The association of early linear growth and haemoglobin concentration with later cognitive, motor, and social-emotional development at preschool age in Ghana.

It is important to identify the periods during childhood when exposure to environmental risk factors results in long-term neurodevelopmental deficits. Stunting and anaemia may be sensitive indicators of exposure to such risks. In a prospective cohort enrolled before birth, we investigated the association of developmental scores at 4-6 years with (a) birth length and linear growth during three postnatal periods and (2) haemoglobin (Hb) concentration at three time points. Children were participants in a follow-up study of a randomized controlled trial of nutritional supplementation in Ghana. At 4-6 years, cognitive, motor, and social-emotional developments were assessed using standard tests adapted for this population. We estimated the associations of length-for-age z-score (LAZ) at birth and postnatal linear growth (n = 710) and Hb (n = 617) with developmental scores in regression models, using multistage least squares analysis to calculate uncorrelated residuals for postnatal growth. Cognitive development at 4-6 years was significantly associated with LAZ at birth (β = 0.12, 95% CI = 0.05, 0.19), ΔLAZ from 6 to 18 months (β = 0.16, 95% CI = 0.04, 0.28), and Hb at 18 months (β = 0.13, 95% CI = 0.06, 0.20), but not with ΔLAZ during 0-6 months, ΔLAZ from 18 months to 4-6 years, Hb at 6 months, or Hb at 4-6 years. No evidence of associations with motor or social-emotional development were found. These results suggest that in similar contexts, the earlier periods prior to birth and up to 18 months are more sensitive to risk factors for long-term cognitive development associated with LAZ and Hb compared with later childhood. This may inform the optimal timing of interventions targeting improved cognitive development.