Elsevier

Sleep Medicine

Volume 11, Issue 1, January 2010, Pages 93-95
Sleep Medicine

Original Article
Obstructive sleep apnea in narcolepsy

https://doi.org/10.1016/j.sleep.2009.02.009Get rights and content

Abstract

Study objectives

Narcolepsy and obstructive sleep apnea syndrome (OSAS) are two conditions associated with excessive daytime sleepiness (EDS). They may coexist in the same patient but the frequency of this association and its clinical significance is unknown. The presence of obstructive sleep apnea (OSA) in a narcoleptic patient may interfere with the diagnosis of narcolepsy. The aim of the study was to determine the prevalence of OSA in narcolepsy.

Design and setting

University hospital sleep clinic series of narcoleptic patients diagnosed with nocturnal polysomnography and multiple sleep latency test. Patients were systematically interviewed evaluating narcoleptic and OSAS features and their response to continuous positive airway pressure (CPAP) treatment when applied.

Patients

One hundred and thirty-three patients with narcolepsy.

Results

Thirty-three patients (24.8%) had an apnea–hypopnea index greater than 10 with a mean index of 28.5 ± 15.7. Ten of them were initially diagnosed only with OSAS and the diagnosis of narcolepsy was delayed 6.1 ± 7.8 years until being evaluated in our center for residual EDS after CPAP therapy. In the remaining 23 patients, narcolepsy and OSA were diagnosed simultaneously. Cataplexy occurred with similar frequency in both groups. EDS did not improve in 11 of the 14 patients who were treated with CPAP. The presence of OSA was associated with male gender, older age and higher body mass index.

Conclusions

OSA occurs frequently in narcolepsy and may delay the diagnosis of narcolepsy by several years and interfere with its proper management. In patients with OSA, cataplexy should be actively looked for to exclude the presence of narcolepsy. Treatment with CPAP does not usually improve EDS in narcoleptics with OSA.

Introduction

Narcolepsy is a neurological disorder with a prevalence of 0.03–0.16% [1] characterized by excessive daytime sleepiness (EDS), cataplexy, sleep paralysis and hypnagogic hallucinations. In most cases multiple sleep latency test (MSLT) shows two or more sleep onset periods (SOREMPs). Cataplexy is the most characteristic symptom occurring in 65–75% of the patients and EDS is usually the most disabling feature. EDS in narcolepsy, however, may not always be distinguished from the sleepiness caused by other disorders such as obstructive sleep apnea syndrome (OSAS) [2].

OSAS is a much more prevalent disorder occurring in 2–4% of the adult population [3], whereas EDS is one of the major presenting complaints [2]. In OSAS, increased body mass index (BMI) is a frequent finding that leads to upper airway obstruction causing breath cessation during sleep. Narcolepsy is also associated with increased BMI [3], [4] which may predispose one to comorbid obstructive sleep apnea (OSA). Narcolepsy and OSAS may be confounded because (1) both disorders are associated with EDS and increased BMI, and (2) MSLT in patients with OSAS may occasionally show two or three SOREMPs [5], [6].

Due to the high prevalence of OSA, a large number of patients presenting to sleep centers with EDS are evaluated with nocturnal sleep studies only to confirm the presence of sleep disordered breathing. Thus, it is possible that narcoleptics with comorbid OSA presenting to sleep centers with EDS may be diagnosed with OSAS alone and that narcolepsy is overlooked. In the current study we aimed to determine the prevalence of OSA in a large series of narcoleptics diagnosed in our sleep center. We also assessed how many narcoleptics were initially diagnosed only with OSAS before presenting to our sleep center and the effect of continuous positive airway pressure (CPAP) on EDS when applied.

Section snippets

Methods

We evaluated 133 consecutive narcoleptics, diagnosed according to ICSD-2 criteria [2] presenting to our center with EDS between 1991 and 2007. All patients underwent polysomnography and a 5-nap MSLT the following day. A definite history of cataplexy was present in 104 patients. We included patients without cataplexy and an AHI > 10 only when they had four or five SOREMPs in the MSLT [5], [6] or low hypocretin-1 (<110 pg/mL) in the CSF.

At the time of this study all patients were contacted and

Results

We evaluated 133 consecutive patients with a mean age of 38.6 ± 16.4 (range, 11–80) years. Eighty-eight (66%) were male and 45 (34%) female. The mean BMI was 23.9 ± 4.7. Polysomnography showed an AHI  10 in 33 (24.8%) patients with a mean of 28.5 ± 15.7 (Fig. 1). In all of them apneas were obstructive except in two patients who had predominantly central apneas (AHI of 14 and 40, respectively). Patients with AHI  10 were significantly more often men, older and had a higher BMI than those with AHI < 10 (

Discussion

This is the first study evaluating sleep apnea in a large series of patients with narcolepsy and the effect of CPAP therapy in narcoleptics with comorbid OSA.

Previous studies assessing the prevalence of OSA in narcolepsy are scarce and reported results ranging between 2% and 68%. Guilleminault et al. [9] noted two patients with narcolepsy and central sleep apnea. Laffont et al. [10] described the occurrence of sleep apnea in five patients. One had central apneas, one had obstructive apneas and

Disclosure statement

This work is not an industry supported study. Dr. Sansa, Iranzo and Santamaria indicate no financial conflicts of interest.

References (20)

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1

Present address: Neurology Service, Hospital Parc Tauli, Sabadell, Spain.

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