Background: Birthweight is associated with cognition and educational attainment across the full birthweight range in the normal population, independently of social background. However, the extent to which birthweight reflects fetal growth, or is a marker of subsequent size, with respect to this association, is not clear. We therefore investigated the independent effects of birthweight and postnatal height adjusted for postnatal weight on cognitive function and educational attainment while controlling for family background.
Methods: Using the British 1946 birth cohort we investigated the association between cognitive function at various ages and birthweight, height adjusted for weight in childhood and adulthood, and educational attainment, controlling for sex, father's social class, maternal education, birth order, and maternal age.
Results: Birthweight was positively associated with cognition up to age 26, and with the likelihood of obtaining advanced educational qualifications. Height was positively associated with cognition at all ages, and also with educational attainment. Weight was not associated with cognition at ages 8 and 15, but was negatively associated with verbal ability at age 26, with verbal memory at age 43, and with educational attainment. These effects were independent of each other, and of family background. Conditional analyses suggested the positive effect of height growth on cognition at two intervals, one in early childhood, and the other in late adolescence. In addition, weight gain after age 15 was negatively associated with cognition at 26.
Conclusion: Birthweight and postnatal growth are independently associated with cognition.