Age-associated sex and asymmetry differentiation in hemispheric and lobar cortical ribbon complexity across adulthood: A UK BioBank Imaging Study

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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 non-linear 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.
Original languageEnglish
Pages (from-to)49-65
Number of pages17
JournalHuman Brain Mapping
Issue number1
Early online date15 Sept 2022
Publication statusPublished - 1 Jan 2023

Bibliographical note

This research has been conducted using the UK Biobank resource. This work was supported by the Aberdeen Biomedical Imaging Centre with financial support from the Roland Sutton Academic Trust (RSAT-0067/R/19). The authors would like to thank the participants of the UK Biobank imaging study and our colleague Dr Naif Majrashi for performing image pre-processing using Freesurfer


  • Ageing
  • Cortical complexity
  • Hemispheric asymmetry
  • sexual dimorphism
  • Cortex
  • Fractal dimension
  • MRI


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