Progression of kidney dysfunction in the community-dwelling elderly

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

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.

Nocturnal hypoxia and loss of kidney function

Background

Although obstructive sleep apnea (OSA) is more common in patients with kidney disease, whether nocturnal hypoxia affects kidney function is unknown.

Methods

We studied all adult subjects referred for diagnostic testing of sleep apnea between July 2005 and December 31 2007 who had serial measurement of their kidney function. Nocturnal hypoxia was defined as oxygen saturation (SaO2) below 90% for ≥12% of the nocturnal monitoring time. The primary outcome, accelerated loss of kidney function, was defined as a decline in estimated glomerular filtration rate (eGFR) ≥4 ml/min/1.73 m² per year.

Results

858 participants were included and followed for a mean study period of 2.1 years. Overall 374 (44%) had nocturnal hypoxia, and 49 (5.7%) had accelerated loss of kidney function. Compared to controls without hypoxia, patients with nocturnal hypoxia had a significant increase in the adjusted risk of accelerated kidney function loss (odds ratio (OR) 2.89, 95% confidence interval [CI] 1.25, 6.67).

Conclusion

Nocturnal hypoxia was independently associated with an increased risk of accelerated kidney function loss. Further studies are required to determine whether treatment and correction of nocturnal hypoxia reduces loss of kidney function.

Modification of outcomes after acute kidney injury by the presence of CKD

BACKGROUND

Acute kidney injury (AKI) in hospitalized patients is associated with poor outcomes; however, it is unclear how relationships between AKI and clinical outcomes vary with baseline kidney function.

STUDY DESIGN

Population-based cohort.

SETTING & PARTICIPANTS

Adults in Alberta, Canada, who were hospitalized between January 1, 2003, and December 31, 2006, with at least 1 serum creatinine measurement during hospitalization and 1 outpatient creatinine measurement within 6 months preceding admission.

PREDICTOR

Baseline kidney function, defined as mean estimated glomerular filtration rate (eGFR) of all outpatient creatinine measurements within 6 months before the index hospitalization, and AKI, defined using consensus criteria.

OUTCOMES

Death during the index hospitalization and death or end-stage renal disease (ESRD) after hospitalization.

RESULTS

AKI occurred in 18.3% of the 43,008 hospitalized patients in the cohort. Risk of AKI increased with decreasing eGFR (8.9% with eGFR ≥60 mL/min/1.73 m(2) vs 68.9% with eGFR <30 mL/min/1.73 m(2)). In multivariable Cox models, AKI of any severity was associated with death during the index hospitalization across all levels of eGFR, with an HR of 2.99 (95% CI, 2.59-3.44) in patients who had the least severe AKI across all eGFR strata up to an HR of 10.62 (95% CI, 8.78-12.82) in patients with baseline eGFR >60 mL/min/1.73 m(2) and the most severe AKI. The risk of death or ESRD decreased after discharge, with the highest risk of ESRD after AKI noted in patients with eGFR <30 mL/min/1.73 m(2) (17.0% in the AKI group vs 5.6% in the non-AKI group; P < 0.01).

LIMITATIONS

The study cohort is restricted to patients who had outpatient serum creatinine values available.

CONCLUSIONS

AKI of any severity increases the risk of death both during hospitalization and after discharge. Although the risk of developing ESRD after AKI is greatest in patients with baseline eGFR <30 mL/min/1.73 m(2), this is exceeded by the risk of death.

Mitochondrial damage-induced impairment of angiogenesis in the aging rat kidney

Decreased expression of vascular endothelial growth factor (VEGF) in the renal tubules is thought to cause progressive loss of the renal microvasculature with age. Mitochondrial dysfunction may be a principal phenomenon underlying the process of aging. The relation between VEGF expression and mitochondrial dysfunction in aging is not fully understood. We hypothesized that mitochondrial dysfunction blocks VEGF expression and contributes to impaired angiogenesis in the aging kidney. The aim of this study was to assess the role of mitochondria in VEGF expression in the aging rat kidney. We evaluated the accumulation of 8-hydroxy-2'-deoxyguanosine in mitochondrial DNA, as well as mitochondrial dysfunction, as assessed by electron microscopy of mitochondrial structure and histochemical staining for respiratory chain complex IV, in aging rat kidney. An increase in hypoxic area and a decrease in peritubular capillaries were detected in the cortex of aging rat kidneys; however, upregulation of VEGF expression was not observed. The expression of VEGF in proximal tubular epithelial cells in response to hypoxia was suppressed by the mitochondrial electron transfer inhibitor myxothiazol. Mitochondrial DNA-deficient cells also failed to upregulate VEGF expression under hypoxic conditions. These results indicate that impairment of VEGF upregulation, possibly as a result of mitochondrial dysfunction, contributes to impaired angiogenesis, which in turn leads to renal injury in the aging rat kidney.

