Dynamics of Cognitive Delay Between 24 and 48 Months of Age

Cognitively delayed children are at risk for poor mental and physical health throughout their lives. The economically disadvantaged and some race/ethnic groups are more likely to experience cognitive delay, but trajectories of delay in early childhood and underlying mechanisms responsible for disparities are not well understood. The objectives of this research are to quantify patterning of sociodemographic disparities in cognitive functioning between 24 and 48 months of age, and to identify predictors of low cognitive functioning. Data come from 7,289 children in the Early Childhood Longitudinal Study, Birth Cohort (ECLS-B). Of the 988 children classified as cognitively delayed at 24 months, only 240 (24%) remained delayed at 48 months, while 748 children who tested in the normal range at 24 months had low cognitive scores by 48 months. This suggests a high rate of improvement for some children, and conversely increasing risk for many others. Multiple logistic regression analyses were conducted to examine associations between low cognitive functioning at 48 months and sociodemographic characteristics and gestational and birth-related factors among those children who experienced declining scores over time. The strongest predictor of low cognitive functioning was socioeconomic status, which showed a strong and inverse gradient—the lower the SES quintile, the higher the risk of cognitive delay. Other significant predictors included nonwhite race/ethnicity and being born very prematurely. Further investigation of processes whereby social disadvantage adversely affects development in early childhood is needed to guide interventions to eliminate disparities.