CONTRIBUTION OF COGNITIVE INTERFERENCE TO DECREMENTS IN WALKING PERFORMANCE IN HEMODIALYSIS PATIENTS

Abstract

Patients with advanced CKD have impaired walking function that predisposes them to falls and disability. Deficits in walking function are traditionally ascribed to declines in physical function. However, walking impairment in certain clinical populations may also result from a phenomenon known as cognitive-motor interference. This is characterized by reductions in motor task performance (e.g., walking speed) when simultaneously performing a cognitive task, and is termed a dual task cost (DTC). The purpose of this study was to compare the contribution of cognitive interference to decrements in walking performance in hemodialysis patients and healthy controls. 14 hemodialysis patients (10M,4F, age=48.5+/-11.8) and 14 age-matched healthy controls (9M, 5F, age=48.5+/- 10.1) participated. Each completed a walking task in a control and dual task condition. The walking task involved walking at a comfortable pace 4 times across a 26’GAITRite TM mat. The first 2 trials were completed with no cognitive task and the last 2 trials with a simultaneous task that consisted of generating a modified word list. Walking performance was quantified with normalized gait speed, step length, base of support, and step time. DTC was determined for each variable as the % difference in performance between the single task and dual task. Major metrics of walking function under standard conditions were impaired by 20-40% in hemodialysis patients vs controls (p<0.05 for each.). In addition, CKD patients had a greater DTC for velocity, cadence, step time and double support, than the control group (p<0.05), and trends for greater DTC for step length and width (p = 0.07). These data indicate that walking impairments in hemodialysis patients are not due exclusively to declines in physical function, but that cognitive-motor interference also plays a significant role. This has significant clinical importance, as therapies designed to improve walking performance and physical function, such as nutritional and exercise interventions, may need to be augmented with cognitive training in order to have maximum benefits.