Prevalence and characteristics of sleep-disordered breathing in familial dysautonomia

Abstract

Objective: Familial dysautonomia (FD) is an autosomal recessive disorder characterized by impaired development of sensory and afferent autonomic nerves. Untreated sleep-disordered breathing (SDB) has been reported to increase the risk of sudden unexpected death in FD. We aimed to describe the prevalence and characteristics of SDB in FD.

Patients/methods: Seventy-five patients with FD (20 adults and 55 children) underwent in-lab polysomnography, including peripheral capillary oxygen saturation (SpO₂) and end-tidal capnography (EtCO₂) measurements. A t-test and Spearman's correlation analysis were performed to evaluate the impact of age on sleep, occurrence of apneas, SpO₂ and EtCO₂ levels; and to determine the relationship between apneas and SpO₂/EtCO₂ measurements during different sleep stages.

Results: Overall, 85% of adults and 91% of pediatric patients had some degree of SDB. Obstructive sleep apneas were more severe in adults (8.5 events/h in adults vs. 3.5 events/h in children, p = 0.04), whereas central apneas were more severe (10.8 vs. 2.8 events/h, p = 0.04) and frequent (61.8% vs. 45%, p = 0.017) in children. Overall, a higher apnea-hypopnea index was associated with increased severity of hypoxia and hypoventilation, although in a significant fraction of patients (67% and 46%), hypoxemia and hypoventilation occurred independent of apneas.

Conclusion: Most adult and pediatric patients with FD suffer from some degree of SDB. There was a differential effect of age in the pattern of SDB observed. In some FD patients, hypoventilation and hypoxia occurred independently of apneas. Therefore, we recommend including EtCO₂ monitoring during polysomnography in all patients with FD to detect SDB.

Keywords: EtCO(2); Familial dysautonomia; Polysomnography; Sleep-disordered breathing; SpO(2).

Fig. 1

Discordance between sleep apneas and hypoxemia/hypoventilation in familial dysautonomia. Although in many patients (both adults and children), sleep apneas were accompanied by oxygen desaturation (average SpO₂ levels < 92% in children and < 90% in adults) and/or hypoventilation (maximum EtCO₂ levels > 50% in children and > 55% in adults), in a significant number of them that was not the case. The y-axis depicts percentage of patients.