.0 per 1000 person-years, respectively, among frequent users, infrequent users, and non-users), but the risk estimate was not statistically significant. The evidence for associations between antidepressant use in narcolepsy patients and bone fractures was contradictory.

CONCLUSION

This study highlights the need to pay attention to the risk of bone fractures in narcolepsy patients, and the importance of adequate stimulants use might reduce the risk of bone fractures.

Cardiovascular autonomic dysfunction, altered sleep architecture, and muscle overactivity during nocturnal sleep in pediatric patients with narcolepsy type 1

Study Objectives

Arterial blood pressure (ABP) decreases during sleep compared with wakefulness and this change is blunted in mouse models of and adult patients with narcolepsy type 1 (NT1). We tested whether: (1) pediatric patients with NT1 have similar cardiovascular autonomic abnormalities during nocturnal sleep; and (2) these abnormalities can be linked to hypocretin-1 cerebrospinal fluid concentration (CSF HCRT-1), sleep architecture, or muscle activity.

Methods

Laboratory polysomnographic studies were performed in 27 consecutive drug-naïve NT1 children or adolescents and in 19 matched controls. Nocturnal sleep architecture and submentalis (SM), tibialis anterior (TA), and hand extensor (HE) electromyographic (EMG) activity were analyzed. Cardiovascular autonomic function was assessed through the analysis of pulse transit time (PTT) and heart period (HP).

Results

PTT showed reduced lengthening during total sleep and REM sleep compared with nocturnal wakefulness in NT1 patients than in controls, whereas HP did not. NT1 patients had altered sleep architecture, higher SM EMG during REM sleep, and higher TA and HE EMG during N1–N3 and REM sleep when compared with controls. PTT alterations found in NT1 patients were more severe in subjects with lower CSF HRCT-1, but did not cluster or correlate with sleep architecture alterations or muscle overactivity during sleep.

Conclusion

Our results suggest that pediatric NT1 patients close to disease onset have impaired capability to modulate ABP as a function of nocturnal wake–sleep transitions, possibly as a direct consequence of hypocretin neuron loss. The relevance of this finding for cardiovascular risk later in life remains to be determined.

Morbidity and mortality of nonepileptic seizures (NES): A controlled national study

Nonepileptic seizures (NES, psychogenic NES-PNES) are associated with significant morbidities. We evaluated the morbidities and mortality in a national group of children, adolescent, and adult patients before and after a first diagnosis of PNES.

METHODS

From the Danish National Patient Registry (1998-2013), we identified 1057 people of all ages with a diagnosis of NES and matched them with 2113 control individuals by age, gender, and geography. Comorbidities were calculated three years before and after diagnoses.

RESULTS

Patients with PNES showed increased comorbidities 3 years before and after diagnosis in almost all the diagnostic domains. The strongest associations were identified with other neurological diseases (after diagnosis, Hazard Ratio (HR): 38.63; 95% Confidence Interval (CI): 21.58-69.13; P < 0.001), abnormal clinical and laboratory findings (HR: 46.59; 95 CI: 27.30-79.52; P < 0.001), other health-related factors (HR: 12.83; 95%CI: 8.45-19.46; P < 0.001), and psychiatric comorbidities (HR: 15.45; 95% CI: 9.81-24.33). Epilepsy was identified in 8% of the patients with PNES. We found especially frequent comorbidity involving overweight, depression, anxiety, dissociative somatoform condition, other convulsions, lipothymias, reports of pain and other symptoms in several organ systems, and several reports of minimal traumas to the head, trunk, and extremities. Mortality was higher in patients with NES than in controls (HR: 3.21; 95% CI: 1.92-5.34; P < 0.001).

CONCLUSION

Morbidity is more frequent in several domains, including neurological, psychiatric, and other diseases, before and after a diagnosis of NES. Mortality is significantly higher in patients with PNES as compared to controls.