The epidemic of chronic kidney disease: looking at ageing and cardiovascular disease through kidney-shaped lenses

In recent years, a 'silent' chronic kidney disease (CKD) epidemic has been proposed by many authors. The 'outbreak' is because of the inclusion of a large proportion of the elderly population within stage 3 CKD according to the Kidney Disease Outcomes Quality Initiative staging system. Unfortunately, this does not take into account the fact that renal function normally declines with age; in addition, the Modification of Diet in Renal Disease formula used to calculate glomerular filtration rate underestimates renal function in the elderly. Because population preventive strategies need a precise definition of the target for screening, a more accurate tool to detect CKD in the general population is required. Considerable interest in CKD has been generated by the evidence that predialysis CKD is associated with increased risk of cardiovascular disease (CVD). Such an association per se does not imply that CKD is a causal determinant of CVD. As CKD has been detected particularly in elderly individuals, it is tempting to speculate that an association may exist between age and cardiovascular outcomes in patients with CKD. Furthermore, the definition of CKD is a nosographic simplification that includes diseases with different causes and pathogenetic mechanisms. The aetiologies of renal diseases can affect cardiovascular outcomes, and the two major causes of end-stage renal disease, diabetes mellitus and hypertension, indeed do so. These findings point to a need for a better definition of CKD to optimize the allocation of healthcare resources and to clarify the nature of the association between CKD and CVD.

Electrolytes in the aging

The elderly population in the United States continues to grow and is expected to double by 2050. With aging, there are degenerative changes in many organs and the kidney is no exception. After 40 years of age, there is an increase in cortical glomerulosclerosis and a decline in both glomerular filtration rate and renal plasma flow. These changes may be associated with an inability to excrete a concentrated or a dilute urine, ammonium, sodium, or potassium. Hypernatremia and hyponatremia are the most common electrolyte abnormalities found in the elderly and both are associated with a high mortality. Under normal conditions, the elderly are able to maintain water and electrolyte balance, but this may be jeopardized by an illness, a decline in cognitive ability, and with certain medications. Therefore, it is important to be aware of the potential electrolyte abnormalities in the elderly that can arise under these various conditions to prevent adverse outcomes.

Chronic kidney disease and end-stage renal disease in the elderly population: current prevalence, future projections, and clinical significance

The world's population is aging, with the number of older adults projected to increase dramatically over the next 2 decades. This trend poses major challenges to health care systems, reflecting the greater health care use and more comorbid conditions among elderly adults. Chronic kidney disease (CKD) is a substantial concern in the elderly population, with both an increasing incidence of treated kidney failure with dialysis as well as a high prevalence of earlier stages of CKD. Given the high burden of risk factors for CKD, the high prevalence of CKD in the elderly population is not surprising, with the rise in obesity, diabetes, and hypertension in middle-aged adults likely foreshadowing further increases in CKD prevalence among the elderly population. It is now commonly agreed that the presence of CKD identifies a higher risk state in the elderly population, with increased risk for multiple adverse outcomes, including kidney failure, cardiovascular disease, cognitive impairment, and death. Accordingly, CKD in older adults is worthy of attention by both health care providers and patients, with the presence of a reduced glomerular filtration rate or albuminuria in the elderly potentially informing therapeutic and diagnostic decisions for these individuals.

Effect of kidney disease on acute coronary syndrome

Chronic kidney disease (CKD) is highly prevalent worldwide and is associated with an increased risk for adverse outcomes in patients hospitalized with acute coronary syndrome (ACS). In studies including thousands of patients admitted with myocardial infarction, CKD consistently determines a poorer prognosis for ACS patients. In contrast with CKD, information about the effect of acute kidney injury (AKI) on clinical outcomes after ACS is limited. Most data come from retrospective registry databank studies of nonconsecutive patients with a significant number of patients excluded from analyses. There are no prospective studies designed to determine whether AKI strictly diagnosed by the new the Acute Kidney Injury Network (AKIN) or RIFLE (Risk, Injury, Failure, Loss, and End-stage kidney disease) criteria is a risk factor for death after ACS, and there are no data comparing the RIFLE and AKIN criteria for AKI diagnosis after myocardial infarction. This article reviews the most important data on CKD and ACS and the available data on AKI and ACS. The importance of obtaining an early serum creatinine level after admission for ACS and the importance of renal function monitoring during hospitalization are stressed.

Slowing the progression of chronic kidney disease

Progression of chronic kidney disease can be slowed by careful management of risk factors. The most effective treatments are aggressive blood pressure control, renin-angiotensin system inhibition in proteinuric patients and tight glycaemic control in diabetics. Patients should be educated to avoid nephrotoxins and maintain a healthy lifestyle.

Longitudinal measurements of renal function

Cross-sectional studies have long suggested that renal function declines with age among adults. However, there are limited longitudinal studies with data on within-individual changes in renal function over time. The Baltimore Longitudinal Study of Aging provided some of the first data on within-person changes in renal function over time. In a subsample of this cohort without renal disease, followed up to 23 years, creatinine clearance declined by a mean of -0.75 mL/min/1.73 m(2) per year. Interestingly, 35% of individuals in this study did not experience a decline in renal function. Similar findings from longitudinal studies of patients with established chronic kidney disease have been reported. Among 1,094 participants with up to 10 years of follow-up evaluation in the African-American Study of Kidney Disease, the mean annual rates of decline in estimated glomerular filtration rate were -2.11 mL/min/1.73 m(2) and -1.50 mL/min/1.73 m(2) during the trial and observational phases, respectively. Of participants with at least 7 years of follow-up evaluation, 33.5% experienced a mean annual decline in estimated glomerular filtration rate of less than -1 mL/min/1.73 m(2). More studies are needed to better define longitudinal changes in renal function. Such data will provide important information for guiding treatment choices for patients, research endeavors, and health policy.

