Published Online First

Objectives To determine: (a) prevalence of clinically unsuspected nocturnal hypoventilation (NH) in a clinic population of children with progressive neuromuscular disease; (b) whether NH can be predicted from clinical/ laboratory parameters; and (c) change over 1 year in pulmonary function decline, quality of life and attention in children with NH treated with non-invasive positive pressure ventilation (NPPV) compared with children without NH. Design Prospective cohort study. Setting Two tertiary-care paediatric neuromuscular clinics. Patients 46 children (6–17 years) with progressive neuromuscular disease without neurocognitive impair-ment or dystrophinopathy. Interventions Polysomnography, pulmonary function, manual muscle strength, quality of life (CHQ-PF50) and Conners questionnaires. Outcome measures (a) Prevalence of NH; (b) predic-tive value of surrogate clinical measures for NH; and (c) differences in change over 1 year in pulmonary function, muscle strength, quality of life and attention between children with and without NH. Results Prevalence of NH was 14.8%, 95 % CI 8.0% to 25.7%. Maximal sensitivity and specifi city for NH were achieved with thresholds of forced vital capacity <70 % and forced expiratory volume in 1 s <65 % pre-dicted (sensitivities: 71.4, 71.4; specifi cities: 64.1, 79.5). Scoliosis also predicted NH (sensitivity 88.9; specifi city 80.4). Over 1 year, those with NH had a greater increase in residual volume/total lung capacity (0.075 (−0.003 to 0.168) vs −0.03 (−0.065 to 0.028)), decline in muscle strength (−0.67 (−0.90 to 0.10) vs 0.53 (−0.05 to 0.90)) and worsened perception of health status. Conclusions 15 % of subjects had clinically unsuspected NH, predicted by moderate pulmonary function test impairment and scoliosis. Over 1 year those with NH had increased gas trapping, decline of muscle strength and worse perception of health status, despite NPPV