Morbidity Risk across the Lifespan for Adults with Spinal Muscular Atrophy: A Retrospective Cohort Study

Abstract

Background: Recently approved treatments for spinal muscular atrophy (SMA) may shift clinical care priorities to secondary complications associated with SMA-related aging. To date, there is little knowledge about the natural history of morbidities across the adult lifespan for SMA. The objective of this study was to identify the risk of various morbidities among adults with vs. without SMA prior to SMA-related treatment. Methods: This was a retrospective cohort study that accessed Medicare fee-for-service and commercial claims data from 01/01/2008-12/22/2016. Data from adults ≥ 18-years-old with SMA and without SMA matched (1:200 case:control) on demographics, region, and study entry year were included. The prevalence of 30 morbidities across physiologic systems (e.g., cardiovascular, metabolic, musculoskeletal, urinary) and mental health disorders was examined. Age-and sex-adjusted odds ratio (OR) was estimated using logistic regression for each morbidity and effect modification by age and sex was tested. Results: There were 2,427 adults with SMA (mean [SD] age, 59.7 [17.4] years; 49.0% female) and 484,528 matched adults without SMA. Adults with vs. without SMA had a higher prevalence and adjusted OR of all 30 morbidities, ranging from OR = 1.61 (95% CI = 1.45-1.80) for hypothyroidism to OR = 7.80 (95% CI = 7.10-8.57) for fluid/electrolyte disorders. There was effect modification by age for 24 morbidities. The OR was highest for the youngest age group (18-40 years; OR range, 2.38 to 117.7; all P < 0.05) and declined with older age groups, but still remained significantly elevated in the oldest age group (≥ 75 years; OR range, 1.30 to 5.96; all P < 0.05). Conclusion: The limitations of this study are that evidence of morbidities were limited to diagnostic claims and information on SMA type and symptoms or onset were not available. In conclusion, adults with SMA had a higher and earlier risk of a variety of morbidities across physiological systems and mental health disorders.