Sexual dimorphism, the aging kidney, and involvement of nitric oxide deficiency

Females develop less age-dependent loss of renal function, in part because of cardiorenal protective effects of estrogens. The low androgen level in women also may be protective, although the animal and clinical data are controversial. Both estrogen and androgens act through multiple mechanisms, sometimes beneficial, sometimes damaging, which makes it difficult to predict the impact of hormone replacement therapy in an aging population. Nitric oxide (NO) deficiency contributes to age-dependent cardiovascular risk and kidney damage in animal models. The increased oxidative stress of aging impacts at multiple sites in the NO biosynthetic pathway to decrease NO production/action. Endothelial dysfunction develops with aging and is delayed in women, in association with a delayed increase in asymmetric dimethylarginine. Animal data suggest that the aging kidney develops NO deficiency because of changes in the neuronal NO synthase. Relative preservation of NO production in females contributes to the better cardiovascular and renal responses to aging.

Geriatric nephrology: responding to a growing challenge

Changing demographics of the global population predict that the number of people age 65 years or greater will triple over the coming decades. Because the incidence and prevalence of kidney disease increase with advancing age, nephrologists will be increasingly confronted with a population of patients who are elderly and have a large number of comorbid conditions requiring ongoing care. Furthermore, it is increasingly understood that aging leads to its own unique aspects of nephrologic diagnosis and treatment. Although it is known that elderly patients constitute a group with special needs and present unique challenges to the nephrologist, traditional nephrology fellowship training has not included a focus on the geriatric population. In response to this need for greater education and awareness, the American Society of Nephrology has initiated a program of educational activities in geriatric nephrology and has chartered a specific advisory council. The priority being given to geriatric nephrology is a hopeful sign that issues such as treatment options, the efficacy of treatments, and their effect on quality of life for the elderly patient with kidney disease will be improved in the coming years.

Relationship between renal dysfunction and severity of coronary artery disease in Japanese patients

BACKGROUND

The relationship between renal dysfunction and the severity of coronary artery disease (CAD) was examined.

METHODS AND RESULTS

The severity of CAD in 572 patients was graded according to the number of stenotic coronary arteries, and the estimated glomerular filtration rate (eGFR) was monitored for 3 years. Patients were stratified into 3 eGFR groups: normal (>75 ml x min(-1) x 1.73 m(-2)), mild reduction (60-75) and chronic kidney disease (CKD: <60). There were 161 patients in the CKD group. The average number of stenotic coronary arteries was larger in the CKD group than in the other groups (normal vs mild reduction vs CKD =1.35+/-0.07 (SE) vs 1.22+/-0.08 vs 1.69+/-0.08 vessel disease (VD), P<0.001). During the 3-year follow-up, the renal function of 13.8% of the patients worsened. Those who showed more deterioration of eGFR had more severe CAD than those who did not (1.20+/-0.06 vs 1.61+/-0.06 VD, P<0.001). Multivariate analysis revealed that the severity of CAD was independently and significantly associated with the deterioration of eGFR.

CONCLUSIONS

Patients with CKD had more severe CAD, which may explain the high rate of cardiovascular events in these patients. Moreover, the prognosis of renal function was poor in patients with severe CAD, and CAD was found to be an independent risk factor for worsening of renal dysfunction.

Clinical presentation of renal failure in the aged: chronic renal failure

Chronic kidney disease is increasingly being recognized in elderly individuals across the world. An understanding of the methods used to estimate or to measure kidney function, the likelihood and factors associated with progressive decline in renal function, and the clinical syndromes associated with poor renal function are key topics for individuals working across many medical disciplines. This review addresses some of the important aspects of chronic kidney disease, and summarizes some of the clinical and laboratory features associated with progressive disease.

Adverse drug reactions and impaired renal function in elderly patients admitted to the emergency department: a retrospective study

BACKGROUND

Adverse drug reactions (ADRs) are common in elderly patients. There are various reasons for this, including age- and disease-related alterations in pharmacokinetics and pharmacodynamics as well as the common practice of polypharmacy. The decline in renal function in elderly patients may also predispose them to pharmacological ADRs (type A, augmented). Patients receiving home healthcare may be at even higher risk.

OBJECTIVES

To study ADRs as a cause of acute hospital admissions in a defined cohort of elderly patients (aged >or=65 years) registered to receive home healthcare services, with special reference to impaired renal function as a possible risk factor.

METHODS

This was a retrospective study of 154 elderly patients aged >or=65 years admitted to the emergency department of a university hospital in Stockholm, Sweden, in October-November 2002. Estimated creatinine clearance (eCL(CR)) was calculated from the Cockcroft-Gault formula, and estimated glomerular filtration rate (eGFR) by the Modification of Diet in Renal Disease (MDRD) equation. ADRs were defined according to WHO criteria. All medications administered to patients at admission and at discharge were collated. These and other data were collected from computerized hospital records.

