Cerebrovascular-balance relationships reveal mechanisms of neuromotor resilience to dual-task cognitive loading
BACKGROUNDAge-related decline in cerebrovascular health precipitates cognitive dysfunction and can be attenuated by habitual physical activity. Cognitive interference in balance control is well-known clinically and reflects compromised neuromotor resilience. However, whether cerebrovascular health affects cognitive-balance dual-tasking with aging is unclear. METHODSThirty participants (76{+/-}4years) completed clinical balance/cognitive testing under single-task and dual-task conditions. Balance performance was assessed as the total distance traversed during a challenging beam walking task. Cognitive performance was assessed as response time (RT) during a working-memory n-back test. Transcranial Doppler ultrasound was used to measure resting middle cerebral artery blood velocity (MCAv). We tested whether MCAv was associated with single-task and dual-task interference (DTI) in balance and cognitive performance and the effects of age and physical activity level on this relationship. RESULTSDuring single-tasking, higher MCAv associated with higher balance function (r=0.40, p=0.033), while no relationship was observed for cognitive performance. Dual-tasking strengthened relationships between MCAv and DTI across domains of balance (r=0.442, p=0.016) and cognition (r=0.328, p=0.089); for cognitive DTI, this effect was driven by individuals [≥]75years old (r=0.54, p=0.031). Individuals [≥]75years exhibited greater cognitive DTI (p=0.049), yet achieved similar balance DTI compared to those <75. Regardless of age, participants with higher MCAv demonstrated greater dual-task prioritization of balance control over cognitive performance (r=0.410, p=0.030). Physically-active participants with higher MCAv also showed less balance DTI (r=0.621, p=0.003), while there was no relationship in under-active/sedentary individuals or within the cognitive domain. CONCLUSIONSOur results support a key role of cerebrovascular health in neuromotor resilience to cognitive loading, which may emerge earlier in brain aging processes affecting balance control compared to cognition. Cerebrovascular health may support peoples ability to prioritize balance in the face of competing attentional demands, and may mediate the positive effects of physical activity on cortically-mediated balance control.