Relationship of factors affecting age of onset of independent ambulation.

Despite the standard available pediatric developmental scales and popular lore that girls walk at an earlier age than boys, no large-scale evaluation of the age of onset of independent ambulation has been previously published. The purpose of this study was the prospective epidemiologic evaluation of a large heterogeneous group of normal children to determine the effect of gender, race, birth order, and socioeconomic status on the age of onset of independent ambulation. The study cohort consisted of 986 children (575 male, 471 female). A multivariable analysis of covariance model was used to examine the effects of race, gender, income, and birth order on age at ambulation. After controlling for the other variables in the model, race was the only statistically significant predictor of age at ambulation (p < 0.0001), with black children walking at a younger age (10.9 +/- 2.1 months) than white children (11.6 +/- 2.3 months). Overall, the independent variables included in the model were only able to explain 2.5% of the variance of age at ambulation.