| Hemoglobin variability and mortality: confounding by disease severity. | |
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MedLine Citation:
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PMID: 20801571 Owner: NLM Status: In-Data-Review |
Abstract/OtherAbstract:
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BACKGROUND: Substantial variability in hemoglobin levels has been associated with increased mortality risk in hemodialysis patients. Variability also has been associated with concurrent comorbid conditions and hospitalization. Adequate adjustment for confounding by disease severity is needed to estimate the association of hemoglobin level variability with mortality risk. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: Medicare hemodialysis patients in 3 groups: prevalent on July 1, 2006 (n = 133,246), prevalent on July 1, 1996 (n = 78,602), and incident between January 1, 2005, and June 30, 2006 (n = 24,999). PREDICTOR: Hemoglobin level variability estimated using the residual deviation around the linear trend in hemoglobin levels during a 6-month entry period. OUTCOME: Time to death. MEASUREMENTS: We fit Cox models of 1-year mortality with and without adjustment for disease severity (comorbid conditions, hospitalization days, and months with hemoglobin level <10 g/dL), measured concurrently with hemoglobin level variability. RESULTS: Disease severity was associated positively with hemoglobin level variability in all groups. Before adjustment for disease severity, HRs for hemoglobin level variability were 1.27 (95% CI, 1.24-1.31) per 1 g/dL for patients prevalent in 2006, 1.32 (95% CI, 1.27-1.38) for patients prevalent in 1996, and 1.08 (95% CI, 1.03-1.13) for patients incident in 2005-2006. After adjustment, HRs for hemoglobin level variability were 1.02 (95% CI, 0.99-1.05), 1.07 (95% CI, 1.03-1.12), and 1.01 (95% CI, 0.95-1.06), respectively. LIMITATIONS: We did not adjust for time-varying confounding of hemoglobin level; an inclusion requirement introduces potential selection bias; our findings may not apply to incident hemodialysis patients younger than 65 years; assessment of comorbid conditions from claims is subject to misclassification, with possible residual confounding attributable to comorbid conditions; this observational study cannot prove causality. CONCLUSIONS: After adjustment for concurrent disease severity, evidence supporting an association between hemoglobin level variability and mortality risk was weak and inconsistent. The clinical utility of hemoglobin level variability may be limited. |
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Authors:
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Eric D Weinhandl; Yi Peng; David T Gilbertson; Brian D Bradbury; Allan J Collins |
Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: American journal of kidney diseases : the official journal of the National Kidney Foundation Volume: 57 ISSN: 1523-6838 ISO Abbreviation: Am. J. Kidney Dis. Publication Date: 2011 Feb |
Date Detail:
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Created Date: 2011-01-21 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8110075 Medline TA: Am J Kidney Dis Country: United States |
Other Details:
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Languages: eng Pagination: 255-65 Citation Subset: IM |
Copyright Information:
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Copyright © 2011 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved. |
Affiliation:
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Chronic Disease Research Group, Minneapolis Medical Research Foundation, Minneapolis, MN. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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