Association between changes in quality of life and mortality in hemodialysis patients: results from the DOPPS

Abstract

Background: Cross-sectional health-related quality of life (HR-QOL) measures are associated with mortality in hemodialysis (HD) patients. The impact of changes in HR-QOL on outcomes remains unclear. We describe the association of prior changes in HR-QOL with subsequent mortality among HD patients.

Methods: A total of 13 784 patients in the Dialysis Outcomes and Practice Patterns Study had more than one measurement of HR-QOL. The impact of changes between two measurements of the physical (PCS) and mental (MCS) component summary scores of the SF-12 on mortality was estimated with Cox regression.

Results: Mean age was 62 years (standard deviation: 14 years); 59% were male and 32% diabetic. Median time between HR-QOL measurements was 12 months [interquartile range (IQR): 11, 14]. Median initial PCS and MCS scores were 37.5 (IQR: 29.4, 46.2) and 46.4 (IQR: 37.2, 54.9); median changes in PCS and MCS scores were -0.2 (IQR: -5.5, 4.7) and -0.1 (IQR: -6.8, 5.9), respectively. The adjusted hazard ratio (HR) for a 5-point decline in HR-QOL score was 1.09 [95% confidence interval (CI): 1.06-1.12] for PCS and 1.05 (95% CI: 1.03-1.08) for MCS. Adjusting for the second QOL score, the change was not associated with mortality: HR = 1.01 (95% CI: 0.98-1.05) for delta PCS and 1.01 (95% CI: 0.98-1.03) for delta MCS. Categorizing the first and second scores as predictors, only the second PCS or MCS score was associated with mortality.

Conclusions: In our study, only the most recent HR-QOL score was associated with mortality. Hence, the predictive power of a measurement of HR-QOL is not affected by changes in HR-QOL prior to that measurement; more frequent HR-QOL measurements are needed to improve the prediction of outcomes in HD. Further studies are needed to determine the optimal frequency and appropriate instrument to be used for serial measurements.

Keywords: Dialysis Outcomes Practice Patterns Study; hemodialysis; quality of life; survival.

FIGURE 1

Distribution of PCS and MCS by region. Higher scores indicate better QOL. Diamond symbol represents the mean. PCS and MCS, physical and mental component summary of the SF-12; HR-QOL, health-related quality of life; A/NZ, Australia/New Zealand.

FIGURE 2

Distribution of change in PCS and MCS, overall and by vintage. PCS and MCS, physical and mental component summary of the SF-12; HR-QOL, health-related quality of life.

FIGURE 3

Association between mortality and change in HR-QOL. A total of 13 784 patients and 1478 deaths (11%). Follow-up began after PQ2. Two separate models stratified by phase and country, adjusted for gender, black race, 13 comorbidities, baseline vascular access, age and vintage at PQ2, and BMI, albumin and hemoglobin at both PQ1 and PQ2. P-values correspond to testing change in HR-QOL as a continuous variable. PQ1, first patient questionnaire; PQ2, second patient questionnaire ∼1 year later; PCS and MCS, physical and mental component summary of the SF-12; HR-QOL, health-related quality of life; CI, confidence interval; BMI, body mass index.

FIGURE 4

Frequency of facility HR-QOL measurement by country. A total of 321 facilities responding to the DOPPS Phase 4 (2009–2011) UPS question: Is patient QOL routinely (at least once yearly) assessed? HR-QOL, health-related quality of life; DOPPS, Dialysis Outcomes and Practice Patterns Study; UPS, Unit Practice Survey; US, United States; A/NZ, Australia and New Zealand; Can, Canada; Spa, Spain; Bel, Belgium; Ger, Germany; Ita, Italy; UK, United Kingdom; Swe, Sweden; Fra, France; Jpn, Japan.