RESULTS

ADRs were judged to contribute to or be the primary cause of hospitalization in 22 patients, i.e. 14% of 154 patients registered to receive home healthcare. Eleven of the 22 patients were women. All but one ADR were type A. Excessive doses or drugs unsuitable in renal insufficiency were present in seven patients in the ADR group compared with only four patients in the group without ADRs (p = 0.0001). Patients with ADRs did not differ significantly from those without ADRs in relation to age, plasma creatinine, eCL(CR), weight or number of drugs prescribed at admission. However, women with ADRs were significantly older than women without ADRs (mean +/- SD age 88.8 +/- 5.7 years vs 82.5 +/- 8.0 years, respectively; p = 0.014) and had significantly lower mean +/- SD eCL(CR) values (25.5 +/- 10.8 and 37.1 +/- 17.1 mL/min, respectively; p = 0.035). Median MDRD eGFR was significantly higher than median eCL(CR) (59 [range 6-172] mL/min/1.73 m2 vs 38 [range 5-117] mL/min, respectively; p = 0.0001).

CONCLUSIONS

In elderly patients registered to receive home healthcare, 14% of hospital admissions were primarily caused by ADRs. One-third of these ADRs were related to impaired renal function, generally in very old women. These ADRs may be avoided by close monitoring of renal function and adjustments to pharmacotherapy (drug selection and dose), particularly in very elderly women.

Interaction of aging and chronic kidney disease

Our goals in this review are to describe what is known about the prevalence and clinical implications of non-dialysis-dependent chronic kidney disease in the elderly and to discuss some of the most common challenges to managing older patients with chronic kidney disease.

Analysis of multidisciplinary care models and interface with primary care in management of chronic kidney disease

Public policy efforts and education have led to an increased appreciation of the prevalence of chronic kidney disease (CKD) in general outpatient populations. The complexity of the care of individuals with established CKD has led to the development of multidisciplinary care models, which have been shown to improve the clinical outcomes of those with CKD. The interface between specialty and primary care in various systems remains necessary and desired, albeit a continuing challenge. This overview reviews various models of specialty care for CKD patients, including those that emphasize multidisciplinary team approaches, and highlight the essential role(s) of primary care physicians. Importantly, there is a need for improved definition of CKD populations and individuals, review and refinement of proposed care pathways, and the need to define essential elements of care for the patient. Models of care often are not subject to the same rigor that other interventions applied to this population are; nonetheless, we offer here a framework for establishing and evaluating care models for the CKD populations at various stages of disease and with various comorbidities.

Evolution of renal function in patients treated with antiangiogenics after nephrectomy for renal cell carcinoma

PURPOSE

Side effects of antiangiogenic agents are moderate compared with other therapies. The most frequent adverse events are of a renovascular origin and manifest as hypertension (HTN) and thrombotic microangiopathy. To date, data are scanty on the renal tolerance of such drugs regarding renal function as itself, i.e., glomerular filtration rate (GFR). We report on the evolution of GFR in patients receiving antiangiogenic therapy after unilateral nephrectomy for kidney cancer.

PATIENTS AND METHODS

Data from 73 patients followed in our oncology department for kidney cancer, who had undergone unilateral nephrectomy, and received any antiangiogenic therapy were reviewed. Their GFR was calculated using the aMDRD formula.

RESULTS

All patients showed a declining renal function over time (-1.23 and -2.51 mL/min/1.73 m(2) using the slope of the curve or the difference between GFR at baseline and that at the end of treatment, respectively). Among them, patients who were recorded as having HTN before initiation of antiangiogenic therapy showed a higher decrease in their GFR of -13.28 and -12.06 mL/min/1.73 m(2).

CONCLUSION

We recommend that blood pressure should be measured closely in those patients before initiation of antiangiogenic therapy. When HTN is diagnosed, it should be treated and renal function should be monitored since those patients may be at risk for rapidly decreasing renal function under therapy.

Incident chronic kidney disease and the rate of kidney function decline in individuals with hypertension

Background. Little is known about the decline of kidney function in patients with normal kidney function at baseline. Our objectives were to (i) identify predictors of incident chronic kidney disease (CKD) and (ii) to estimate rate of decline in kidney function.

Methods. The study used a retrospective cohort of adult patients in a hypertension registry in an inner-city health care delivery system in Denver, Colorado. The primary outcome was development of incident CKD, and the secondary outcome was rate of change of estimated glomerular filtration rate (eGFR) over time.

Results. After a mean follow-up of 45 months, 429 (4.1%) of 10 420 patients with hypertension developed CKD. In multivariate models, factors that independently predicted incident CKD were baseline age [odds ratio (OR) 1.13 per 10 years, 95% confidence interval (CI), 1.03–1.24], baseline eGFR (OR 0.69 per 10 units, 95% CI 0.65–0.73), diabetes (OR 3.66, 95% CI 2.97–4.51) and vascular disease (OR 1.67, 95% CI 1.32–2.10). We found no independent association between age, gender or race/ethnicity and eGFR slope. In patients who did not have diabetes or vascular disease, eGFR declined at 1.5 mL/min/1.73 m² per year. Diabetes at baseline was associated with an additional decline of 1.38 mL/min/1.73 m².