Long-term health and socioeconomic consequences of childhood and adolescent onset of meningococcal meningitis

We estimated the long-term socioeconomic consequences and health care costs of Neisseria meningitidis meningitis (NM). The prospective cohort study included Danish individuals with onset of NM in childhood and adolescence, diagnosed between 1980 and 2009. Health care costs and socioeconomic data were obtained from nationwide administrative and health registers. Two thousand nine hundred two patients were compared with 11,610 controls matched for age, gender, and other sociodemographic characteristics. In the follow-up analysis at the age of 30 years, 1028 patients were compared with 4452 controls. We found that (1) NM caused increased mortality at disease onset, but after adequate treatment, the mortality rate was similar to that of the general population; (2) neurological and eye diseases were more frequently observed in patients; (3) patients had significantly lower grade-point averages; (4) patients had lower income even when transfer payments were taken into account; and (5) patients' initial health care costs were elevated.Conclusion: NM has significant influence on mortality, morbidity, education, and income. We suggest that the management of patients with previous meningococcal meningitis should focus on early educational and social interventions to improve social and health outcomes. What is known: • Meningococcal meningitis is a severe infectious disease affecting children and adolescents with high rates of mortality and complications. What is new: • Meningococcal meningitis causes increased mortality at disease onset, but after adequate treatment the mortality rate is similar to that of the general population. • Meningococcal meningitis in childhood and adolescence has a major long-term effect on morbidity, health care costs, education, employment, and income.

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.

Cluster headache is associated with unhealthy lifestyle and lifestyle-related comorbid diseases: Results from the Danish Cluster Headache Survey

AIM

To compare the prevalence of unhealthy lifestyle factors and comorbid disorders in cluster headache patients with headache-free controls, in order to discuss pathophysiology and possible consequences.

METHODS

Cluster headache patients from the Danish cluster headache survey aged 18-65 years, diagnosed according to ICHD-II, were compared to sex- and age-matched headache-free controls. Participants completed questionnaires and structured interviews.

RESULTS

A total of 400 cluster headache patients and 200 controls participated. Patients had a more unhealthy lifestyle compared with controls in the form of current and current/former smoking (48.3% vs. 9.0%, p < 0.001 and 74.5% vs. 30.0%, p < 0.001, respectively), higher average alcohol intake per week (98.2 grams vs. 77.9 grams, p = 0.033) and BMI (26.1 vs. 24.2 kg/m², p < 0.001), whereas coffee and energy drink consumption was equally distributed. Further, lifestyle-related, psychiatric and pain-related diseases were much more prevalent in patients compared with controls, except for diabetes. Sub-group analyses revealed that current/former smokers had a worse clinical presentation than never smokers.

CONCLUSION

Unhealthy lifestyle factors and lifestyle-related diseases were more prevalent in cluster headache patients compared to controls. As lifestyle-related diseases might have serious consequences in the management of cluster headache, it is key to inform patients at an early time point about the possible risks of their lifestyle choices.

Associations Between Neuropsychological, Neurobehavioral and Emotional Functioning and Either Narcolepsy or Idiopathic Hypersomnia in Children and Adolescents

STUDY OBJECTIVES

Narcolepsy and idiopathic hypersomnia are chronic neurological sleep disorders characterized by hypersomnolence or excessive daytime sleepiness. This review aims to systematically examine the scientific literature on the associations between narcolepsy and idiopathic hypersomnia and their effect on intellectual functioning, academic achievement, behavior, and emotion.

METHODS

Published studies that examined those associations in children and adolescents were included. Studies in which children or adolescents received a clinical diagnosis, and in which the associated function was measured with at least one objective instrument were included. Twenty studies published between 1968 and 2017 were eligible for inclusion in this review.

RESULTS

There does not appear to be a clear association between intellectual functioning and narcolepsy or idiopathic hypersomnia; however, limited research is an obstacle to obtaining generalizability. The variability in results from studies investigating associations between academic achievement and these two hypersomnolence disorders suggests that further research using standardized and validated assessment instruments is required to determine if there is an association. Behavior and emotion appear to be significantly affected by narcolepsy. Only two studies included populations of children and adolescents with idiopathic hypersomnia.

