Aortic stiffness and change in glomerular filtration rate and albuminuria in older people.

BACKGROUND: Aortic stiffness increases with age and increases pulsatile stress in the microcirculation. Abnormalities in kidney microvascular structure and function may contribute to development or progression of chronic kidney disease in older people. METHODS: We performed a longitudinal analysis of 629 community-dwelling elderly Icelandic adults from the Age, Gene/Environment Susceptibility-Reykjavik Study with two visits over a mean follow-up of 5.3 years. We evaluated the associations of carotid-femoral pulse wave velocity (CFPWV), carotid pulse pressure (CPP) and augmentation index (AI), with the change in estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR) assessed as annual change and dichotomized as large changes. Models were adjusted for age, sex, height, heart rate, traditional cardiovascular disease risk factors and baseline kidney measures. RESULTS: When eGFR was analyzed as a continuous variable, higher baseline CFPWV and CPP, but not AI, were significantly associated with a larger annual decline in eGFR in models adjusted for age, sex, height, heart rate and baseline eGFR, but not after additional adjustment for the mean arterial pressure. When eGFR was analyzed as a categorical variable, higher CFPWV was significantly associated with a decrease in eGFR of ≥3 mL/min/1.73 m 2 /year [odds ratio (OR) 1.53, 95% confidence interval (CI) 1.11-2.13] and higher AI was associated with 30% eGFR decline during follow-up (OR 1.44 and 95% CI 1.03-2.00) in fully adjusted models. None of the tonometry measures was associated with change in UACR. CONCLUSIONS: Abnormalities in vascular health may play a role in large declines in eGFR beyond the traditional cardiovascular disease risks in this older Icelandic cohort.

Comparing GFR Estimating Equations Using Cystatin C and Creatinine in Elderly Individuals.

Current guidelines recommend reporting eGFR using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations unless other equations are more accurate, and recommend the combination of creatinine and cystatin C (eGFRcr-cys) as more accurate than either eGFRcr or eGFRcys alone. However, preferred equations and filtration markers in elderly individuals are debated. In 805 adults enrolled in the community-based Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study, we measured GFR (mGFR) using plasma clearance of iohexol, standardized creatinine and cystatin C, and eGFR using the CKD-EPI, Japanese, Berlin Initiative Study (BIS), and Caucasian and Asian pediatric and adult subjects (CAPA) equations. We evaluated equation performance using bias, precision, and two measures of accuracy. We first compared the Japanese, BIS, and CAPA equations with the CKD-EPI equations to determine the preferred equations, and then compared eGFRcr and eGFRcys with eGFRcr-cys using the preferred equations. Mean (SD) age was 80.3 (4.0) years. Median (25th, 75th) mGFR was 64 (52, 73) ml/min per 1.73 m(2), and the prevalence of decreased GFR was 39% (95% confidence interval, 35.8 to 42.5). Among 24 comparisons with the other equations, CKD-EPI equations performed better in 9, similar in 13, and worse in 2. Using the CKD-EPI equations, eGFRcr-cys performed better than eGFRcr in four metrics, better than eGFRcys in two metrics, and similar to eGFRcys in two metrics. In conclusion, neither the Japanese, BIS, nor CAPA equations were superior to the CKD-EPI equations in this cohort of community-dwelling elderly individuals. Using the CKD-EPI equations, eGFRcr-cys performed better than eGFRcr or eGFRcys.

Midlife Blood Pressure and Late-Life GFR and Albuminuria: An Elderly General Population Cohort.

