Weight gain, dietary intake, and body composition in patients with Type 2 and Type 3 SMA

Children with spinal muscular atrophy (SMA) types 2 and 3 are at risk for overweight and increased body fat. Research objectives were to determine whether increased caloric or fat intake were associated with weight increases across percentile curves over a 1 year period and to support alternative methodology for growth assessment. This retrospective, observational study used data collected at the University of Utah. Data were reviewed one visit prior to weight increases and at subsequent visits. Dietary data from type 2 (N=16) and type 3 (N=4) participants ages 0-18 years old were analyzed. Growth status assessment included only children with type 2 SMA (N=20). Assessments used weight-for-age percentiles, 3-day diet records and food analyses. Modified Hammersmith Functionality Scores and Compound Muscle Action Potential tracked disorder progression. Body fat percentages from dual energy x-ray absorptiometry (DXA) were compared to National Health and Nutrition Examination Survey (NHANES) percentile data and body mass index (BMI) percentiles on the Centers for Disease Control and Prevention (CDC) growth charts. Mixed-effect analysis was used to evaluate correlations between weight increases and both diet and disorder progression. Descriptive analysis was used to assess growth chart status and body fat composition. Statistical significance was set at p<0.05. There was no statistical difference in dietary intake associated with weight increases. Disorder progression was not statistically different between visits. The majority of participants were obese with body fat percentages greater than the NHANES 95th percentile at the first and last visits (12 of 20 and 19 of 20, respectively). Results indicate that rapid weight gain in children with SMA is a product of disorder progression and not dietary alterations. Children with SMA may plot normally on the CDC BMI growth charts despite a high percent body fat. Alternative methodology for growth assessment in this population is required.