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Abstract: TH-PO1101

The Relationship Between Body Mass Index (BMI) and Outcomes in Health and CKD

Session Information

Category: CKD (Non-Dialysis)

  • 1901 CKD (Non-Dialysis): Epidemiology, Risk Factors, and Prevention

Authors

  • Raimann, Jochen G., Renal Research Institute, New York, New York, United States
  • Kotanko, Peter, Renal Research Institute, New York, New York, United States
  • Waldron, Levi D., Waldron Lab, CUNY Graduate School of Public Health and Health Policy, New York, New York, United States
Background

In the general population the relationship between BMI and mortality is U-shaped, while in the hemodialysis (CKD 5D) population lower risk at higher BMI was observed. Pathophysiologic explanations exist, but disease may also act as a statistical collider creating a “selection bias by death”. We studied the relationship across CKD stages and in various subpopulations.

Methods

We studied healthy subjects, CKD patients at various stages (NHANES 1999 to 2010), and CKD5D patients dialyzing in Renal Research Institute (RRI) clinics. We constructed Cox proportional hazard models and depicted hazard ratios over a wide BMI range using spline functions and evaluated differences between subsets stratified by age (</>= 55 years), gender, race, and ethnicity. We also constructed polynomial models to test for an interaction between CKD stage and BMI in the Cox models. Akaike Information Criterion (AIC) was computed to determine the most accurate model.

Results

We studied 21569 healthy subjects, 8621 CKD stage 2 patients, 2507 CKD stage 3-5 patients, and 4351 CKD5D patients. We found consistently an inverse association between BMI and mortality in CKD5D patients and variations in the other subsets. While the interaction between CKD stage and BMI were significant in all constructed models, the final model with the lowest AIC value include only an interaction between CKD5D and BMI.

Conclusion

Our data show a consistent U-shaped relationship between BMI and all-cause mortality in the general population, but an “obesity paradox” in CKD5D. While the biological reasons are elusive, the consistency of the observation across all analyses suggests a pathophysiological relationship in concert with CKD acting as a statistical collider.

Spline function of hazard ratio of all-cause mortality over a 3-year follow-up period as a function of body mass index (BMI).