Is excessive daytime sleepiness characteristic of Prader-Willi syndrome? The effects of weight change

Objectives: To assess nighttime and daytime sleep patterns in patients with Prader-Willi syndrome and to examine the effects of weight change on excessive daytime sleepiness in patients with this disorder. Design: Case series (within-subject design). Setting: A university sleep disorders center. Patients: Eight patients (5 males and 3 females), ranging in age from 5.5 to 21 years, who met the diagnostic criteria for Prader-Willi syndrome. Interventions: Overnight sleep polysomnographic recording and daytime Multiple Sleep Latency Test. Four of the 8 patients were restudied after their weight had changed. Main Outcome Measure: Changes in the sleep disordered breathing rate and Multiple Sleep Latency Test measures. Results: Sleep-disordered breathing occurred in all patients and was principally characterized by obstructive hypoventilation or episodes of apnea that occurred primarily during rapid eye movement sleep. After weight reduction, 3 patients had respiratory values that were within the broad normal range (disordered breathing rate, <15 breaths per hour). Statistically significant (P<.05) weight loss effects occurred during nonrapid eye movement sleep (decrease with weight loss, F=6.243). Excessive daytime sleepiness was documented in 6 of 7 patients who completed the Multiple Sleep Latency Test. Excessive daytime sleepiness was not consistently correlated with body weight or any of the nocturnal sleep variables. Conclusions: A sleep-related breathing disorder occurred during rapid eye movement and nonrapid eye movement sleep and improved with weight change in patients with Prader-Willi syndrome, emphasizing the importance of weight reduction in clinical management. However, excessive daytime sleepiness persisted despite a reduction in sleep-disordered breathing after weight loss, suggesting a primary disturbance of sleep. Our findings provide additional support for the view that primary hypersomnia is a characteristic feature of the Prader- Willi syndrome.