Diminished Locomotor Control Is Associated With Reduced Neurovascular Coupling in Older Adults.

BACKGROUND: Walking, especially while dual-tasking, requires functional activation of cognitive brain regions and their connected neural networks. This study examined the relationship between neurovascular coupling (NVC), as measured by the change in cerebral blood flow in response to performing a cognitive executive task, and dual-task walking performance.
METHODS: Seventy community-dwelling older adults aged 84 ± 5 years within the Maintenance of Balance, Independent Living, Intellect and Zest in the Elderly (MOBILIZE) Boston Study were divided into LOW (n = 35) and HIGH (n = 35) NVC. NVC was quantified by transcranial Doppler ultrasound and stratified by the median change in cerebral blood flow velocity of the middle cerebral artery induced by the performance of the n-back task of executive function. Walking metrics included walking speed, step width, stride length, stride time, stride time variability, and double-support time from single- and dual-task walking conditions, as well as the "cost" of dual-tasking.
RESULTS: During both single- and dual-task walking, older adults with LOW NVC displayed narrower step width (p = .02 and p = .02), shorter stride length (p = .01 and p = .02), and longer double-support time (p = .03 and p = .002) when compared with the HIGH group. During single-task walking only, LOW NVC was also linked to slower walking speed (p = .02). These associations were independent of age, height, hypertension, atrial fibrillation, and assistive device. The LOW and HIGH NVC groups did not differ in dual-task costs to walking performance.
CONCLUSION: In older adults, diminished capacity to regulate cerebral blood flow in response to an executive function task is linked to worse walking performance under both single- and dual-task conditions, but not necessarily dual-task costs.