Survival analysis and life expectancy of pediatric patients with spinal muscular atrophy in Thailand

Background: Survival data for Thai patients with 5q spinal muscular atrophy (SMA), the leading cause of infant mortality worldwide, are lacking. Objective: This study aimed to determine the survival rates and life expectancies of pediatric patients with SMA types 1, 2, and 3. Methods: We conducted a retrospective cohort analysis of genetically confirmed 5q SMA patients aged 0-18 years who were treated between 1999 and 2021 at the pediatric neuromuscular clinic of Siriraj Hospital, Bangkok, Thailand. Mortality data were sourced from the Civil Registration Office. Results: The study included 113 patients: 37 with SMA type 1, 53 with type 2, and 23 with type 3. Life expectancy varied significantly by SMA type: 2.2 years for type 1, 11 years for type 2, and 16.5 years for type 3. The median survival times for SMA type 1 and 2 were 1.9 and 19 years, respectively. In SMA type 2, early onset (<1 year) correlated with a shorter median survival than later onset (>= 1 year) (log-rank test P = 0.009). Early onset SMA type 2 had a median survival time of 15.9 years, while 75 % of those with later onset SMA type 2 survived until the age of 19 years. Cox proportional hazards analysis revealed that each month's delay in disease onset reduced the annual mortality risk by 17 % for type 1 patients and by 20 % for type 2 patients. Compared with female patients, male patients with type 2 disease had a 12-fold increased mortality risk. Conclusions: Age at onset is a significant predictor of survival and life expectancy in patients with SMA types 1 and 2. These insights are crucial for genetic counseling and prognostic discussions in clinical settings.