Objective: To examine the relationship between characteristics of the cognitive environment at age 10 to 18 months and vocabulary at age 18 to 30 months.
Design: Analysis of baseline and follow-up data on 157 families participating in a comparison of 2 anticipatory guidance programs.
Setting: Children's Hospital outpatient department serving low-income families.
Participants: Parents of children aged 10 to 18 months at baseline who participated in a follow-up telephone interview at age 18 to 30 months.
Main outcome measures: Three subscales of the StimQ (reading, parental involvement in developmental activities, and parental verbal responsivity [PVR]) and the short form of the MacArthur Communicative Development Inventories.
Results: Vocabulary score percentiles dropped significantly between baseline and follow-up, with scores for bilingual families showing a greater decrease than those for English speaking-only families. StimQ subscale scores increased with maternal education and increased between baseline and follow-up. Multiple regression analysis showed that baseline variables accounted for 25% of the variance in follow-up vocabulary score percentile, with significant contributions from baseline expressive vocabulary (P < .001), PVR (P = .01), and home language (P = .03) scores. Seventy-seven percent of children with PVR scores less than 4 had follow-up vocabulary scores at or less than the 25th percentile, with an associated likelihood ratio of 4.33. However, 35% of children with a PVR score of 4 also had vocabulary scores less than the 25th percentile at follow-up, with an associated likelihood ratio of 0.67.
Conclusions: The StimQ is a clinically useful method for assessing early environmental factors that influence vocabulary development. The PVR subscale score was the best StimQ predictor of later vocabulary delay and may be useful in identifying children needing referral for evaluation.