Original ArticleObstructive sleep apnea in narcolepsy
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.
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2021, Sleep Medicine ReviewsCitation Excerpt :In the case of OSA, the contributory role of disordered breathing related to symptoms associated with narcolepsy (DNS and EDS [66]) is likely to be underestimated, particularly in middle-aged people with established disease. It has been estimated that OSA is found in 24%–40% of adult patients with narcolepsy [67–69]; however, EDS was similar regardless of comorbid OSA in all studies [67–69]. It is unknown whether cardiovascular risk is increased by comorbid OSA in people with narcolepsy.
Impact of Intrinsic Sleep Disorders on Sleep Disordered Breathing
2021, Encyclopedia of Respiratory Medicine, Second Edition
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Present address: Neurology Service, Hospital Parc Tauli, Sabadell, Spain.