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The changing natural history of spinal muscular atrophy type 1

From the Departments of Neurology (M.O., J.O., D.C.D.V., P.K.), Pediatrics (M.O., J.O., D.C.D.V.), and Biostatistics (G.L.), Columbia University, New York, NY; and Department of Medical and Molecular Genetics (C.J.G., J.M.G.), Indiana University School of Medicine, Indianapolis, IN.

Address correspondence and reprint requests to Dr. Petra Kaufmann, 180 Fort Washington Ave., HP-5, New York, NY 10032 pkaufmann{at}neuro.columbia.edu

Background: Noninvasive ventilation has become increasingly available to spinal muscular atrophy (SMA) patients since the early 1990s. This is expected to have improved survival for SMA type 1 patients.

Objective: To assess whether there has been a change in survival in patients with SMA type 1 between 1980 and 2006.

Methods: We used deidentified, family-reported data from participants in the International Spinal Muscular Atrophy Patient Registry and obtained additional clinical information through a mail-in questionnaire. One hundred forty-three patients with SMA type 1 were included in the analysis. Survival of patients born in 1995–2006 (n = 78) was compared with that of patients born in 1980–1994 (n = 65), using the Kaplan–Meier method and Cox proportional hazards models with age at death as the outcome.

Results: Patients born in 1995 though 2006 had significantly increased survival compared with those born in 1980–1994 (log-rank test, p < 0.001). In a Cox model, patients born in 1995–2006 had a 70% reduction in the risk of death compared with those born in 1980–1994 (hazard ratio [HR] 0.3, 95% CI 0.2–0.5, p < 0.001) over a mean follow-up of 49.9 months (SD 61.1, median 22.0). However, when controlling for demographic and clinical care variables, year of birth was no longer significantly associated with age at death (HR 1.0, 95% CI 0.6–1.8, p = 0.9), whereas ventilation for more than 16 h/d, use of a mechanical insufflation–exsufflation device, and gastrostomy tube feeding showed a significant effect in reducing the risk of death.

Conclusion: Survival in spinal muscular atrophy type 1 patients has increased in recent years, in relation to the growing trend toward more proactive clinical care.

GLOSSARY: BiPAP = bilevel positive airway pressure; HR = hazard ratio; MI-E = mechanical insufflation–exsufflation; SMA = spinal muscular atrophy; YOB = year of birth.

Supported by the Spinal Muscular Atrophy (SMA) Foundation (P.K., M.O., J.O., D.C.D.V.); Families of SMA (International SMA Patient Registry); and NIH CTSA Award 1 UL1 RR024156-01 (P.K.).

Disclosure: The authors report no conflicts of interest.

Received February 26, 2007. Accepted in final form May 25, 2007.