Head circumference in ELBW babies is associated with learning difficulties and cognition but not ADHD in the school-aged child

Abstract

This study examines whether a small head circumference (HC) and low head-circumference growth velocity (HGV) during the first year of life predict consequences at school age in learning, cognition, and concentration. A total of 124 extremely-low-birthweight (ELBW) infants (birthweight 500 to 999 g) born between 1977 and 1986 were eligible for follow-up at the corrected ages of 4, 8, and 12 months and 2, 4, and 6 years. Infants were categorized as having a small HC (< 3% or 3 to 10%) on the basis of the 1990 British growth data which allowed standardized z-scores to be calculated for HC, independent of gestation and corrected age. HGV measurements were calculated using differences in the HC z-scores. In 1995, parents of 87 children agreed to participate in a study of learning and attention at school age. Attention-deficit-hyperactivity disorder (ADHD) was assessed using the Du Paul Rating Scale. Academic performances were based on a teacher questionnaire dealing with aspects of reading, writing, mathematics, and spelling. A child was considered to have a learning difficulty if academic problems were present in at least one of these four areas. Intellectual ability was assessed using the McCarthy Scale at 6 years. HC < 3% and 3 to 10% at 8 months' corrected age was strongly associated with school-aged learning problems (P=0.004), with a moderate specificity (70%), positive predictive value (PPV) (67%), and sensitivity (67%). HGV < or = 10% from birth to 4 months was also associated with learning problems at school age (P=0.01) with a higher specificity (98%) and PPV (88%) but lower sensitivity (20%). A logistic regression analysis was performed with the risk for learning difficulties at 8 months as the dependent variable. Sex, gestation, birthweight, multiple births, and a history of intraventricular hemorrhage did not substantially alter the unadjusted odds ratio (4.7; 95% CI 1.9 to 13.6). Maternal age and education did not confound the relation. No association was found between HC or HGV and ADHD. HC < 3% at 4 months (P<0.02), 8 months (P=0.02), and 12 months (P=0.04), and HGV between birth and 4 months (P<0.01) were significantly associated with low cognitive ability at 6 years.