Search

Higher levels of albumin excretion within the normal range are associated with cardiovascular disease in high-risk individuals. Whether incremental increases in urinary albumin excretion, even within the normal range, are associated with the development of hypertension in low-risk individuals is unknown. This study included 1065 postmenopausal women from the first Nurses' Health Study and 1114 premenopausal women from the second Nurses' Health Study who had an albumin/creatinine ratio

Black women are less likely to develop kidney stones and have greater bone mass than white women. However, little is known about racial differences in urine composition. Urine pH, volume, and 24-h urinary excretion of calcium, citrate, oxalate, uric acid, sodium, potassium, magnesium, phosphate, sulfate, and creatinine of 146 black women were compared with 330 white women in the Nurses' Health Study. All participants were postmenopausal non-stone formers. ANOVA was used to compare mean urinary values. Linear regression models were adjusted for age, body mass index, dietary intake, and urinary factors. On average, black women excreted 65 mg less urinary calcium (P < 0.001), 4 mg more oxalate (P < 0.001), 9 mEq less potassium (P < 0.001), 11 mg less magnesium (P = 0.003), 120 mg less phosphate (P < 0.001), and 3 mmol less sulfate (P < 0.001) per day than did white women. The urine pH of black women was 0.11 units higher (P = 0.03) and urine volume was 0.24 L less (P = 0.001). The urinary relative supersaturations of calcium oxalate (P = 0.03) and brushite (P = 0.002) were lower in black women. No other significant differences were observed. Differences in urinary calcium and pH persisted after multivariate adjustment and after exclusion of participants who were taking thiazide diuretics or those with diabetes. In conclusion, black women excrete less urinary calcium and have a higher urinary pH than do white women. These differences are not explained by differences in age, body mass index, or diet and may account for the lower incidence of both nephrolithiasis and osteoporosis in black women.

Despite improvements in intensive care and dialysis, some experts have concluded that outcomes associated with acute renal failure (ARF) have not improved significantly over time. ARF was studied in hospitalized patients between 1988 and 2002 using the Nationwide Inpatient Sample, a nationally representative sample of discharges from acute-care, nonfederal hospitals. During a 15-yr period, 5,563,381 discharges with ARF and 598,768 with ARF that required dialysis (ARF-D) were identified. Between 1988 and 2002, the incidence of ARF rose from 61 to 288 per 100,000 population; the incidence of ARF-D increased from 4 to 27 per 100,000 population. Between 1988 and 2002, in-hospital mortality declined steadily in patients with ARF (40.4 to 20.3%; P < 0.001) and in those with ARF-D (41.3 to 28.1%; P < 0.001). Compared with 1988 to 1992, the multivariable-adjusted odds ratio (OR) of death was lower in 1993 to 1997 (ARF: OR 0.62, 95% confidence interval [CI] 0.61 to 0.64; ARF-D: OR 0.63, 95% CI 0.59 to 0.66) and 1998 to 2002 (ARF: OR 0.40, 95% CI 0.39 to 0.41; ARF-D: OR 0.47, 95% CI 0.45 to 0.50). The percentage of patients who had ARF with a Deyo-Charlson comorbidity index of 3 or more increased from 16.4% in 1988 to 26.6% in 2002 (P < 0.001). This study provides evidence from an administrative database that the incidence of ARF and ARF-D is rising. Despite an increase in the degree of comorbidity, in-hospital mortality has declined.

Diet plays an important role in the pathogenesis of kidney stones. Because the metabolism of many dietary factors, such as calcium, may change with age, the relation between diet and kidney stones may be different in older adults. Uncertainty also remains about the association between many dietary factors, such as vitamin C, magnesium, and animal protein, and the risk of kidney stone formation. To examine the association between dietary factors and the risk of incident, symptomatic kidney stones in men and to determine whether these associations vary with age, a prospective cohort study was conducted of 45,619 men without a history of nephrolithiasis. Self-administered food frequency questionnaires were used to assess diet every 4 yr. A total of 1473 incident symptomatic kidney stones were documented during 477,700 person-years of follow-up. For men aged

