Executive function deficit in preschool children born very low birth weight with normal early development

Background: Many studies showed that children born very low birth weight (VLBW) are at high risk of executive function (EF) deficit, including impulse control, working memory and cognitive flexibility. However, they did not exclude the influence of abnormal early development on EF deficit. Aims: The aim was to investigate if six-year-old VLBW children with normal early development still have EF deficit. Methods: The research was conducted in two groups. The VLBW group included 37 children at aged 6, with more than 70 of Bayley Scales of Infant Development-Second Edition (BSIDII) before aged 2. The normal group included 22 term children aged 6 who were born healthy and developed normally, with comparable IQ and social economic status. Five instruments, including Comprehensive Nonverbal Attention Test Battery (CNAT), Tower of London (ToL), Wisconsin Card Sorting Test (WCST), Knox's Cube Test and Digit Span Subtest of WISC-IV, were analyzed to evaluate four kinds of EF, including impulse control, planning, cognitive flexibility and working memory. Results: The EF of VLBW group was significantly lower in independent t-test on the scores of planning in ToL, cognitive flexibility in WCST and nonverbal working memory in Knox's Cube Test. Yet, the inferiority in EF of VLBW group became less significant when ANCOVA analysis was used to adjust gestation age and birth weight. Conclusions: Six-year-old VLBW children even with normal early development are still at risk of deficits in "planning", "cognitive flexibility" and "nonverbal working memory" while the preterm factors, both gestation age and birth weight, were important covariant factors.