Obesity and Change in Estimated GFR Among Older Adults

Background: The prevalence of chronic kidney disease is growing most rapidly among older adults; however, determinants of impaired kidney function in this population are not well understood. Obesity assessed in midlife has been associated with chronic kidney disease. Study Design: Cohort study. Setting & Participants: 4,295 participants in the community-based Cardiovascular Health Study, aged >= 65 years. Predictors: Body mass index, waist circumference, and fat mass measured using bioelectrical impedance. Outcome: Change in glomerular filtration rate (GFR) during 7 years of follow-up. Measurements: Longitudinal estimates of GFR calculated using the 4-variable Modification of Diet in Renal Disease (MDRD) Study equation. Results: Estimated GFR decreased by an average of 0.4 +/- 3.6 mL/min/1.73 m(2)/y, and rapid GFR loss (>3 mL/min/1.73 m(2)/y) occurred in 693 participants (16% ). Baseline body mass index, waist circumference, and fat mass were each associated with increased risk of rapid GFR loss: ORs, 1.19 (95% Cl, 1.09-1.30) per5 kg/m(2),1.25 (95% Cl, 1.16-1.36) per 12 cm, and 1.14 (95%CI, 1.05-1.24) per 10 kg after adjustment for age, sex, race, and smoking. The magnitude of increased risk was larger for participants with estimated GFR < 60 mL/min/1.73 m(2) at baseline (P for interaction < 0.05). Associations were substantially attenuated by further adjustment for diabetes, hypertension, and C-reactive protein level. Obesity measurements were not associated with change in GFR estimated using serum cystatin C level. Limitations: Few participants with advanced chronic kidney disease at baseline, no direct GFR measurements. Conclusion: Obesity may be a modifiable risk factor for the development and progression of kidney disease in older adults. Am J Kidney Dis 54:1043-1051. (C) 2009 by the National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.