title: Survival analysis of spinal muscular atrophy type I.
abstract: OBJECTIVE
  The life expectancy of patients with spinal muscular atrophy (SMA) type I is generally considered to be less than 2 years. Recently, with the introduction of proactive treatments, a longer survival and an improved survival rate have been reported. In this study, we analyzed the natural courses and survival statistics of SMA type I patients and compared the clinical characteristics of the patients based on their survival periods.
  
  
  METHODS
  We reviewed the medical records of 14 pediatric patients diagnosed with SMA type I during a 9-year period. We examined the demographic and clinical characteristics of these patients, calculated their survival probabilities, and plotted survival curves as on the censoring date, January 1, 2010. We also compared the characteristics of the patients who died before the age of 24 months (early-death, ED group) and those who survived for 24 months or longer (long-survival, LS group).
  
  
  RESULTS
  The mean survival time was 22.8±2.0 months. The survival probabilities at 6 months, 12 months, 18 months, 24 months, and 30 months were 92.9%, 92.9%, 76.0%, 76.0%, and 65.1%, respectively. Birth weight was the only factor that showed a statistically significant difference between the ED and LS groups (P=0.048).
  
  
  CONCLUSIONS
  In this study, the survival probabilities at 2 years were far greater than expected. Because of the limited number of patients and information in this study, the contribution of improved supportive care on longer survival could not be clarified; this may be elucidated in larger cohort studies.
authors.affiliation: Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Hyun Bin
authors.initials: HB
authors.lastname: Park
authors.forename: Soon Min
authors.initials: SM
authors.lastname: Lee
authors.forename: Jin Sung
authors.initials: JS
authors.lastname: Lee
authors.forename: Min Soo
authors.initials: MS
authors.lastname: Park
authors.forename: Kook In
authors.initials: KI
authors.lastname: Park
authors.forename: Ran
authors.initials: R
authors.lastname: Namgung
authors.forename: Chul
authors.initials: C
authors.lastname: Lee