OBJECTIVES: Spinal muscular atrophy (SMA) is a rare, progressive neuromuscular disorder that causes muscle weakness and systemic disease-related complications. Utilities (measures of health-related quality of life [HRQoL]), costs and healthcare resource use (HCRU) are often reported according to SMA type; however, recent literature suggests an association between HCRU and patient motor ability. The objective of this study was to describe HRQoL and HCRU according to motor function health states of patients with SMA.

METHODS: Data from the prospective natural history study NatHis-SMA (NCT02391831) of untreated patients with Types 2 and 3 SMA (N=81) were used to estimate HRQoL and HCRU by health states reflecting the current maximum motor ability (non-sitter, sitter, stander and walker), which were defined using the Motor Function Measure (MFM) scale and ambulatory status. Mean Health Utility Index Mark 2 (HUI-2) scores at baseline were summarized by health state, SMA type, non-invasive ventilation, feeding support, scoliosis, respiratory tract infection (RTI) and sleep apnea. Prevalence of disease-related complications, HCRU and societal burden of SMA were descriptively summarized by health state. Mean HUI-2 utilities were estimated using a mixed model for repeated measures (MMRM).

RESULTS: Motor function health states and non-invasive ventilation need at baseline were significantly associated with HRQoL. Baseline values for disease-related complications were 0.46 (non-invasive ventilation), 0.38 (feeding support), 0.54 (scoliosis), 0.58 (RTI) and 0.50 (sleep apnea). Disease burden, HCRU, caregiver and patient productivity loss, and missed social activities were highest for patients lacking higher motor capabilities. Mean HUI-2 utilities estimated by a MMRM were 0.49 (non-sitters), 0.54 (sitters), 0.56 (standers) and 0.84 (walkers). Non-invasive ventilation need was associated with a disutility of –0.04.

CONCLUSIONS: Motor function health states of patients with Types 2 and 3 SMA, as defined by MFM, are significantly related to SMA disease burden, including HRQoL, disease-related complications, HCRU and societal impact.