High variability of individual longitudinal motor performance over five years in very preterm infants.
Motor scores in very preterm kids improve markedly over five years, but wide individual variability means single time-point assessments can mislead.
01Research in Context
What this study did
Doctors followed 50 very preterm babies for five years.
They gave each child the same motor test at 6 months, 1 year, 2 years, 3 years, and 5 years.
The goal was to see if early scores could predict later motor skills.
What they found
On average, the group gained almost one one full standard deviation.
That means the typical child moved from the 16th percentile to the 50th.
Yet one child could jump 30 points while another stayed flat.
A single early score told almost nothing about the final outcome.
How this fits with other research
Van Keer et al. (2022) warned that infant data are messy.
Their warning matches this study: wide swings make early numbers unreliable.
Vugs et al. (2014) and Kalliontzi et al. (2022) both found large gaps between clinical and typical kids at one time point.
Those gaps look fixed, but Eussen et al. (2016) shows many preterm kids close the gap over time.
The papers do not clash—they simply capture different moments.
Cross-sectional studies show deficits; longitudinal work reveals change.
Why it matters
Do not label a preterm toddler as low-functioning from one test.
Plan to re-test every year.
Use the first score only as a baseline, not a verdict.
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02At a glance
03Original abstract
AIM: To determine longitudinal motor performance in very preterm (VPT) infants from 6 months to 5 years of age for the entire cohort of infants, according to gender and gestational age and at the individual level. METHOD: Single-center, prospective longitudinal study of 201 VPT infants (106 boys) without severe impairments. OUTCOMES: Motor performance was assessed with the Bayley Scales of Infant Development (BSID-II-MS: 6, 12, 24 months) and the Movement Assessment Battery for Children (MABC-2-NL: 5 years). RESULTS: At 6, 12, and 24 months and then at 5 years, 77%, 80%, 48%, and 22% of the infants, respectively, showed delayed motor performance (<-1SD). At 5 years, girls performed significantly better than boys in manual dexterity and balance. MIXED MODEL ANALYSES: that examined interactions between time and gender and time and gestational age, revealed no significant interactions. The variance at child level was 29%. Linear mixed model analysis revealed that mean z-scores of -1.46 at 6 months of age declined significantly to -0.52 at 5 years. Individual longitudinal motor performance showed high variability. IMPLICATIONS: Longitudinal motor performance improved almost 1 SD over five years. However, the variability of individual longitudinal motor performance hampers evaluation in clinical care and research.
Research in developmental disabilities, 2016 · doi:10.1016/j.ridd.2016.09.017