Self-Motivation Is Associated With Phosphorus Control in End-Stage Renal Disease.
OBJECTIVE
Hyperphosphatemia is common in end-stage renal disease and associates with mortality. Phosphate binders reduce serum phosphorus levels; however, adherence is often poor. This pilot study aims to assess patients' self-motivation to adhere to phosphate binders, its association with phosphorus control, and potential differences by race.


METHODS
Cross sectional design. Subjects were enrolled from one academic medical center dialysis practice from July to November 2012. Self-motivation to adhere to phosphate binders was assessed with the autonomous regulation (AR) scale (range: 1-7) and self-reported medication adherence with the Morisky Medication Adherence Scale. Linear regression models adjusting for age, sex, health literacy, and medication adherence were applied to determine associations with serum phosphorus level, including any evidence of interaction by race.


RESULTS
Among 100 participants, mean age was 51 years (±15 years), 53% were male, 72% were non-white, 89% received hemodialysis, and mean serum phosphorus level was 5.7 ± 1.6 mg/dL. More than half (57%) reported the maximum AR score (7). Higher AR scores were noted in those reporting better health overall (P = .001) and those with higher health literacy (P = .01). AR score correlated with better medication adherence (r = 0.22; P = .02), and medication adherence was negatively associated with serum phosphorus (r = -0.40; P < .001). In subgroup analysis among non-whites, higher AR scores correlated with lower serum phosphorus (high vs lower AR score: 5.55 [1.5] vs 6.96 [2.2]; P = .01). Associations between AR score (β 95% confidence interval: -0.37 [-0.73 to -0.01]; P = .04), medication adherence (β 95% confidence interval: -0.25 [-0.42 to -0.07]; P = .01), and serum phosphorus persisted in adjusted analyses.


CONCLUSIONS
Self-motivation was associated with phosphate binder adherence and phosphorus control, and this differed by race. Additional research is needed to determine if personalized, culturally sensitive strategies to understand and overcome motivational barriers may optimize mineral bone health in end-stage renal disease.
Division of Nephrology and Hypertension, Vanderbilt University, Nashville, Tennessee; Vanderbilt Center for Kidney Disease, Nashville, Tennessee.
Ebele M
EM
Umeukeje
School of Social Work, University of Minnesota, Saint Paul, Minnesota.
Joseph R
JR
Merighi
College of Social Work, University of South Carolina, Columbia, South Carolina.
Teri
T
Browne
School of Medicine, University of Washington, Seattle, Washington.
Jacquelyn N
JN
Victoroff
Division of Nephrology and Hypertension, Henry Ford Hospital, Detroit, Michigan.
Kausik
K
Umanath
Division of Nephrology and Hypertension, Vanderbilt University, Nashville, Tennessee; Vanderbilt Center for Kidney Disease, Nashville, Tennessee.
Julia B
JB
Lewis
Division of Nephrology and Hypertension, Vanderbilt University, Nashville, Tennessee; Vanderbilt Center for Kidney Disease, Nashville, Tennessee.
T Alp
TA
Ikizler
Vanderbilt University School of Nursing, Nashville, Tennessee.
Kenneth A
KA
Wallston
Division of Nephrology and Hypertension, Vanderbilt University, Nashville, Tennessee; Vanderbilt Center for Kidney Disease, Nashville, Tennessee. Electronic address: kerri.cavanaugh@vanderbilt.edu.
Kerri
K
Cavanaugh
D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D054559:Hyperphosphatemia / Q000097:blood*; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy; D016014:Linear Models; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D009042:Motivation; D010758:Phosphorus / Q000097:blood*; D010865:Pilot Projects; D006435:Renal Dialysis; D057566:Self Report
D010758:Phosphorus