BACKGROUND: Chronic kidney disease (CKD) is common in the elderly, but the cause is often not identifiable. Some posit that age-related reductions in glomerular filtration rate (GFR) and increases in albuminuria are normal, whereas others suggest that they are a consequence of vascular disease. STUDY DESIGN: Cross-sectional analysis of a substudy of a prospective cohort. SETTING & PARTICIPANTS: AGES (Age, Gene/Environment Susceptibility)-Reykjavik Study. PREDICTOR: Exposure to higher blood pressure in midlife. OUTCOMES & MEASUREMENTS: Measured GFR using plasma clearance of iohexol and urine albumin-creatinine ratio. RESULTS: GFR was measured in 805 participants with mean age in midlife and late life of 51.0±5.8 and 80.8±4.0 (SD) years, respectively. Mean measured GFR was 62.4±16.5 mL/min/1.73 m(2) and median albuminuria was 8.0 (IQR, 5.4-16.5) mg/g. Higher midlife systolic and diastolic blood pressures were associated with lower later-life GFRs. Associations persisted after adjustment. Higher midlife systolic and diastolic blood pressures were also associated with higher albumin-creatinine ratios, and associations remained significant even after adjustment. LIMITATIONS: This is a study of survivors, and people who agreed to participate in this study were healthier than those who refused. Blood pressure may encompass effects of the other risk factors. Results may not be generalizable to populations of other races. We were not able to adjust for measured GFR or albuminuria at the midlife visit. CONCLUSIONS: Factors other than advanced age may account for the high prevalence of CKD in the elderly. Midlife factors are potential contributing factors to late-life kidney disease. Further studies are needed to identify and treat midlife modifiable factors to prevent the development of CKD.

Aortic stiffness and kidney disease in an elderly population.

BACKGROUND/AIMS: The causes of chronic kidney disease (CKD) in older people are not well understood. Aortic stiffness increases with age and results in the transmission of increased pulsatility into the kidney microvasculature, potentially contributing to CKD in older populations. METHODS: We utilized data from the Age, Gene/Environment, Susceptibility-Reykjavik Study, a community-based prospective cohort study of cardiovascular disease (CVD) in Iceland. The relationship of carotid pulse pressure (CPP) and carotid-femoral pulse wave velocity (CFPWV) with estimated glomerular filtration rate (eGFR) based on creatinine and cystatin C and urine albumin-creatinine ratio (ACR) was assessed using linear regression, adjusting for demographics and CVD risk factors. RESULTS: 940 participants (mean (SD) age 75.8 (4.7) years, mean (SD) CFPWV 12.9 (4.2) m/s, mean (SD) CPP 69 (21) mm Hg, mean (SD) eGFR 68 (16) ml/min/1.73 m(2), and median (IQR) ACR 3 (2-6) mg/g) were included in this study. At CPP greater than 85 mm Hg, a higher CPP was associated with a lower eGFR in unadjusted analyses but not after adjustment. CPP was significantly associated with a higher ACR in fully adjusted models (ß (95% CI) = 0.14 (0.03, 0.24) ln mg/g per SD). Higher CFPWV was associated with lower eGFR and higher ACR in unadjusted analyses but not after adjustment. CONCLUSION: Greater aortic stiffness may be associated with modestly higher levels of albuminuria in the elderly. The association between aortic stiffness and lower eGFR may be confounded by age and CVD risk factors.

HLA-B8, DR3: a new risk factor for graft failure after renal transplantation in patients with underlying immunoglobulin A nephropathy.

BACKGROUND: The HLA-B8, DR3 haplotype has been associated with high immune reactivity. In this study, we have tested whether this haplotype has differential effect on graft survival in patients with IgAN compared with control patients. METHODS: From the Eurotransplant Registry we analyzed graft survival of 1207 recipients with IgAN and 7935 control patients with non-glomerular diseases. Death-censored graft loss according to the HLA-B8, DR3 haplotype was calculated with Kaplan-Meier analysis and Cox-regression model was used to correct for various risk factors. RESULTS: The frequency of the HLA-B8, DR3 haplotype was significantly lower in IgAN patients compared with controls (10.3% vs. 15.4%, p < 0.001). Ten-year graft survival was identical in the control group with and without the HLA-B8, DR3 haplotype (71.1% and 70.2%, respectively), but significantly worse in IgAN patients carrying the HLA-B8, DR3 haplotype compared with patients without it (52.5% vs. 69.1%, respectively, p = 0.009). The risk of graft loss was increased by 66% (HR 1.6, 95% CI 1.14, 2.29) in IgAN with the HLA-B8, DR3 haplotype and independent of well-known risk factors. CONCLUSIONS: We have identified a new risk factor for graft loss unique to patients with IgAN. This finding emphasizes the exclusive immune characteristics of IgAN patients after transplantation.

Exclusive characteristics of graft survival and risk factors in recipients with immunoglobulin A nephropathy: a retrospective analysis of registry data.

