The Down Syndrome Profile Emerges Gradually Across Early Development.
Hana D'Souza, Annette Karmiloff-Smith, Denis Mareschal and 1 others
In 101 children with Down syndrome aged 6–63 months, gross motor and expressive language fall further behind over time, while receptive language keeps up.
Don't use walking or talking as a shortcut to judge overall ability.
Key findings
1The profile of relative strengths and weaknesses in DS is uneven and changes over development: gross motor is a persistent area of weakness, expressive language becomes an emerging weakness, and receptive language becomes an emerging strength.
2Children with DS gain new abilities as they get older (age-equivalent scores increase across all domains), but in most domains they do so at a slower pace than typically developing children (developmental quotient scores decrease with age), with receptive language being the exception.
3In the longitudinal follow-up, only visual reception showed stable individual differences over time; no other domain met the significance threshold. The authors note the longitudinal sample (37 children) may have been too small to detect associations in other domains.
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What it does not show
The primary design is cross-sectional: children of different ages are compared at one time point, so the 'change over time' is inferred from between-child differences, not from watching the same child grow. The longitudinal validation subset (37 children) was too small to detect most stability effects; the authors estimate a sample five times larger would be needed for adequate power. The MSEL norms are approximately 30 years old and were not established for children with Down syndrome, so standard scores hit the floor and the authors had to rely on age-equivalent scores, which have their own interpretive limits. A child with DS at an age-equivalent of 24 months does not necessarily have the same abilities as a typically developing 24-month-old; the test may miss abilities the child uses (e.g., Makaton) and may over-penalise atypical performance patterns. The sample is from the UK LonDownS cohort; 80.8% were identified as White, which limits generalisability. Three children in the cross-sectional sample and six in the longitudinal sample were excluded for reaching ceiling on one or more scales, so the findings may not apply to children whose abilities exceed the MSEL range.
Declared interests
Funded by the Wellcome Trust, Waterloo Foundation, Baily Thomas Charitable Fund, Jerome Lejeune Foundation, UK Research and Innovation, and the James S. McDonnell Foundation. The authors state the funding bodies had no role in study design, data collection, analysis, interpretation, writing, or the decision to publish. No conflicts of interest declared.
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