Physical Performance in Adults with Chronic Kidney Disease

Abstract

Background and Purpose. Chronic kidney disease (CKD) and dialysis dependent end stage renal disease (ESRD-D) are associated with reduced physical performance and functional mobility, though associated factors are not well understood. The overarching purpose of this dissertation is to explore questions related to physical performance in CKD /ESRD-D with 3 studies. “The Relationship of Fatigue with Physical Performance and Mobility Disability in Chronic Kidney Disease“ aimed to examine the association of fatigue with physical performance and mobility disability in adults with CKD (stages 2-4). “Reliability of Physical Performance and Instrumented Measures in Adults with Kidney Disease” aimed to assesses the reliability of physical and inertial sensor measurement units (IMUs) in adults with CKD and ESRD-D and compare differences between these groups. “The Acute Effects of Dialysis on Physical Performance in Adults with Hemodialysis Dependent End Stage Renal Disease” aimed to examine differences in physical performance that occur immediately after a dialysis session and assess the association of dialysis-related factors to observed change. Methods. To assess relationships between physical performance, fatigue, and mobility disability, a cross-sectional study of 293 adults with CKD (stages 2-4) was conducted. Physical performance measures included the short physical performance battery (SBBP), Five Times Sit to Stand (FSTS), gait speed, 6 Minute Walk Test (6MWT) and handgrip strength (HGS). Fatigue was assessed with the SF-36 Energy-Fatigue-Vitality Subscale (SF-EF). Regression analysis was conducted to assess the relationship of fatigue to each physical performance measure controlling for age, BMI, and CKD-related factors. Logistic regression, controlling for age, BMI, and CKD-related factors, assessed the relationship of fatigue and mobility disability (defined by the inability to walk ¼ mile and/or climb 1 flight of 10 steps) based on established cut-points on the SPPB, gait speed and FSTS. Test-retest reliability was assessed 1-week apart in a group of 21 CKD (n=11) and ESRD-D (n=10) patients on standard physical performance measures (SPPB, gait speed, FSTS, 2-Minute Walk Test (2MWT), quadricep strength (QS), and GS) and on inertial measurement unit (IMU) measures of gait (stride length and gait speed), turns (turn duration, number of steps in turn, and turn velocity), sit-stand duration, and postural sway (root mean squared, pathlength, velocity, jerkiness). Intraclass correlation coefficients were assessed for reliability and differences between CKD and ESRD-D groups were assessed with paired t-tests. To assess the immediate effects of hemodialysis, standard physical performance measures (SPPB, gait speed, FSTS, 2MWT, QS, GS), the IMU measures previously described, and a fatigue numeric rating were collected immediately pre and post a hemodialysis session in 11 adults with ESRD-D. Paired t-tests were used to assess differences in physical performance pre-post dialysis and Pearson correlations were examined to assess the relationship between pre-post HD changes in physical performance, post-dialysis fatigue rating (PDF) and dialysis-related variables (Kt/V, pre-post HD weight change, # of months on HD, and intradialytic hemodynamic instability (HI)). Results. Fatigue was significantly associated with FSTS and gait speed and contributed to 2.1% and 3.1% of the variance in FSTS and gait speed, respectively. This relationship remained even after adjusting for covariates. Mobility disability was not associated with fatigue. Good-excellent test-retest reliability was demonstrated in the following standard physical performance measures: SPPB (ICC = .91), FSTS (ICC = .95), gait speed (ICC = .89), 2MWT (ICC = .94), NSB (ICC = .81), QS (ICCright = .94 and ICCleft =.90), GS (ICC = .96). Good reliability was found for the following IMU measures: steps in turn (ICC=.75), FSTS sit-stand duration (ICC=.87), postural sway PATH (ICC=.77usual and .85narrow), and sway JERK (ICCnarrow=.70). No differences were found between groups on physical performance measures. Statistically significant differences from pre-post HD were found on quadricep strength dynamometry (t (10) = 3.35, p <.01). There were significant positive correlations between HI and post-dialysis fatigue (PDF) (r = 0.72), indicating that PDF was associated with increased HI. There was a significant positive correlation between FSTS and HI instability (r = 0.63) indicating that poorer performance on the FSTS was related to increased HI. Conclusions. This dissertation identified a relationship between fatigue and physical performance in those with CKD, a set of clinically reliable physical performance measures for use with CKD/ESRD-D, and evidence that strength may decline immediately following a hemodialysis session. Future research directions include detection of the direction of causal relationships between fatigue and physical performance, development of a psychometrically strong composite physical performance outcome measure for CKD/ESRD, and identification of pathophysiological mechanisms related to strength decline following dialysis.