Forty-two adolescents with Down syndrome (DS) ages 10 to 21 years completed a battery of language and phonological memory measures twice, 2 years apart. Individual differences were highly stable across two years. Receptive vocabulary scores improved, there was no change in receptive or expressive grammar scores, and nonword repetition scores declined. Digit memory and expressive vocabulary scores improved among younger adolescents, but generally held steady among older adolescents. These patterns may reveal key points in development at which interventions may be best applied. Further research is needed to understand specific processes in tasks that appear to be slowing or declining during adolescence. They may be important for understanding early aging and dementia in DS.

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Sustained attention (SA) and short-term memory (STM) contribute to language function in Down syndrome (DS). We proposed models in which relations of SA to language in DS are mediated by STM. Thirty-seven youth with DS aged 10–22 years (M = 15.59) completed SA, STM, and language tasks. Cross-sectional mediation analyses were run with the bootstrapping method. We found significant indirect effects of SA separately on vocabulary and syntax through auditory STM with point estimates of −.30 and −.31, respectively. Results suggest lapses in SA compromise auditory STM, which in turn impacts vocabulary and syntax in youth with DS; however, further research is needed to confirm causality. Addressing SA and STM in language therapy with youth with DS could lead to improved outcomes.

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