Conclusions. Diabetes was the strongest predictor of both incident CKD as well as eGFR slope. Rates of incident CKD or in decline of kidney function did not differ by race or ethnicity in this cohort.

Overview of the Alberta Kidney Disease Network

Background

The Alberta Kidney Disease Network is a collaborative nephrology research organization based on a central repository of laboratory and administrative data from the Canadian province of Alberta.

Description

The laboratory data within the Alberta Kidney Disease Network can be used to define patient populations, such as individuals with chronic kidney disease (using serum creatinine measurements to estimate kidney function) or anemia (using hemoglobin measurements). The administrative data within the Alberta Kidney Disease Network can also be used to define cohorts with common medical conditions such as hypertension and diabetes. Linkage of data sources permits assessment of socio-demographic information, clinical variables including comorbidity, as well as ascertainment of relevant outcomes such as health service encounters and events, the occurrence of new specified clinical outcomes and mortality.

Conclusion

The unique ability to combine laboratory and administrative data for a large geographically defined population provides a rich data source not only for research purposes but for policy development and to guide the delivery of health care. This research model based on computerized laboratory data could serve as a prototype for the study of other chronic conditions.

[Renal function evaluation methods in the elderly: reliability and clinical implications]

Chronic renal disease (CRD) is found in a third of the Spanish population aged more than 65 years old. Detection and early treatment would increase survival and help to reduce associated cardiovascular morbidity and mortality as well as the risk of pharmacological iatrogeny. Determination of the glomerular filtration rate has traditionally been considered the best parameter for renal function evaluation, which should not be based exclusively on serum creatinine concentration or creatinine clearance. The application of predictive equations is useful in the diagnosis, classification and outpatient management of patients with CRD. Most studies performed in the elderly have found that the Modification of Diet in Renal Disease (MDRD-4) has greater precision and accuracy than the Cockcroft-Gault formula, and is considered the nomogram of choice in this age group. The Cockcroft-Gault formula can be used when rapid estimation of renal function or drug adjustments are required, so long as the limitations of this method are taken into account.

Survival of patients from South Asian and Black populations starting renal replacement therapy in England and Wales

Background. South Asian and Black ethnic minorities in the UK have higher rates of acceptance onto renal replacement therapy (RRT) than Caucasians. Registry studies in the USA and Canada show better survival; there are few data in the UK.

Methods. Renal Association UK Renal Registry data were used to compare the characteristics and survival of patients starting RRT from both groups with those of Caucasians, using incident cases accepted between 1997 and 2006. Survival was analysed by multivariate Cox's proportional hazards regression split by haemodialysis and peritoneal dialysis (PD) due to non-proportionality, and without censoring at transplantation.

Results. A total of 2495 (8.2%) were South Asian and 1218 (4.0%) were Black. They were younger and had more diabetic nephropathy. The age-adjusted prevalence of vascular co-morbidity was higher in South Asians and lower in Blacks; other co-morbidities were generally common in Caucasians. Late referral did not differ. They were less likely to receive a transplant or to start PD. South Asians and Blacks had significantly better survival than Caucasians both from RRT start to Day 90 and after Day 90, and for those on HD or PD at Day 90. Fully adjusted hazard ratios after Day 90 on haemodialysis were 0.70 (0.55–0.89) for South Asians and 0.56 (0.41–0.75) for Blacks.

Conclusion. South Asian and Black minorities have better survival on dialysis. An understanding of the mechanisms may provide general insights for all patients on RRT.

Sexual dimorphism in the aging kidney: differences in the nitric oxide system

Females-both rats and women-are substantially protected against the age-dependent decrease in renal function that occurs in males of the species. In part, this finding reflects the cardioprotective and renoprotective effects of estrogens, but estrogen has multiple actions, not all of which are beneficial. In addition, the low androgen level in women might be protective against a decline in renal function, but animal and clinical data on possible adverse effects of androgens are controversial. Androgens also have multiple actions, one of which-aromatization to estrogen-is likely to be protective. Sex steroids clearly have many complex actions, which explains the conflicting information on their relative benefits and dangers. Endothelial nitric oxide (NO) deficiency contributes importantly to cardiovascular risk and intrarenal NO deficiency is clearly linked to chronic kidney disease progression in animal models. Endothelial dysfunction develops with increasing age but is delayed in females, correlating with a delayed rise in asymmetric dimethylarginine level. There is no clear link between aging and arginine (the NO synthase substrate) deficiency. Animal data suggest that the aging kidney develops NO deficiency as a result of changes in neuronal NO synthase. The increased oxidative stress that occurs with aging affects multiple stages of the NO biosynthetic pathway and results in decreased production and/or action of NO. NO production is better preserved in females than in males, partly as a result of the actions of estrogens.

Rate of kidney function decline in older adults: a comparison using creatinine and cystatin C

BACKGROUND/AIMS

The aim of this study was to determine the decline in the estimated glomerular filtration rate (eGFR) in elderly persons and to compare estimates based on creatinine and cystatin C.

