Evidence is limited regarding clinical factors associated with ambulation status over the lifespan of individuals with myelomeningocele. We used longitudinal data from the National Spina Bifida Patient Registry to model population-level variation in ambulation over time and hypothesized that effects of clinical factors associated with ambulation would vary by age and motor level.
A population-averaged generalized estimating equation was used to estimate the probability of independent ambulation. Model predictors included time (age), race, ethnicity, sex, insurance, and interactions between time, motor level, and the number of orthopedic, noncerebral shunt neurosurgeries, and cerebral shunt neurosurgeries.
The study cohort included 5371 participants with myelomeningocele. A change from sacral to low-lumbar motor level initially reduced the odds of independent ambulation (OR = 0.24, 95% CI = 0.15–0.38) but became insignificant with increasing age. Surgery count was associated with decreased odds of independent ambulation (orthopedic: OR = 0.65, 95% CI = 0.50–0.85; noncerebral shunt neurosurgery: OR = 0.65, 95% CI = 0.51–0.84; cerebral shunt: OR = 0.90, 95% CI = 0.83–0.98), with increasing effects seen at lower motor levels.
Our findings suggest that effects of several commonly accepted predictors of ambulation status vary with time. As the myelomeningocele population ages, it becomes increasingly important that study design account for this time-varying nature of clinical reality.
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