Respiration during sleep in children with spinal muscular atrophy type 2 and 3, treated with nusinersen or risdiplam

Spinal muscular atrophy (SMA) is associated with sleep-disordered breathing (SDB) and sleep-hypoventilation in children. Weakened intercostal muscles and preserved diaphragm strength cause thoraco-abdominal asynchrony (TAA) during sleep in this group. Our aim was to study if disease-modifying treatment (DMT) could stabilise or improve sleep-related respiration in children with SMA type 2 or 3 over a four-year period. We followed 34 children and adolescents with SMA type 2 or 3 who initiated either of the DMTs nusinersen or risdiplam between 2017 and 2023. Respiratory polygraphy was performed at treatment start and repeatedly for 4 years. Respiratory outcomes were measured, including TAA prevalence, expressed as the percentage of total sleep time (TST) with a phase angle >40° between thorax and abdomen. Median follow-up was 3.6 years. Use of non-invasive ventilation was unchanged throughout the study. In SMA type 2, AHI decreased by 5.1 [95%CI -7.6 to -2.6] and the obstructive-AHI and oxygen desaturation index showed a similar decrease, while minimal-SpO₂ increased by 4.2% [0.2 to 8.2]. In SMA type 3 no change was seen in the above factors, but TAA prevalence decreased by 14.1% [-25.3 to -2.9] from the baseline value of 34.5% of TST. The proportion of subjects with abnormal TAA, defined as >10% TST, fell from 86.7% to 40.0%. Over the study period, DMTs were associated with stabilization or improvement of sleep-related respiration in both SMA type 2 and 3. This included reduced SDB in type 2 and improved TAA in type 3, with no evidence of respiratory decline.