Brain Structure in Older Adult Siblings

Considerable variability exists in patterns of brain aging within and across individuals. Quantifying familial contributions to brain structure in late life may help us understand this variability. We estimated heritability of gray and white matter volumes and cortical thickness in a sample of older adult full siblings (2-4 individuals per pedigree; N = 75). Estimation of heritability was based on computation of intraclass correlations. Heritability estimates were higher for total cortical thickness compared to volumes. There was no evidence of overall laterality in heritability estimates, or differences between primary sensory and association regions. There was a tendency for lower estimates of heritability in the frontal lobe relative to other lobes, but greater estimates for amygdala and hippocampus relative to parahippocampus and for caudate relative to putamen and globus pallidus. Strong heritability was observed across callosal regions. This study provides a comprehensive assessment of heritability of brain structure in older adults.