METHODS

In the Cardiovascular Health Study, GFR changes in an elderly cohort were estimated from serum creatinine and cystatin C measured at baseline, year 3 and year 7 in 4,380 participants (age 72 +/- 5 years at entry). Outcomes were mean eGFR decline, incident chronic kidney disease (CKD) and rapid decline in eGFR (annual loss >3 ml/min/1.73 m(2)).

RESULTS

Mean annual eGFR loss as estimated from creatinine was 0.4 +/- 3.6 ml/min/1.73 m(2), with 16% of the participants experiencing a rapid decline. Mean eGFR loss as estimated from cystatin C was 1.8 +/- 2.6, with 25% of the participants experiencing a rapid decline (p < 0.001 for both). Among participants without baseline CKD, incident CKD was detected at year 7 in 10% (n = 263) using creatinine and 19% (n = 544) using cystatin C (p < 0.001). Increasing age was the strongest predictor of rapid decline; adjusted odds ratios were 1.38 (1.16-1.65), 1.62 (1.31-1.99) and 2.96 (2.28-3.84) for participants aged 70-74, 75-79 and 80+ at baseline, compared with those aged 65-69.

CONCLUSION

In elderly persons, cystatin C estimated substantially larger declines in kidney function than creatinine did. Defining the optimal measurement of kidney function in elderly persons should be a high priority for future research.

The epidemic challenge of chronic kidney disease in older patients

Since the introduction of estimated glomerular filtration rate (GFR), the number of patients with chronic kidney disease (CKD) has considerably increased. This is particularly true for elderly patients as the majority have a low GFR. Chronic kidney disease has a significant impact on a patient's outcome. We have reviewed important aspects of CKD in older patients, with emphasis on diagnosis and management, as well as explored decision-making regarding specialist-care referral and renal replacement therapy.

[Old age and the kidneys]

Age-related changes in renal morphology and function cannot be regarded physiological. The number of glomeruli falls, sclerotic glomeruli and aglomerular arterioles develop. Besides tubular atrophy interstitial fibrosis is often seen, and the age-related vascular changes strongly affect the kidneys. Renal blood flow and GFR decrease, without concomitant changes in se-creatinine. Disorders of tubular transport manifest mainly in salt- and water-excretion and lead to hyposthenuria. The pathogenesis of these age-related changes is not fully understood. Nevertheless, such changes impair the excretory functions and the pharmacokinetics of drugs. In real chronic renal failure other functions (erythropoietin production, vitamin-D, Ca and P metabolism) are also impaired. Due to more frequent occurrence of systemic diseases (diabetes, hypertension, etc.) in the elderly, real chronic renal failure is also more common, and various forms of acute renal failure develop more easily.

Comparison of proposed alternative methods for rescaling dialysis dose: resting energy expenditure, high metabolic rate organ mass, liver size, and body surface area

A number of denominators for scaling the dose of dialysis have been proposed as alternatives to the urea distribution volume (V). These include resting energy expenditure (REE), mass of high metabolic rate organs (HMRO), visceral mass, and body surface area. Metabolic rate is an unlikely denominator as it varies enormously among humans with different levels of activity and correlates poorly with the glomerular filtration rate. Similarly, scaling based on HMRO may not be optimal, as many organs with high metabolic rates such as spleen, brain, and heart are unlikely to generate unusually large amounts of uremic toxins. Visceral mass, in particular the liver and gut, has potential merit as a denominator for scaling; liver size is related to protein intake and the liver, along with the gut, is known to be responsible for the generation of suspected uremic toxins. Surface area is time-honored as a scaling method for glomerular filtration rate and scales similarly to liver size. How currently recommended dialysis doses might be affected by these alternative rescaling methods was modeled by applying anthropometric equations to a large group of dialysis patients who participated in the HEMO study. The data suggested that rescaling to REE would not be much different from scaling to V. Scaling to HMRO mass would mandate substantially higher dialysis doses for smaller patients of either gender. Rescaling to liver mass would require substantially more dialysis for women compared with men at all levels of body size. Rescaling to body surface area would require more dialysis for smaller patients of either gender and also more dialysis for women of any size. Of these proposed alternative rescaling measures, body surface area may be the best, because it reflects gender-based scaling of liver size and thereby the rate of generation of uremic toxins.

Sexual dimorphism of the aging kidney: role of nitric oxide deficiency

GFR falls with aging in humans and rats due to renal vasoconstriction and structural damage. The rate of deterioration is influenced by race/genetic background, environment, and sex, with females protected. Part of the female advantage relates to protective effects of estrogens. There is little information on impact of aging on the distribution/cardiovascular actions of the estrogen receptor subtypes. In rats, androgens may contribute to injury, but in men, high testosterone levels predict cardiovascular health. In women, the association is controversial. Nitric oxide deficiency contributes to the hypertension and renal dysfunction of aging, which may be delayed in the female.

Long-term effects of renin-angiotensin system-blocking therapy and a low blood pressure goal on progression of hypertensive chronic kidney disease in African Americans

BACKGROUND

Antihypertensive drugs that block the renin-angiotensin system (angiotensin-converting enzyme inhibitors [ACEIs] or angiotensin receptor blockers) are recommended for patients with chronic kidney disease (CKD). A low blood pressure (BP) goal (BP, <130/80 mm Hg) is also recommended. The objective of this study was to determine the long-term effects of currently recommended BP therapy in 1094 African Americans with hypertensive CKD.