CONCLUSIONS

Further research using larger populations of children and adolescents with narcolepsy or idiopathic hypersomnia while utilizing standardized and validated instruments is required, because the effect of these conditions of hypersomnolence varies and is significant for each individual.

Comorbidities in a community sample of narcolepsy

STUDY OBJECTIVE

To assess comorbidities in a community-based cohort of narcolepsy.

METHODS

A 2000-2014 community-based narcolepsy cohort was identified in Olmsted County, Minnesota. Records were reviewed by a certified sleep specialist for accuracy of diagnosis, and comorbidities were extracted and analyzed. Comorbidities in narcolepsy subjects, both at diagnosis and upon follow-up, were compared with those in unaffected and age- and sex-matched cohort using conditional logistic regression.

RESULTS

At diagnosis, there was increased association of narcolepsy with anxiety (OR 4.56, 95% CI 1.99-10.44), thyroid disease (3.07, 1.19-7.90), hypertension (2.69, 1.22-5.93), and hyperlipidemia (2.49, 1.05-5.92). At the end of the prolonged observation period of 9.9 years (SD 7.27 years), there was increased association of narcolepsy with peripheral neuropathy (11.21, 1.16-108.11), non-migrainous headache (6.00, 1.73-20.83), glucose intolerance (2.39, 1.05-5.45), and automobile-related trauma (2.43, 1.08-5.45). Persistently increased both at diagnosis and after a prolonged observation period were associations of narcolepsy with obstructive sleep apnea (OSA) (69.25, 9.26-517.99 decreasing to 13.55, 5.08-36.14), chronic low back pain (5.46, 2.46-12.11 to 2.58, 1.39-4.77), depression (4.88, 2.45-9.73 to 3.79, 2.12-6.79), psychiatric disorders in general (4.73, 2.49-9.01 to 3.40, 1.94-5.98), endocrinopathies (4.15, 1.81-9.56 to 2.45, 1.33-4.49), and obesity (2.27, 1.13-4.56 to 2.07, 1.15-3.7).

CONCLUSIONS

In this community-based study of narcolepsy comorbidities, both at diagnosis and after prolonged follow-up, persistent comorbidities were revealed, including OSA, chronic low back pain, psychiatric disorders in general, endocrinopathies, and obesity. The comprehensive management of narcolepsy requires monitoring for and managing these important associated health conditions.

The cost-utility of sodium oxybate as narcolepsy treatment

AIMS AND OBJECTIVES

Based on class-I studies, sodium oxybate is regarded as a first-line treatment for both EDS and cataplexy. The cost-effectiveness of sodium oxybate is largely unknown, though. In this study, we estimate the cost-effectiveness of sodium oxybate as treatment for patients with narcolepsy as compared to standard treatment, by calculating incremental cost-effectiveness ratios (cost per quality-adjusted life year, QALY) for patients in a Swedish setting.

MATERIALS AND METHODS

Calculations were performed using a Markov model with a 10-year time horizon. The study population consisted of adult patients treated for narcolepsy with cataplexy. Healthcare utilization and quality-adjusted life years (QALYs) for each treatment alternative were calculated assuming no treatment effect on survival. Sensitivity analyses were performed for treatment effectiveness and healthcare cost parameters.

RESULTS

The cost per additional quality-adjusted life year was estimated at SEK 563,481. The cost-effectiveness measure was demonstrated to be particularly sensitive to the duration of the relative quality-of-life improvements accruing to patients treated with sodium oxybate.

CONCLUSIONS

The estimated cost per additional QALY for the sodium oxybate treatment alternative compared with standard treatment was estimated above the informal Swedish willingness-to-pay threshold (SEK 500,000). The estimated cost per additional QALY obtained here is likely to overestimate the true cost-effectiveness ratio as potentially beneficial effects on productivity of treatment with sodium oxybate were not included (due to lack of data).