Association between head circumference at two years and second and fifth year cognition.

Background: Head circumference (HC) measurement is routinely not performed in early childhood and there is conflicting information about its utility in literature. The current study analyses the association between HC at two years of age and cognition at two and five years of age.
Methods: A community based birth-cohort recruited between 2010 and 2012 was followed up till five years of age in an urban slum in Vellore, India. Children were recruited at birth after informed parental consent by consecutive sampling using eligibility criteria of healthy new-born, singleton pregnancy and family's availability in the study area during follow-up. HC measured at two years of age was used as the exposure variable to calculate association with cognition at both two and five years of age. Cognitive domain of Bayley scale of infant development was used at two years of age and Wechsler Preschool Primary Scales of Intelligence at five years.
Results: Of the 251 enrolled children, 138 (55%) were girls and 71 (30%) belonged to lower socioeconomic status. At 2 years, 8.81% of children had HC < - 3SD. Compared to children with HC z-scores ≥ - 2 SD, those with measurements < - 3 SD had a lower cognition scores by - 2.21 [95% CI: - 3.87 - -0.56] at 2 years. Also, children with HC < - 3 SD at two years scored significantly lower scores in cognitive domains of verbal, - 7.35 [95% CI: - 11.78 - -2.92] and performance, - 7.07 [95% CI: - 11.77 - -2.36] intelligence at five years.
Conclusions: This study showed that smaller HC at 2 years of age was negatively associated with cognition at both 2 and 5 years of age. Early childhood HC measurements can be utilised as a cheaper screening tool to identify children at risk in LMIC settings. Further studies can confirm these findings in diverse settings.