METHODS

Multicenter cohort study following a randomized trial. Participants were 1094 African Americans with hypertensive renal disease (glomerular filtration rate, 20-65 mL/min/1.73 m2). Following a 3x2-factorial trial (1995-2001) that tested 3 drugs used as initial antihypertensive therapy (ACEIs, calcium channel blockers, and beta-blockers) and 2 levels of BP control (usual and low), we conducted a cohort study (2002-2007) in which participants were treated with ACEIs to a BP lower than 130/80 mm Hg. The outcome measures were a composite of doubling of the serum creatinine level, end-stage renal disease, or death.

RESULTS

During each year of the cohort study, the annual use of an ACEI or an angiotensin receptor blocker ranged from 83.7% to 89.0% (vs 38.5% to 49.8% during the trial). The mean BP in the cohort study was 133/78 mm Hg (vs 136/82 mm Hg in the trial). Overall, 567 participants experienced the primary outcome; the 10-year cumulative incidence rate was 53.9%. Of 576 participants with at least 7 years of follow-up, 33.5% experienced a slow decline in kidney function (mean annual decline in the estimated glomerular filtration rate, <1 mL/min/1.73 m2).

CONCLUSION

Despite the benefits of renin-angiotensin system-blocking therapy on CKD progression, most African Americans with hypertensive CKD who are treated with currently recommended BP therapy continue to progress during the long term.

Slower decline of glomerular filtration rate in the Japanese general population: a longitudinal 10-year follow-up study

The prevalence of stage 3 to 5 chronic kidney disease (CKD) in Japan (18.7%) is considerably higher than that in the United States (4.5%). This study investigated in the Japanese general population whether this higher prevalence of CKD might reflect to a progressive decline of renal function, and in turn to the increased risk of end-stage renal disease. A decline in renal function over 10 years was examined in 120,727 individuals aged 40 years or older who participated in the annual health examination program of the two periods over 10 years, 1988-1993 and 1998-2003. Renal function was assessed with estimated glomerular filtration rate (GFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) Study equation modified by a Japanese coefficient. The rate of GFR decline in the participants was 0.36 mL/min/1.73 m2/year on average. In the male population aged 50-79, the mean rate of GFR decline was significantly higher in the presence of hypertension than in its absence. The rate of GFR decline was more than two times higher in participants with proteinuria than in those without proteinuria in both sexes. The rate was significantly higher in participants with an initial GFR<50 mL/min/1.73 m2 among the groups younger than age 70 and in participants with an initial GFR<40 mL/min/1.73 m2 in the group with age 70-79. Based on the slow rate of GFR decline, we concluded that the decline in renal function progresses slowly in the Japanese general population. Hypertension, proteinuria and lower GFR were found to be significant risk factors for a faster decline of GFR.

Oral estrogen therapy in postmenopausal women is associated with loss of kidney function

Women are generally protected against progressive loss of kidney function; however, this advantage seems to diminish with menopause. Because of conflicting reports on the association between use of hormone therapy and kidney function we studied 5845 women (1459 on hormone therapy and 4386 non-users) who were over 66 years of age and had at least 2 serum creatinine measurements during the 2 year study period. After adjustment for covariates, hormone use (estrogen-only, progestin-only, or both) was associated with a significant loss of estimated GFR as the primary outcome along with an increased risk of rapid loss of kidney function as the secondary outcome compared to non-users. This increased rate of loss was associated with oral but not transvaginal estrogen use. An increased cumulative dose of estrogen was also associated with a greater decline in estimated GFR. Our study shows an independent association in a dose-dependent manner of estrogen use and loss of kidney function in this elderly population.

Prevalence of chronic kidney disease in population-based studies: systematic review

BACKGROUND

Chronic kidney disease (CKD) is becoming a major public health problem worldwide. This article reviews the published evidence of prevalence of CKD in population-based study samples that used the standardized definition from the Kidney Disease Outcomes Quality Initiative of the National Kidney Foundation (K/DOQI) practice guideline, and particularly focus on performance of serum-creatinine based equations for GFR estimation. We provide a summary of available data about the burden of CKD in various populations.

METHODS

We performed a systematic review of available published data in MEDLINE. A combination of various keywords relevant to CKD was used in this research. Related data of included studies were extracted in a systematic way.

RESULTS

A total of 26 studies were included in this review. The studies were conducted in different populations, and the number of study participants ranged from 237 to 65181. The median prevalence of CKD was 7.2% in persons aged 30 years or older. In persons aged 64 years or older prevalence of CKD varied from 23.4% to 35.8%. Importantly, the prevalence of CKD strongly depended on which estimating equations were used. The Modification of Diet in Renal Disease Study (MDRD) equation was likely to be preferred in recent epidemiological studies compared to the adjusted Cockcroft-Gault (CG) equation.

CONCLUSION

Worldwide, CKD is becoming a common disease in the general population. Accurately detecting CKD in special groups remains inadequate, particularly among elderly persons, females or other ethnic groups such as Asians.

