Effect of Aerobic Exercise on Cerebral Blood Flow and Cognitive Function in Persons with Down Syndrome

Down syndrome (DS), the leading genetic condition of intellectual disability, is associated with high risk of cognitive decline, dementia, and Alzheimer’s disease (AD). Cognitive decline with dementia and AD hinders not only the wellbeing of individuals with DS, but also the independence of the aging population with DS. Cognitive function is related to brain perfusion, with higher pulsatile blood flow having a detrimental effect on brain microvasculature. Exercise can improve cerebral blood flow and cognitive function in individuals without DS. However, it is unknown if the cerebral blood flow (CBF) characteristics are related to cognitive function in individuals with DS at rest and post exercise. Thus, we investigated the difference in cognitive function and CBF and its relationship in individuals with and without DS. We further investigated the effects of a single bout of moderate intensity aerobic exercise on cognitive function and CBF in these individuals. Cognitive function and CBF characteristics were measured before, immediately after, and 30 minutes following a 20 minute bout of moderate intensity treadmill walking. Cognitive function was significantly lower (p<0.05) in individuals with DS and both the cerebral artery pulsatility index (PI) and resistance index (RI) were significantly higher in individuals with DS compared to controls (p<0.05 for all). However, mean middle cerebral artery blood flow velocity (mMCAv) was not different between groups (p>0.05). Exercise did not alter the cognitive function (p>0.05) or mMCAv (p>0.05) in individuals with DS. Individuals without DS exhibited significant improvement in cognitive function following exercise (p<0.05). Time of completion for the cognitive task was not related to CBF velocity (r= -0.085, p=0.61), but was inversely related to aerobic capacity (r= -0.411, p=0.01) in the overall cohort. However, these correlations were no longer significant when the analysis was conducted within the DS group and control group separately. Our data show that cognitive function was not related to CBF velocity. Moderate intensity exercise did not improve CBF velocity and cognitive function in individuals with DS, whereas individuals without DS showed significant cognitive function improvement. Furthermore, individuals with DS are more exposed to pulsatile blood flow, which may be detrimental to the cerebral vasculature.