Sleepiness and sleep disordered breathing in Prader-Willi syndrome: relationship to genotype, growth hormone therapy, and body composition.

STUDY
OBJECTIVES: Patients with Prader-Willi syndrome (PWS) suffer from excessive sleepiness and sleep disordered breathing (SDB). We reviewed the polysomnograms (PSGs) and multiple sleep latency tests (MSLTs) in a cohort of PWS patients to determine the relationship of BMI(Z) scores, daytime sleepiness, growth hormone (GH) treatments, and SDB.
METHODS: Attended overnight PSGs were performed for PWS patients referred for concern for SDB between January 2000 and January 2005. Age at time of study, genotype, use and dose of GH, sleepiness scale, normalized body-mass index (BMI(Z)), total sleep time, latency to stage I and REM sleep, sleep stage percentages, apnea-hypopnea index (AHI), central apnea (CA) frequency, oxygen saturation nadir, maximum carbon dioxide tension, periodic limb movement index, presence of snoring, normality of EEG, and, in several patients, mean sleep latency testing were determined.
RESULTS: All patients exhibited some form of SDB. There was a positive correlation between the BMI(Z) and AHI. The BMI(Z) was significantly different between GH-treated and -untreated groups, but there was not a significant difference between AHI, CA, oxygen nadir, or maximum carbon dioxide tension of the GH-treated and -untreated groups. There was no significant correlation between the MSLT and the sleepiness scale or AHI. There was also no significant difference between the AHIs of patients with different genetic defects.
CONCLUSIONS: There should be a low threshold for obtaining PSG to evaluate SDB, but the type and severity of SDB were not predictable based on a sleepiness scale score, BMI(Z), or underlying genetic defect.