1 INTRODUCTION
Spinal muscular atrophy (SMA) is an autosomal recessive disease caused by deletion or mutation of the survival motor neuron 1 (SMN1) gene with progressive muscle atrophy, weakness and paralysis. The incidence rate of live births is approximately 1/11000. SMA in children is classified into types 1-3 depending on the age of onset and maximal motor milestone achieved.1 SMA is the primary genetic disease leading to the death of children under two years old, and respiratory failure is the most common cause of death.2 Nocturnal hypopnea is the first respiratory problem in SMA, subsequently developing into daytime hypopnea. Early pulmonary function can still be compensated. However, patients are very prone to acute respiratory failure (ARF) once pulmonary infection occurs. The more severe the case, the more likely children are to have various respiratory complications, including sleep-disordered breathing, recurrent pneumonia and ARF.2,3 Appropriate and effective strategies of respiratory management are crucial to stabilize lung function and reduce the incidence of respiratory complications and mortality in children with SMA. The literature and expert opinion support using a sleep study to confirm when a patient has sleep-disordered breathing and needs to use noninvasive ventilation to prevent recurrent respiratory tract infections (RRTIs) and ARF. In addition, nutritional assessment and intervention are also related to respiratory management.2,4 However, there is still no specific standard to evaluate and intervene in these respiratory problems. Therefore, the aim of the present study was to obtain the risk factors for RRTI and/or ARF and the specific values in children with SMA. This is the largest study of polysomnography (PSG) in children with SMA reported thus far.