2.8. Statistical Analysis
REGRESSION, SECONDARY
A total of 156 children were included in the final statistical analysis. For each of these children, one visit between the ages of 3 and 5 years where neurodevelopmental testing was performed and 25(OH)D concentrations were measured was analyzed. Results were described using the mean and standard deviation for continuous variables and the median for integers and for situations where data were not normally distributed. Results were considered significant if The primary outcome measures of this study were neurodevelopmental assessment scores on the Brigance Screen in association with the treatment group. The secondary endpoint, VDBP genotype and its relationship with neurodevelopmental scores, was also assessed. Linear regression was used to evaluate these outcome measures. Variables were first examined in univariate models and were controlled for in multivariate models if univariate analysis was significant. We then reduced the model to include only those variables that were significant in multivariate analysis into a final, fully reduced model. Treatment groups remained in all multivariate models, including the fully reduced model, regardless of significance due to study design. Parameters measured included offspring birth 25(OH)D concentration, offspring 25(OH)D concentration at the time of testing (3–5-year follow-up visit), maternal college education, maternal marital status, sex of the child, breastfeeding status, race, small for gestational age, season at the time of testing (3–5 years old), insurance, and VDBP genotype. Additionally, maternal 25(OH)D concentration both at baseline and prior to delivery was correlated with offspring 25(OH)D at birth.