Age‐associated sex and asymmetry differentiation in hemispheric and lobar cortical ribbon complexity across adulthood: A UK Biobank imaging study

Abstract

Cortical morphology changes with ageing and age‐related neurodegenerative diseases. Previous studies suggest that the age effect is more pronounced in the frontal lobe. However, our knowledge of structural complexity changes in male and female brains is still limited. We measured cortical ribbon complexity through fractal dimension (FD) analysis at the hemisphere and lobe level in 7010 individuals from the UK Biobank imaging cohort to study age‐related sex differences (3332 males, age ranged 45–79 years). FD decreases significantly with age and sexual dimorphism exists. With correction for brain size, females showed higher complexity in the left hemisphere and left and right parietal lobes whereas males showed higher complexity in the right temporal and left and right occipital lobes. A nonlinear age effect was observed in the left and right frontal, and right temporal lobes. Differential patterns of age effects were observed in both sexes with relatively more age‐affected regions in males. Significantly higher rightward asymmetries at hemisphere, frontal, parietal, and occipital lobe level and higher leftward asymmetry in temporal lobe were observed. There was no age‐by‐sex‐by asymmetry interaction in any region. When controlling for brain size, the leftward hemispheric, and temporal lobe asymmetry decreased with age. Males had significantly lower asymmetry between hemispheres and higher asymmetry in the parietal and occipital lobes than females. This work provides distinct patterns of age‐related sex and asymmetry differences that can aid in the future development of sex‐specific models of the normal brain to ascribe cognitive functional significance of these patterns in ageing.

Brain asymmetries from mid- to late life and hemispheric brain age

“…Both GM volume, surface, and thickness show asymmetries across studies 1,3,4,9,54 . We identified lower asymmetry linked to higher ages in the ventricular and pallidum volumes, appearing alongside the known effect of larger ventricle volumes at higher ages 55 .…”

“…Considering all regional features, LRTs on GAMs (Eq. 4, 3) indicated that all features were age-sensitive ( p < 5.1 × 10 − 71 ). LRTs on linear models (Eq.…”

“…However, previously outlined brain asymmetries [1][2][3][4][5][6] might be informative for age predictions. One way of leveraging brain asymmetries into simple metrics is to estimate separate brain ages for each hemisphere (HBA) and to then compare the estimates.…”

“…Yet, the influence of hemispheric differences or brain asymmetry on the age predictions remains unclear. However, previously outlined brain asymmetries 1–6 might be informative for age predictions. One way of leveraging brain asymmetries into simple metrics is to estimate separate brain ages for each hemisphere (HBA) and to then compare the estimates.…”

Modeling Brain Functional Connectivity Patterns during an Isometric Arm Force Exertion Task at Different Levels of Perceived Exertion: A Graph Theoretical Approach

“…In this work, we consider sex as a factor, as previous findings have suggested sex and hormone-based differences in brain networks when comparing male and female individuals [ 62 , 63 ] and due to the limited number of EEG-based studies on female participants only [ 13 , 64 ]. Furthermore, recent studies support “the importance of considering sex as a biological variable in brain research” [ 65 ] for the future development of sex-specific models to ascribe cognitive functional significance [ 66 ] and an understanding of sex-related diseases [ 67 ]. We also calculated the most commonly used global and local graph theory measures for two frequency bands (alpha and beta).…”