The detection of advanced chronic kidney disease by surveillance of elevated plasma creatinines--a five-year experience

BACKGROUND

The late referral of patients with advanced chronic renal failure to a nephrologist is multifactorial but also compromises the preparations for dialysis and is prejudicial to their survival on dialysis. Measures that prompt or hasten referral, will allow preparation for dialysis, control of complications and treatment of comorbid conditions.

METHODS

In June 2000, a programme was initiated to provide surveillance of plasma creatinines >300 micromol/L on all laboratory requests from general practitioners (GPs) and hospital clinicians in Ayrshire and Arran Health Board in southwest Scotland. Patients already known to the nephrologists were excluded. Results were regularly reviewed and further excluded if the creatinine fell or the patient died. For the remainder, a standard letter was sent to the requesting clinician suggesting renal referral if appropriate. This was to act as a prompt to the general practitioner or hospital clinician. For those referred over the 5-year period, the outcome was analysed in January 2007.

RESULTS

In the first 5 years (June 2000-June 2005) letters were sent regarding 246 patients (median age 76). Fifty-three patients still had reversible ARF or died within 3 months of the letter; seven were already referred. The requesting clinician felt that referral was not appropriate in 56; 23 were being reviewed elsewhere. The programme has led to the referral of 50 patients to the renal service (and 3 to others) but in 54 cases no reply was received and the letter ignored. Of the 50 referred, 17 entered the dialysis programme, 13 of whom had definitive dialysis access (fistula or Tenckhoff catheter) at the start. After a period of outpatient review they have undergone a median of 21 months of dialysis.

CONCLUSIONS

Over the 5-year period this programme has detected a cohort of patients who, in general, benefited from nephrological follow-up and dialysis. It may also act as a prompt to clinicians to refer more 'marginal' patients and thereby hasten future referral.

Serum Creatinine Stabilization Following Renal Artery Stenting

The impact of renal artery stenting on renal function in a subgroup of consecutive de novo patients with atherosclerotic renal artery stenosis from the single operator, single center, retrospective renal stent trial is defined. Patients with inadequate preprocedure and/or follow-up renal function studies were excluded. Abnormal baseline serum creatinine (sCr) was defined as ≥1.5 mg/dL. Follow-up sCr was improved, unchanged, or worsened if the variance from baseline decreased by >20%, stayed within 20%, or increased >20%, respectively. For the total cohort (194 patients), renal function stabilized or improved in 72% of patients. Plotting 1/sCr demonstrated a decline in renal function before the procedure that stabilized following renal artery stenting. Bilateral renal artery stenting predicted normal follow-up sCr, and baseline sCr >2.1 mg/dL was associated with improvement in sCr long-term. In conclusion, renal artery stenting results in overall stabilization of renal function, and bilateral renal artery stenting seems to have added benefit.

Glucose metabolism, insulin resistance, and renal pathology in non-diabetic chronic kidney disease

BACKGROUND

The relation between insulin resistance and atherosclerosis is widely recognized, but it remains unknown whether glucose metabolism/insulin resistance is related to renal pathology in humans.

METHODS

We quantitatively evaluated pathological changes in the glomeruli, tubulointerstitium, and vessels in renal biopsy specimens from 23 patients with non-diabetic chronic kidney disease (CKD), all of whom took a 75-gram oral glucose tolerance test. We correlated the renal pathological changes with fasting plasma glucose (FPG), fasting plasma insulin, 2-hour plasma glucose (2-h PG), 2-hour plasma insulin (2-h PI), homeostasis model assessment of insulin resistance (HOMA-IR), and body mass index.

RESULTS

HOMA-IR exceeded 1.73 in 11 patients (47.8%), and 2-h PI exceeded 64.0 microU/ml in 14 (60.9%). FPG significantly correlated with interstitial fibrosis (r = 0.532, p = 0.009). The significance was marginal in the correlation between FPG and tubular atrophy and arterio-arteriolosclerosis. Statistically significant correlation was also found between 2-h PG and arterio-arteriolosclerosis (r = 0.422, p = 0.04) and between HOMA-IR and interstitial fibrosis (r = 0.416, p = 0.04).

CONCLUSION

Although precise mechanisms remain unknown, glucose metabolism/insulin resistance seem to play pathogenic roles in formation and progression of renal pathological changes, especially tubulointerstitial and vascular lesions, in non-diabetic CKD.

Dialysis in the elderly

More and more elderly (>65 years) patients are now reaching end-stage renal disease (ESRD) due to better management of co-morbid diseases. There are complex medical issues that need to be addressed when managing ESRD in this patient group. The option of dialysis in the elderly is a viable one. However, it needs careful consideration of patients' choices besides coexisting illnesses. Ideally, dialysis should prolong survival. However, an equally important issue is quality of life on dialysis. Life should be added to years and not years added to life. This often involves multidisciplinary input from various disciplines involved in patient care. Other than life on dialysis, the only other alternative is conservative management. Conservative management is not 'passive palliative therapy'. Rather, it involves active management of various clinical issues in a sick and vulnerable patient who does not have age on his side. All elderly patients have unique issues and no generalizations can be made. However, careful analysis makes it possible to offer dialysis to the right patient in the elderly and very elderly (>75 years and beyond) subgroups.