Homocysteine is implicated to be an atherogenic amino acid and has been associated with increased risk of adverse cardiovascular outcomes. The prognostic significance of plasma total homocysteine (tHcy) levels for mortality and allograft loss in kidney transplant recipients has not been established. A total of 733 kidney transplant recipients who were seen for a routine visit at this transplant clinic in 1996 to 1998 were studied prospectively. During that visit, clinical information was collected and blood was drawn for laboratory evaluation. Information on the previous transplant procedure and the organ donor was obtained from the Eurotransplant Foundation database. Patients were followed prospectively using the Austrian Dialysis and Transplant Registry. With the use of proportional-hazards regression, the independent relations of fasting plasma tHcy levels to the risk of death from any cause and kidney allograft loss were examined. During a median follow-up of 6.1 yr, 154 participants died and 260 kidney allografts were lost. After adjustment for several important risk factors, elevated tHcy levels (/=12 micromol/L) were associated with 2.44 times the mortality risk of patients with normal tHcy levels (hazards ratio 2.44; 95% confidence interval 1.45 to 4.12; P0.001). Similarly, elevated tHcy levels were associated with 1.63 times increased risk of kidney allograft loss (hazards ratio 1.63; 95% confidence interval 1.09 to 2.44; P = 0.02). In this single-center sample, baseline fasting plasma tHcy levels were independently associated with the risk of death and kidney allograft loss. The clinical utility of homocysteine-lowering therapy, such as multivitamin therapy, to reduce the rates of these end points needs to be studied.

Many epidemiologic studies presently aim to evaluate the effect of risk factors on renal function. As direct measurement of renal function is cumbersome to perform, epidemiologic studies generally use an indirect estimate of renal function. The consequences of using different methods of renal function measurement in studies that evaluate the effect of cardiovascular risk factors on renal function were questioned. Data of the 8592 Prevention of Renal and Vascular End-stage Disease study participants, in whom the association was plotted between various cardiovascular risk factors and renal function measured either by creatinine clearance based on two 24-h urine collections or by the Cockcroft-Gault or Modification of Diet in Renal Disease formula were used. A repeated measurement analysis was used to compare the slopes of the linear regression lines of the risk factors and the different methods of renal function measurements. The relation between cardiovascular risk factors and renal function seems to be different when different methods for renal function are used. This was most pronounced for age, weight, and body mass index and less pronounced (but still statistical significant) for BP, cholesterol, and glucose. The relation between weight or body mass index and renal function showed completely different directions, depending on the renal function method used. In conclusion, the interpretation of the relation of cardiovascular risk factors and renal function is affected by the method selected to estimate renal function. For studying the relation of risk factors and renal function in large population studies, indirect estimates of renal function should be used with caution.

Despite extensive knowledge about abnormal lipid patterns in patients with end-stage renal disease, the association between cholesterol and the development of renal dysfunction is unclear. We evaluated this association in a prospective cohort study among 4,483 initially healthy men participating in the Physicians' Health Study who provided blood samples in 1982 and 1996. Main outcome measures were elevated creatinine, defined as >/= 1.5 mg/dl (133 micromol/L), and reduced estimated creatinine clearance, defined as /= 240 mg/dl), HDL (/= 40 mg/dl), total non-HDL cholesterol, and the ratio of total cholesterol to HDL. We used logistic regression to calculate age- and multivariable adjusted odds ratios as a measure for the relative risk. After 14 yr, 134 men (3.0%) had elevated creatinine and 244 (5.4%) had reduced creatinine clearance. The multivariable relative risk for elevated creatinine was 1.77 (95% confidence interval [CI], 1.10 to 2.86) for total cholesterol >/= 240 mg/dl, 2.16 (95% CI, 1.42 to 3.27) for HDL /= >6.8), and 2.16 (95% CI, 1.22 to 3.80) for the highest quartile of non-HDL cholesterol (>/= 196.1). Similar although smaller associations were observed between cholesterol parameters and reduced creatinine clearance. Elevated total cholesterol, high non-HDL cholesterol, a high ratio of total cholesterol/HDL, and low HDL in particular were significantly associated with an increased risk of developing renal dysfunction in men with an initial creatinine

Limited data suggest that HMG-CoA reductase inhibitors (statins) may slow loss of renal function in individuals with chronic renal insufficiency. This study was conducted to determine whether pravastatin reduced rates of loss of renal function in people with moderate chronic renal insufficiency. This was a post hoc subgroup analysis of a randomized double-blind placebo controlled trial. Data were analyzed from the CARE study (a randomized trial of pravastatin versus placebo in 4159 participants with previous myocardial infarction and total plasma cholesterol < 240 mg/dl). Participants with estimated GFR (MDRD-GFR) < 60 ml/min per 1.73 m(2) body surface area at baseline were considered to have moderate chronic renal insufficiency. Multivariate regression was used to calculate rates of decline in MDRD-GFR for individuals receiving pravastatin and placebo, controlling for prospectively determined covariates that might influence rates of renal function loss. Change in renal function could be calculated in 3384 individuals, of whom 690 (20.4%) had MDRD-GFR < 60 ml/min per 1.73 m(2) and were eligible for inclusion. Among all individuals with MDRD-GFR < 60 ml/min per 1.73 m(2)), the MDRD-GFR decline in the pravastatin group was not significantly different from that in the placebo group (0.1 ml/min per 1.73 m(2)/yr slower; 95% CI, -0.2 to 0.4; P = 0.49). However, there was a significant stepwise inverse relation between MDRD-GFR before treatment and slowing of renal function loss with pravastatin use, with more benefit in those with lower MDRD-GFR at baseline (P = 0.04). Rate of change in MDRD-GFR in the pravastatin group was 0.6 ml/min per 1.73 m(2)/yr slower than placebo (95% CI, -0.1 to 1.2; P = 0.07) in those with MDRD-GFR < 50 ml/min, and 2.5 ml/min per 1.73 m(2)/yr slower (95% CI, 1.4 to 3.6 slower; P = 0.0001) in those with MDRD-GFR < 40 ml/min per 1.73 m(2)/yr. Pravastatin also reduced rates of renal loss to a greater extent in participants with than without proteinuria at baseline (P = 0.006). It is concluded that pravastatin may slow renal function loss in individuals with moderate to severe kidney disease, especially those with proteinuria. These findings require confirmation by a large randomized trial conducted specifically in people with chronic renal insufficiency.

