Sleep apnea in adult myotonic dystrophy patients who have no excessive daytime sleepiness.

PURPOSE: Sleep apnea is common in myotonic dystrophy (MD) and may cause respiratory failure. Most of the sleep studies have been performed in patients with excessive daytime sleepiness (EDS), which is a characteristic and strong predictor of sleep apnea. Therefore, we investigated the prevalence of sleep apnea in adult MD patients who have no EDS.

MATERIALS AND METHODS: Epworth Sleepiness Scale was used to exclude EDS and a score over 10 was accepted as an indicator of EDS. Sleep studies of 17 adult MD patients with the Epworth sleepiness scale score < or =10 were retrospectively reviewed. Spirometry (n = 16) and daytime arterial blood gasses were used to evaluate the relationship with nocturnal parameters.

RESULTS: On admission to the outpatient chest clinic, seven patients had normal spirometry, and ten had daytime hypercapnia and/or hypoxemia. All but one had sleep apnea (apnea-hypopnea index > or =5 events/h of sleep; mild in five, moderate in seven, and severe in four). Hypopneas were more common than apneas (16.9 +/- 13.2 events/h vs. 4.6 +/- 4.1 events/h). Nocturnal desaturation episodes were very frequent (oxygen desaturation index, 19.7 +/- 20.3/h of sleep). Three patients had central sleep apnea and 13 had obstructive sleep apnea. Body mass index, spirometry parameters (FVC and FEV1) and arterial oxygen tension were moderately correlated with nocturnal oxygenation parameters. Apnea-hypopnea index showed moderate correlation with spirometry parameters (FVC and FEV1).

CONCLUSION: Sleep apnea and oxygen desaturations are very common in MD patients who report no excessive daytime sleepiness. Daytime lung function parameters are not sufficiently reliable for screening sleep apnea. Therefore, we recommend routine polysomnography in MD patients.