Lower-limb physical function is associated with executive function in frail older adults.

Frailty reflects an accumulation of health deficits across multiple physiological systems. Better physical function is associated with higher executive function, but it remains unclear if frailty influences this relation. This study tested if the association between physical performance and executive function in older adults would be stronger among frailer persons. It also sought if cerebral oxygenation is associated with these factors. Sixty older adults (72 ± 6 years; n = 11 male) were divided into non-frail (frailty index, < 0.10; n = 31) and very-mild + frailty (frailty index, ≥ 0.10; n = 29) based on a 34-item index. Physical function was assessed via the six-minute walk test (6MWT), chair stand test (30CST), grip strength (HGT), and 8-foot up-and-go test (8FUGT). Executive function was measured using a computerized Stroop task, and prefrontal cortex oxygenation was assessed via functional-near-infrared spectroscopy. 6MWT, 30CST, and 8FUGT, but not HGT (p = 0.08), were better in the non-frail compared to the very-mild + frailty groups (all, p < 0.02). In the very-mild + frailty group, greater 6MWT distance and better 30CST performance were associated with faster reaction time on inhibition and switching (all, p < 0.003). No such associations were observed in the non-frail group, nor with 8FUGT or HGT among the very-mild + frailty group (all, p > 0.08). Overall prefrontal cortex oxygenation during the switching condition was higher in non-frail versus very-mild + frail participants (p = 0.04), but adjusting for oxygenation did not change relations between 6MWT or 30CST and executive functions in frailer persons. The association between lower-limb physical performance and executive function was stronger in older adults with accumulated health deficits.