Epidemiology and prognostic significance of chronic kidney disease in the elderly--the Three-City prospective cohort study

Abstract

Background: Little is known about normal kidney function level and the prognostic significance of low estimated glomerular filtration rate (eGFR) in the elderly.

Methods: We determined age and sex distribution of eGFR with both the Modification of Diet in Renal Disease (MDRD) study and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in 8705 community-dwelling elderly aged ≥ 65 years and studied its relation to 6-year mortality. In a subsample of 1298 subjects examined at 4 years, we assessed annual eGFR decline and clinically relevant markers including microalbuminuria (3-30 mg/mmol creatinine) with diabetes, proteinuria ≥ 50 mg/mmol, haemoglobin <11 g/L or resistant hypertension despite three drugs.

Results: Median (interquartile range) MDRD eGFR was 78 (68-89) mL/min/1.73 m(2) in men and 74 (65-83) in women; there were 79 (68-87) and 77 (67-85) for CKD-EPI eGFR, respectively. Prevalence of MDRD eGFR <60 mL/min/1.73 m(2) was 13.7% and of CKD-EPI eGFR was 12.9%. After adjustment for several confounders, only those with an eGFR <45 mL/min/1.73 m(2) had significantly higher all-cause and cardiovascular mortality than those with an eGFR of 75-89 mL/min/1.73 m(2) whatever the equation. In the subsample men and women with an MDRD eGFR of 45-59 mL/min/1.73 m(2), 15 and 13% had at least one clinical marker and 15 and 3% had microalbuminuria without diabetes, respectively; these percentages were 41 and 21% and 23 and 10% in men and women with eGFR <45, respectively. Mean MDRD eGFR decline rate was steeper in men than in women, 1.75 versus 1.41 mL/min/1.73 m(2)/year.

Conclusions: Moderately decreased eGFR is more often associated with clinical markers in men than in women. In both sexes, eGFR <45 mL/min/1.73 m(2) is related to poor outcomes. The CKD-EPI and the MDRD equations provide very similar prevalence and long-term risk estimates in this elderly population.

Figure 1

Three-City Study flow chart

Figure 2. Prevalence of kidney damage markers according to eGFR level in the subsample

Microalbuminuria defined as an albumin:creatinine ratio ≥ 3 (30) and <30 (300) mg/mmol (mg/g) and clinical proteinuria as a protein:creatinine ratio ≥ 50 mg/mmol (≥500 mg/g). Resistant hypertension defined as a blood pressure ≥ 130/80 mmHg for those with either an eGFR<60 mL/min/1.73 m², diabetes, proteinuria ≥ 50 mg/mmol or albuminuria ≥ 30 mg/mmol, otherwise the threshold was 140/90 mmHg. Anemia defined as an hemoglobin <11 g/dL

Figure 3. Prevalence of CKD stages and distribution of isolated low eGFR, microalbuminuria without diabetes, and at least one clinically relevant marker by CKD stage and sex

Microalbuminuria defined as an albumin:creatinine ratio ≥ 3 (30) and <30 (300) mg/mmol (mg/g); clinically relevant markers include microalbuminuria with diabetes, clinical proteinuria defined as a protein:creatinine ratio ≥ 50 mg/mmol (≥500 mg/g), anaemia defined as an hemoglobin <11 g/dL, and resistant hypertension defined as a blood pressure ≥ 130/80 mmHg for those with either an eGFR<60 mL/min/1.73 m², diabetes, proteinuria ≥ 50 mg/mmol or albuminuria ≥ 30 mg/mmol, otherwise the threshold was 140/90 mmHg.