Heritability of Head Size in Dutch and Australian Twin Families at Ages 0–50 Years

Abstract

We assessed the heritability of head circumference, an approximation of brain size, in twin-sib families of different ages. Data from the youngest participants were collected a few weeks after birth and from the oldest participants around age 50 years. In nearly all age groups the largest part of the variation in head circumference was explained by genetic differences. Heritability estimates were 90% in young infants (4 to 5 months), 85–88% in early childhood, 83–87% in adolescence, 75% in young and mid adulthood. In infants younger than 3 months, heritability was very low or absent. Quantitative sex differences in heritability were observed in 15- and 18-year-olds, but there was no evidence for qualitative sex differences, that is, the same genes were expressed in both males and females. Longitudinal analysis of the data between 5, 7, and 18 years of age showed high genetic stability (.78 > RG> .98). These results indicate that head circumference is a highly heritable biometric trait and a valid target for future GWA studies.

Genetics of head circumference in infancy: A longitudinal study of Japanese twins

“…A moderate common environmental effect, i.e., 0.25, was still found at 3-5 months of age, whereas after the fifth month of age they were small and statistically nonsignificant. Consistently to our results, common environmental effect was found from birth to 3-5 months of age, but disappeared after that, in Dutch (Smit et al, 2010) and Taiwanese twin cohorts (Chen et al, 1990). It is possible that estimates of common environmental factors at birth and soon after that reflect special features of twin pregnancies (Buckler and Green, 2004), which may explain the decreasing effect of common environment soon after birth.…”

Covariation between human pelvis shape, stature, and head size alleviates the obstetric dilemma

“…Given the high heritability of stature (24,31,32), we therefore also predict that the stronger obstetric selection pressure on shorter women has led to a pelvis with a birth canal that is more shaped toward obstetric demands in comparison with taller women.…”

Brain development and scholastic achievement in the Education Quality Measurement System tests in Chilean school-aged children

“…Genes influencing the variability in both cognition and brain plasticity partly drive these associations. Thus, not only does the brain continue to change well into adulthood, but these changes are functionally relevant because they are related to intelligence (18); this has been described as the best predictor of scholastic achievement (SA) (19).…”

“…Heritability estimates were greater than 80% from young infants to adolescence (18). However, environmental factors, such as maternal level of education, home environmental stimulation, and type of school attended, plus birth HC and growth in head size in the first 6 mo, have been described by many authors as significant determinants for cognition (4).…”