Geometric Aging of the Thoracic Aorta: Insights From 2 Large Cohorts.

BACKGROUND Aortic structural degeneration occurs with aging; however, 3-dimensional geometric remodeling has not been well characterized in large populations. METHODS We segmented the thoracic aorta from magnetic resonance images of 56 164 UKB (UK Biobank) participants and computed tomography images of 9417 PMBB (Penn Medicine Biobank) participants. We quantified structural measurements of elongation, dilation, tortuosity, and curvature across the thoracic aorta. Multivariate linear regression models estimated the associations between age and aortic structure in a subset of normative healthy participants from the UKB (n=3532), and in the overall cohorts. RESULTS Patterns of aging were highly consistent between the UKB and PMBB. In the UKB normative subset, aging was associated with profound geometric changes, including elongation (β per decade of age, 1.001 cm [95% CI, 0.893-1.110]; P<0.0001), luminal dilation (β per decade of age, 0.870 mm [95% CI, 0.794-0.947]; P<0.0001), and decreased curvature (β per decade of age, -0.060 mm-1 [95% CI, -0.067 to -0.053]; P<0.0001). The strongest relationship with age was observed for aortic volume (β per decade of age, 17.124 mL [95% CI, 15.124-18.386]; P<0.0001). No age-sex interactions were observed in the healthy normative subset, whereas in the overall UKB and PMBB cohorts, females exhibited less pronounced luminal dilation (particularly after menopause) and more pronounced changes in curvature. CONCLUSIONS Aging is associated with profound 3-dimensional geometric changes in the thoracic aorta, including elongation, luminal dilation, and decreased curvature. Females demonstrate less eccentric aortic remodeling and more pronounced changes in curvature, likely contributing to unfavorable pulsatile arterial hemodynamics that are present in older females.