BACKGROUND: Some studies have claimed that patients with immunoglobulin A (IgA) nephropathy have better graft survival than other renal graft recipients, whereas others have rejected this statement. We have addressed this paradox in the present study. METHODS: In all, 1,207 patients with IgA nephropathy who received a primary cadaveric renal graft from 1990 to 2002 were identified in the Eurotransplant database. For comparison, we analyzed 7,935 patients with nonglomerular diseases. Death-censored graft survival was calculated using Kaplan Meier estimates and a multivariable Cox regression analysis was used for risk calculations. RESULTS: Death-censored graft survival was superior in patients with IgA nephropathy in the first period after transplantation. After 3 years posttransplant, however, there was an accelerated decline in graft survival in recipients with IgA nephropathy. The fully adjusted risk of graft loss in the first year was increased by 40% in the control group compared to IgA nephropathy (hazard ratio [HR] 1.40, 95% CI 1.12-1.75), whereas the risk was significantly lower in the control group after the first year posttransplant (HR 0.75, 95% CI 0.63-0.88). Cold ischemia time, immunization and HLA-DR mismatch were risk factors for graft loss in the control group but not for IgA nephropathy, whereas HLA-AB mismatch was an independent risk factor, exclusively for the IgA nephropathy group. CONCLUSIONS: Recipients with IgA nephropathy have better 1-year graft survival, presumably due to favorable immunological behavior. This benefit was however abolished in the long-term by increased graft loss with time. Studies are needed to explain the difference in graft survival and the reason why different risk factors are involved in graft failure.

Incidence and outcome of acute phosphate nephropathy in Iceland.

BACKGROUND: Oral sodium phosphate solutions (OSPS) are widely used for bowel cleansing prior to colonoscopy and other procedures. Cases of renal failure due to acute phosphate nephropathy following OSPS ingestion have been documented in recent years, questioning the safety of OSPS. However, the magnitude of the problem remains unknown. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a population based, retrospective analysis of medical records and biopsies of all cases of acute phosphate nephropathy that were diagnosed in our country in the period from January 2005 to October 2008. Utilizing the complete official sales figures of OSPS, we calculated the incidence of acute phosphate nephropathy in our country. Fifteen cases of acute phosphate nephropathy were diagnosed per 17,651 sold doses of OSPS (0.085%). Nine (60%) were women and mean age 69 years (range 56-75 years). Thirteen patients had a history of hypertension (87%) all of whom were treated with either ACE-I or ARB and/or diuretics. One patient had underlying DM type I and an active colitis and one patient had no risk factor for the development of acute phosphate nephropathy. Average baseline creatinine was 81.7 µmol/L and 180.1 at the discovery of acute renal failure, mean 4.2 months after OSPS ingestion. No patient had a full recovery of renal function, and at the end of follow-up, 26.6 months after the OSPS ingestion, the average creatinine was 184.2 µmol/L. The average eGFR declined from 73.5 ml/min/1.73 m(2) at baseline to 37.3 ml/min/1.73 m(2) at the end of follow-up. One patient reached end-stage renal disease and one patient died with progressive renal failure. CONCLUSION/SIGNIFICANCE: Acute phosphate nephropathy developed in almost one out of thousand sold doses of OSPS. The consequences for kidney function were detrimental. This information can be used in other populations to estimate the impact of OSPS. Our data suggest that acute phosphate nephropathy may be greatly underreported worldwide.

Prevalence of chronic kidney disease based on estimated glomerular filtration rate and proteinuria in Icelandic adults.

