BACKGROUND AND PURPOSE: Exercise plays an important role in supporting overall brain health. However, the mechanisms by which exercise supports brain health are imprecisely defined. Further, brain hemodynamic changes during exercise are not clearly understood, especially in older adults. The primary aim of this study was to compare cerebral blood flow velocity and pulsatility index (PI) during moderate-intensity exercise between older adults with normal pulsatile flow (normal PI) and older adults with elevated pulsatile flow (elevated PI). Secondary aims were to compare cardiovascular disease risk and cognitive function between individuals with elevated and nonelevated PI. METHODS: Using transcranial Doppler ultrasound (TCD), middle cerebral artery blood velocity (MCAv) and PI were recorded during the rest and moderate-intensity exercise. End tidal carbon dioxide (P CO ) and beat-to-beat mean arterial blood pressure were also recorded. RESULTS: We enrolled 104 older adults into the study. The change in PI was greater in normal PI group (35.5% vs. 21.3%, P = .005). The change in MCAv was similar in both groups (11.6% for normal PI vs. 10.6% for elevated PI; P = .22). There was no significant difference in cardiovascular disease risk between the two groups (P = .77). Individuals with elevated PI performed significantly worse in WAIS-R Digit Symbol and Trail Making Test A (P = .04 and = .01, respectively). CONCLUSIONS: The percent increase in PI from rest to moderate-intensity exercise was attenuated in the older adults with elevated resting PI. Higher resting PI may negatively affect brain health as evidenced by the slower processing speed scores.
