The association between cerebral blood flow and standing dual task performance is dependent upon age group and cognitive load

Postural control, especially when standing and performing cognitive "dual tasks," requires effective regulation of cerebral blood flow (CBF) to support functional neural activation within involved brain networks. Aging from adulthood into senescence diminishes dual task performance and CBF. However, it is unknown whether CBF obtained during dual task execution correlates with performance, or if age influences the nature of this relationship. Twenty-three relatively healthy younger (26 ± 3 years) and 24 older (76 ± 6 years) adults completed the n-back task of executive function (i.e., identify X [IdX] and 2-back) while standing. CBF of the middle cerebral artery was measured using transcranial Doppler ultrasound and postural control (i.e., elliptical area, range, and path length) was recorded using a wearable motion sensor. N-back task performance was reported as the Balanced Integration Score (BIS). During the IdX task, the relationship between CBF and postural control was dependent upon age (p = 0.03). Within the younger group, the association between CBF velocity and path length was slightly negative, but nonsignificant. This association, however, was opposite (i.e., positive) in the older group. There was no association between CBF and BIS for the IdX task. During the higher demanding 2-back task, greater CBF was associated with longer path length irrespective of age group (p = 0.03), yet lower BIS (more efficiency) for the 2-back in older adults only. These results indicate that dual task postural control is reliant on CBF, yet the nature of this relationship may be dependent upon both age and difficulty of the cognitive task.