Associations of cardiorespiratory fitness with structural and load-dependent large artery stiffness in older adults.

Aging is associated with progressive large artery stiffening, which can be from structural (changes in the arterial wall) or load-dependent (higher blood pressure) mechanisms. Greater cardiorespiratory fitness (CRF) is associated with lower large artery stiffness, yet whether the beneficial relationship is from structural or load-dependent components remains unclear. Older adults (n=799, 72±5 years; 59.2% female) with CRF estimated via a 400m walk test (minutes) and aortic large artery stiffness assessed via carotid-femoral pulse wave velocity (cfPWV, m/s) were included in this cross-sectional analysis. Using participant-specific exponential models, aortic stiffness was standardized to a reference blood pressure to separate structural and load-dependent stiffness mechanisms. In linear regression adjusted for common cardiovascular disease risk factors, greater CRF (per minute) was associated with lower total cfPWV [B (95% CI), -0.23 m/s (-0.41,-0.05)] and structural cfPWV [-0.26 m/s (-0.45,-0.07)]. CRF was not associated with load-dependent cfPWV [0.03 m/s (-0.01,0.07)]. Stratified analyses suggest associations were strongest in males and participants aged ≥70 years (interaction p<0.05). In conclusion, higher CRF is associated with lower structural, but not load-dependent, aortic stiffness in older adults, suggesting the vascular benefits of CRF may reflect long-term attenuation of arterial wall remodeling rather than blood pressure driven mechanisms. By distinguishing structural and load-dependent components, this study offers a more precise understanding of how CRF relates to vascular aging than analyses relying on total cfPWV alone in older adults. Maintaining CRF, particularly into later life, may be an effective way to slow vascular aging and preserve health of the cardiovascular system.