Abstract 18689: Lower Carotid Artery Compliance and Greater Carotid β-stiffness Index are Associated With Slower Processing Speed and Reduced Working Memory Performance in Older Healthy Adults

Abstract

Introduction: Higher central elastic artery stiffness is associated with greater brain white matter hyperintensity volume and lower cognitive performance in older adults. However, it is unknown if higher central artery stiffness is related to regional decreases in brain white matter integrity (WMI) and reductions in working memory or processing speed. We hypothesized that greater large elastic artery stiffness would be associated with lower working memory and slower processing speed as well as lower regional WMI in older adults. Methods: In young (n=19; 23.8 ± 0.7 yrs) and older (n=22; 64.4 ± 4.2 yrs; range 60-71 yrs) healthy adults, aortic stiffness (carotid-femoral pulse wave velocity, cfPWV, via tonometry) and carotid artery compliance and β-stiffness index (carotid artery ultrasound and tonometry) were determined non-invasively. WMI was assessed by fractional anisotrophy (FA) (3T MRI) from diffusion tensor images. An N-Back task and letter and pattern comparison tests were performed as measures of working memory and processing speed, respectively. d’Prime, a measure of signal detection, was calculated on the N-Back task as a ratio of positive ‘hits’ to ‘false alarm’ responses. Results: cfPWV (8.4 ± 0.5 vs. 5.2 ± 0.2 m/sec, P<0.01) and carotid β-stiffness (11.3 ± 0.9 vs. 6.1 ± 0.7 U, P<0.01) were greater and carotid compliance (0.16 ± 0.02 vs. 0.07 ± 0.01 mm/mmHg, P<0.01) was lower in older vs. young adults. Carotid β, but not aortic, stiffness was associated with slower processing speed on letter (10.7 ± 0.5 vs. 13.5 ± 0.6 units/ 30 sec, p<0.01) and pattern (16.6 ± 0.6 vs. 22.0 ± 0.7 units/30 sec, p<0.01) comparison tasks and reduced working memory (1.8 ± 0.2 vs. 3.1± 0.2, P<0.01) in older vs. young adults. Lower carotid compliance was associated with slower performance on the letter (r=0.55, P<0.01) and pattern (r=0.54, P<0.01) tests and lower d’Prime (r=0.48, P<0.05). Greater β-stiffness was related to pattern comparison scores only (r=-0.54, P<0.01). Aortic stiffness, carotid compliance and β-stiffness were not related to WMI in any brain region. Conclusions: Our results suggest that lower carotid artery compliance and greater β-stiffness are associated with reduced working memory performance and slower processing speed but not regional WMI in older adults.