Epidemiology of Chronic Kidney Disease in the Elderly
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/1.73m 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/1.73m was 13.7% and of CKD-EPI eGFR was 12.9%. After adjustment for several confounders, only those with an eGFR <45 mL/min/1.73m had significantly higher all-cause and cardiovascular mortality than those with an eGFR of 75–89 mL/min/1.73m whatever the equation. In the subsample men and women with an MDRD eGFR of 45–59 mL/min/1.73m, 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/1.73m/year.
Conclusions. Moderately decreased eGFR is more often associated with clinical markers in men than in women. In both sexes, eGFR <45 mL/min/1.73m 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.
Chronic kidney disease (CKD) as defined by the Kidney Disease Outcome Quality Initiative (K/DOQI) is increasingly recognized as a public health priority and targeted in prevention programmes. Routine reporting of estimated glomerular filtration rate (eGFR) has led to the identification of up to nearly half of the elderly as having CKD with increased referrals to nephrologists. Because CKD diagnosis in many of these subjects is based only on either microalbuminuria or moderately decreased eGFR (i.e. 30–59 mL/min/1.73m), controversy exists about its clinical relevance, especially given how little is known about normal kidney function level [18, 19] and the epidemiology of CKD in the elderly.
More information is needed about the prevalence of clinically significant kidney markers such as clinical proteinuria, resistant hypertension or anaemia in the older people. Data on eGFR change over time are also needed to better define rapid decline in this population. Moreover, although several studies have shown increased mortality risk with decreasing eGFR, others suggest that age attenuates these associations. Finally, use of a creatinine enzymatic assay and development of new equations improved eGFR assessment, but while the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation has shown to better categorize middle-aged individuals with respect to long-term outcomes compared with the Modification of Diet in Renal Disease (MDRD) study equation, distribution of eGFR values according to one another and risk implications in the oldest are unknown.
We therefore determined age- and sex-specific eGFR using both the MDRD and CKD-EPI equations in community-dwelling people aged 65 years and older participating in the Three-City (3C) cohort study and studied their relations to 6-year all-cause and cardiovascular mortality risks. In a subsample, we also assessed eGFR decline at 4 years and CKD markers.
Abstract and Introduction
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/1.73m 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/1.73m was 13.7% and of CKD-EPI eGFR was 12.9%. After adjustment for several confounders, only those with an eGFR <45 mL/min/1.73m had significantly higher all-cause and cardiovascular mortality than those with an eGFR of 75–89 mL/min/1.73m whatever the equation. In the subsample men and women with an MDRD eGFR of 45–59 mL/min/1.73m, 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/1.73m/year.
Conclusions. Moderately decreased eGFR is more often associated with clinical markers in men than in women. In both sexes, eGFR <45 mL/min/1.73m 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.
Introduction
Chronic kidney disease (CKD) as defined by the Kidney Disease Outcome Quality Initiative (K/DOQI) is increasingly recognized as a public health priority and targeted in prevention programmes. Routine reporting of estimated glomerular filtration rate (eGFR) has led to the identification of up to nearly half of the elderly as having CKD with increased referrals to nephrologists. Because CKD diagnosis in many of these subjects is based only on either microalbuminuria or moderately decreased eGFR (i.e. 30–59 mL/min/1.73m), controversy exists about its clinical relevance, especially given how little is known about normal kidney function level [18, 19] and the epidemiology of CKD in the elderly.
More information is needed about the prevalence of clinically significant kidney markers such as clinical proteinuria, resistant hypertension or anaemia in the older people. Data on eGFR change over time are also needed to better define rapid decline in this population. Moreover, although several studies have shown increased mortality risk with decreasing eGFR, others suggest that age attenuates these associations. Finally, use of a creatinine enzymatic assay and development of new equations improved eGFR assessment, but while the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation has shown to better categorize middle-aged individuals with respect to long-term outcomes compared with the Modification of Diet in Renal Disease (MDRD) study equation, distribution of eGFR values according to one another and risk implications in the oldest are unknown.
We therefore determined age- and sex-specific eGFR using both the MDRD and CKD-EPI equations in community-dwelling people aged 65 years and older participating in the Three-City (3C) cohort study and studied their relations to 6-year all-cause and cardiovascular mortality risks. In a subsample, we also assessed eGFR decline at 4 years and CKD markers.
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