Obesity and change in estimated GFR among older adults

Abstract

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 >or= 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% CI, 1.09-1.30) per 5 kg/m(2), 1.25 (95% CI, 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.

Figure 1

Distribution of change in kidney function over follow-up. Change in glomrular filtration rate (GFR) is calculated from longitudinal measurements of serum creatinine using the 4-variable MDRD (Modification of Diet in Renal Disease) Study equation. Rapid renal function decline, defined as loss of estimated glomerular filtration rate exceeding 3 mL/min/1.73m²/year, occurred in 16% of participants and is shown with black bars.

Figure 2

Risk of rapid renal function decline, stratified by sex (women, open circles; men, filled squares) and adjusted for age, race, and smoking. Change in kidney function is calculated from longitudinal measurements of serum creatinine using the 4-variable MDRD (Modification of Diet in Renal Disease) Study equation. Rapid renal function decline is defined as loss of estimated glomerular filtration rate exceeding 3 mL/min/1.73m²/year.

Figure 3

Risk of rapid renal function decline, stratified by baseline estimated glomerular filtration rate (<60 mL/min/1.73m², filled diamonds; 60–89 mL/min/1.73m², filled triangles; ≥ 90 mL/min/1.73m², open triangles) and adjusted for age, race, and smoking. Change in kidney function is calculated from longitudinal measurements of serum creatinine using the 4-variable MDRD (Modification of Diet in Renal Disease) Study equation. Rapid renal function decline is defined as loss of estimated glomerular filtration rate exceeding 3 mL/min/1.73m²/year.

Figure 4

Risk of rapid renal function decline calculated from longitudinal measurements of serum cystatin C. Analyses are stratified by baseline estimated glomerular filtration rate (<60 mL/min/1.73m², filled diamonds; 60–89 mL/min/1.73m², filled triangles; ≥ 90 mL/min/1.73m², open triangles) and adjusted for age, race, and smoking. Rapid renal function decline is defined as loss of estimated glomerular filtration rate exceeding 3 mL/min/1.73m²/year.