Prevalence and associations of sleep disordered breathing in children with neuromuscular disorders.

<bold>Introduction:</bold> Sleep disordered breathing (SDB) includes obstructive sleep apnoea (OSA), central sleep apnoea (CSA) and hypoventilation. We determined prevalence of SDB and associated factors in children with neuromuscular disorders. <bold>Methods:</bold> Children had laboratory polysomnogram (PSG) and available clinical data. Hypoventilation was defined as pCO2 >50mmHg for >25% total sleep time, OSA as an obstructive apnoea hypopnoea index >1.0/hr, CSA as a central apnoea hypopnoea index >5.0/hr. Cross sectional associations between SDB, age, diagnosis, ambulation and BMI z-score were examined using chi squared or Mann Whitney U tests. <bold>Results:</bold> There were 66 children aged 6.0-16.7 (median 11.5) years, 73% were male. There were 27 with Duchenne Muscular Dystrophy, 18 with Spinal Muscular Atrophy, 8 with congenital muscular dystrophy and 12 with congenital myopathy. Median BMI z-score was -0.24, 55% could ambulate. Of 13 (20%) who used NIV, 10 wore NIV during the entire PSG. At least one type of SDB was present in 52% (n=34), OSA in 32% (n=21), hypoventilation in 18% (n=12) and CSA in 14% (n=9). Hypoventilation was more likely in children with congenital myopathy compared to other diagnoses (p=0.049) and children with a lower BMI z-score (median -0.03 vs. -0.63, p=0.008). OSA was more likely in individuals who were unable to ambulate (p=0.007) and older children (median 11.3 years vs. 12.4 years, p=0.046). <bold>Conclusions:</bold> The prevalence of SDB was high in this cohort and likely under-estimated because some used NIV during PSG. The findings reflect the heterogeneity of the cohort and suggest that there are individual risk factors for each type of SDB, such as underlying diagnosis, BMI z-score and age.