This study examined central artery stiffness and hemodynamic pulsatility during cognitive engagement in younger and older adults.Methods
Vascular-hemodynamic measures were completed in 19 younger (age 35 ± 1 yrs) and 20 older (age 69 ± 2 yrs) adults at rest and during a Stroop task. Aortic stiffness (carotid-femoral pulse wave velocity, PWV) and carotid pulse pressure (PP) were assessed using applanation tonometry. Carotid stiffness was assessed as a single-point PWV using Doppler Ultrasound. Middle cerebral artery (MCA) mean flow and flow pulsatility index (PI) were assessed using transcranial Doppler. Cognitive function was assessed as accuracy and reaction time from the Stroop task.Results
Older adults had lower accuracy scores and longer reaction times on the Stroop task compared to younger adults (p < 0.05). Both age groups had similar increases in MCA mean flow during Stroop (p < 0.05). There were significant increases in aortic PWV, carotid PWV, carotid PP and MCA PI during Stroop in older but not younger adults (p < 0.05). Carotid PP and MCA PI assessed during Stroop were statistical mediators of the association between age group and Stroop performance metrics (accuracy and reaction time, p < 0.05), while aortic and carotid PWV were indirect statistical mediators of MCA PI through carotid PP (p < 0.05).Conclusions
Older adults experience increases in large artery stiffness during cognitive engagement possibly preventing effective buffering of pulsatile hemodynamic energy entry into the cerebrovasculature. This is important as pulsatile flow during cognitive engagement, and not mean flow per se, was related to overall cognitive performance.