Original investigation
Dialysis therapy
Association of Morbid Obesity and Weight Change Over Time With Cardiovascular Survival in Hemodialysis Population

https://doi.org/10.1053/j.ajkd.2005.05.020Get rights and content

Background: In maintenance hemodialysis (MHD) outpatients, a reverse epidemiology is described, ie, baseline obesity appears paradoxically associated with improved survival. However, the association between changes in weight over time and prospective mortality is not known. Methods: Using time-dependent Cox models and adjusting for changes in laboratory values over time, the relation of quarterly-varying 3-month averaged body mass index (BMI) to all-cause and cardiovascular mortality was examined in a 2-year cohort of 54,535 MHD patients from virtually all DaVita dialysis clinics in the United States. Results: Patients, aged 61.7 ± 15.5 (SD) years, included 54% men and 45% with diabetes. Time-dependent unadjusted and multivariate-adjusted models, based on quarterly-averaged BMI controlled for case-mix and available time-varying laboratory surrogates of nutritional status, were calculated in 11 categories of BMI. Obesity, including morbid obesity, was associated with better survival and reduced cardiovascular death, even after accounting for changes in BMI and laboratory values over time. Survival advantages of obesity were maintained for dichotomized BMI cutoff values of 25, 30, and 35 kg/m2 across almost all strata of age, race, sex, dialysis dose, protein intake, and serum albumin level. Examining the regression slope of change in weight over time, progressively worsening weight loss was associated with poor survival, whereas weight gain showed a tendency toward decreased cardiovascular death. Conclusion: Weight gain and both baseline and time-varying obesity may be associated with reduced cardiovascular mortality in MHD patients independent of laboratory surrogates of nutritional status and their changes over time. Morbidly obese patients have the lowest mortality. Clinical trials need to verify these observational findings.

Section snippets

Database Creation

Database creation has been described elsewhere.7 In summary, the data warehouse of DaVita, Inc, the then second largest dialysis care provider in the United States, had information on approximately 40,000 patients at any given time and was accessed to obtain all relevant data between July 1, 2001, and June 30, 2003. All repeated measures of every relevant variable for each patient within a given quarter (13-week interval) were averaged to obtain 1 quarterly mean value for that variable. Hence,

Results

The original 2-year national database for all MHD patients included 69,819 subjects. After implementing the mentioned selection criteria, including deleting patients who were not maintained beyond 3 months of MHD therapy or who had inadequate or overtly missing data, the resulting cohort included 58,058 MHD patients, of whom 37,049 patients (64%) originated from the q1 data set, and the rest, from the subsequent quarters (q2 through q8). Table 1 lists baseline demographic, clinical, and

Discussion

In a national database cohort that included all eligible MHD patients of a major dialysis care provider with uniform patient management practices and standardized laboratory values, all measured in 1 laboratory, we found that obesity, including morbid obesity, is associated with improved survival and reduced cardiovascular death. These associations were independent of changes in BMI during the 2-year study period and held even after adjustment for time-varying laboratory surrogates of

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  • Cited by (0)

    Originally published online as doi:10.1053/j.ajkd.2005.05.020 on July 15, 2005.

    Supported in part by a Young Investigator Award from the National Kidney Foundation and grant no. DK61162 (K.K.-Z.) from the National Institute of Diabetes, and Digestive and Kidney Diseases. C.J.M. is an employee of DaVita, Inc.

    1

    K.K.-Z. contributed to the design of the study, collation and analysis of data, and writing of the manuscript and its revisions

    2

    J.D.K. contributed to the design and analysis of the study and provided advice and consultation on the writing of the manuscript and final review and approval

    3

    R.D.K. contributed to analysis of the data and reviewed and approved the final manuscript

    4

    C.J.M. contributed to the design of the study, provision of data, and final review and approval of the manuscript

    5

    C.S.S. contributed to analysis of the data and reviewed and approved the final manuscript

    6

    D.W.G. contributed to the design of the study and analysis of data and reviewed and approved the final manuscript

    7

    S.G. contributed to the design of the study, provided advice and consultation on the study design, analysis, and writing of the manuscript, and final review and approval

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