BACKGROUND: The purpose of this study was to compare three different equations to calculate estimated glomerular filtration rate (eGFR) based on serum creatinine (SCr) and to estimate the prevalence of chronic kidney disease (CKD) in the Icelandic population. METHODS: This was a cross-sectional study using data from the Reykjavik Heart Study. GFR was estimated with three equations: Equation I was based on 1/SCr; Equation II based on the Cockcroft-Gault equation; and Equation III was the modified MDRD equation. The eGFR calculated with Equation III and proteinuria were used to estimate the prevalence of CKD. The prevalence was age-standardized to the truncated world population. We used chi-square and ANCOVA to compare the group with low eGFR to age-matched controls. RESULTS: The subjects consisted of 9229 males and 10,027 females, aged 33-85 years. The equations performed very differently. Equation I showed women with higher eGFR than men and little change with age. Equation II showed men with higher eGFR than women and marked decline in eGFR with age. Equation III was similar to Equation II but the decline in eGFR with age was not as great. Regardless of the equation used, most subjects (63.7-80.7%) had an eGFR in the range of 60-89 ml/min/1.73 m2. Using Equation III, age-standardized prevalence of low eGFR for the population aged 35-80+ years was estimated to be 4.7 and 11.6% for men and women, respectively. The proportion of subjects with eGFR <60 ml/min/1.73 m2 increased with advancing age. An additional 2.39% of men and 0.89% of women had proteinuria. The prevalence of renal and cardiovascular risk factors including proteinuria, hypertension, lipid abnormalities and markers of inflammation was higher among those with low eGFR than age-matched controls. CONCLUSIONS: GFR estimates and the prevalence of CKD are dependent on the equation used to calculate eGFR. Unexpectedly, a low proportion of the Icelandic population had normal kidney function according to the eGFR regardless of the equation used. These equations may not be useful in epidemiological research.

Erythrocyte sedimentation rate, an independent predictor of coronary heart disease in men and women: The Reykjavik Study.

The relation between erythrocyte sedimentation rate (ESR) and risk of developing coronary heart disease (CHD) or fatal cerebrovascular accident was assessed in a cohort of 7,988 men and 8,685 women who participated in The Reykjavik Study (Iceland). Cardiovascular risk assessment was based on characteristics at baseline, from 1967 to 1996. During an average follow-up of 19 and 20 years, 2,092 men and 801 women, respectively, developed CHD, and 251 men and 178 women died from cerebrovascular accident. For men, the fully adjusted increase in risk of developing CHD predicted by the top compared with the bottom quintile of ESR was 57% (hazard ratio = 1.57, 95% confidence interval: 1.38, 1.78; p < 0.001); for women, risk was increased by 49% (hazard ratio = 1.49, 95% confidence interval: 1.16, 1.90; p < 0.001). The increased risk after baseline ESR measurement was stable for up to 25 years for men and 20 years for women. The fully adjusted risk of death due to stroke predicted by increasing the ln(ESR + 1) by one standard deviation was increased by 15% for men (p = 0.06) and 16% for women (p = 0.08). In conclusion, ESR is a long-term independent predictor of CHD in both men and women. These findings support the evidence of an inflammatory process in atherosclerosis.

Plasma exchange improves graft survival in patients with recurrent focal glomerulosclerosis after renal transplant.

Recurrence of primary focal glomerulosclerosis (FGS) after renal transplantation is associated with poor graft survival. Plasma exchange (PE) can reduce proteinuria and even induce complete remission of proteinuria. It is, however, unknown whether the use of PE therapy improves long-term graft survival. In our center, PE has been used to treat recurrent FGS after renal transplantation since 1994. Thus far, 13 patients have been treated with PE for recurrent FGS and followed for up to 77 months after the onset of the recurrence. We reviewed the transplantation data in these patients, and, for comparison, ten patients who underwent transplantation between 1973 and 1991 and were not treated with PE served as historical controls. Recurrence of FGS occurred within 4 weeks of transplantation in 74% of the patients. PE was started within 14 days of the onset of proteinuria in 85% of the patients. Two patients lost their graft within the first month of transplantation due to untreatable rejection; the remaining 11 patients (85%) achieved complete (n=7) or partial (n=4) remission. Seven patients remained in remission after a short period of treatment with PE (< or =18 sessions in 2 months), whereas four patients needed prolonged treatment (median of 58 sessions). The need for prolonged PE was associated with a late (>30 days after transplantation) recurrence of FGS (P=0.02). A comparison with the historical control group revealed not only a significant reduction in proteinuria, but also significantly better long-term graft survival in the treated group, 85% and 30%, respectively, at 5 years (P=0.02). In conclusion, PE is an effective form of treatment for recurrent FGS, especially if initiated early. Failure to maintain stable remission after the initial period of PE does not necessarily imply a poor outcome, and sustained remissions can be achieved after prolonged treatment.