Predictors of respiratory decline in neuromuscular disorders

Neuromuscular diseases (NMDs) constitute a heterogeneous group of genetic and acquired disorders that lead to progressive muscle weakness. When the respiratory muscles are involved, impaired ventilation and ineffective airway clearance become a major source of morbidity and mortality. Respiratory insufficiency is one of the major contributors to mortality in NMDs, with considerable variation in onset and rate of progression across different diseases. Patients with NMD have progressive weakness of the diaphragm and accessory respiratory muscles. This weakness leads to reduced chest wall compliance and restrictive lung disease. In some NMDs, bulbar dysfunction results in impaired airway clearance and aspiration pneumonia. Despite advances in care, predicting the onset of respiratory decline in NMDs remains a major clinical challenge. This narrative review aims to synthesize the current evidence on predictors of respiratory decline in NMDs. We comprehensively evaluate a broad spectrum of clinical, physiological, cellular, imaging, genetic, and digital markers that have emerged as predictors for respiratory decline in NMDs. These include age-related trends, pulmonary function tests, strength assessments, advanced imaging modalities, blood and serum biomarkers, genetic variants, scoring systems, and emerging smartphone based tools. By highlighting these factors, we underscore their potential to improve the early detection of respiratory impairment and guide timely interventions.