Menopause is associated with increased urinary calcium excretion, which could increase the risk for the development of calcium-containing kidney stones. However, it is unknown whether menopause and postmenopausal hormone (PMH) use are independent risk factors for incident kidney stone disease in women. Data from 91,731 female Nurses' Health Study participants who provided information on diet, menopause status, and kidney stone disease were used to examine the independent association between menopause and PMH use and risk of incident kidney stones. No association was found between menopause and incident kidney stones in age-adjusted (relative risk [RR], 1.07; 95% CI, 0.85 to 1.34) or multivariate models (RR, 1.12; 95% CI, 0.89 to 1.41). However, when the association between the type of menopause and risk of incident kidney stones was examined, surgical menopause was associated with an increased risk in both the age-adjusted (RR, 1.37; 95% CI, 1.05 to 1.77) and multivariate models (RR, 1.39; 95% CI, 1.07 to 1.81), whereas natural menopause was not. Compared with never-use, past or current PMH use (including duration of PMH use) was not associated with incident kidney stones among postmenopausal women. In conclusion, no association was found between menopause and PMH use and incident kidney stones. Surgical menopause, however, may be associated with an increased risk.

Anemia associated with chronic renal insufficiency (CRI) may have substantial clinical and public health importance, but little is known about its epidemiology. This study aims to quantify the relationship between reduced renal function and hemoglobin level, to assess the iron status of subjects with CRI, and to estimate the burden of anemia associated with CRI. The Third National Health and Nutrition Examination Survey (NHANES III) (1988 to 1994) data on 15,971 adults aged18 yr with measurements of serum creatinine, hemoglobin, and iron profile were analyzed. General linear models were used to determine the relationship between hemoglobin level and Cockcroft-Gault creatinine clearance (CrCl) and to estimate the likelihood of anemia at different levels of renal function in different demographic subgroups. Sample weights were used to produce weighted regression parameters and population estimates. A statistically significant decrease in hemoglobin was apparent among men starting at CrClor =70 ml/min and among women starting at CrClor =50 ml/min. At any given level of CrCl, men had a larger decrease in hemoglobin than women. For example, compared with subjects with CrCl80 ml/min, the decrease in hemoglobin for subjects with CrCl 20 to 30 ml/min was 1.0 g/dl in women and 1.4 g/dl in men. A substantial number of subjects with CRI might not have sufficient iron stores to support erythropoiesis as judged by the NKF-K/DOQI transferrin saturation or serum ferritin targets. Among those with CrCl 20 to 30 ml/min, 46% of women and 19% of men had transferrin saturation20%, and 47% of women and 44% of men had serum ferritin100 ng/ml. Results estimate that 13.5 million US adults had CrClor =50 ml/min. The overall burden of CRI associated anemia, defined as hemoglobin11 g/dl, was 800,000 adults. The public health burden of anemia associated with CRI may be substantial, given the large number of people with CRI; and that even a modest reduction in renal function is associated with decreased hemoglobin level.

Urinary oxalate is an important determinant of calcium oxalate kidney stone formation. High doses of vitamin B6 may decrease oxalate production, whereas vitamin C can be metabolized to oxalate. This study was conducted to examine the association between the intakes of vitamins B6 and C and risk of kidney stone formation in women. The relation between the intake of vitamins B6 and C and the risk of symptomatic kidney stones were prospectively studied in a cohort of 85,557 women with no history of kidney stones. Semiquantitative food-frequency questionnaires were used to assess vitamin consumption from both foods and supplements. A total of 1078 incident cases of kidney stones was documented during the 14-yr follow-up period. A high intake of vitamin B6 was inversely associated with risk of stone formation. After adjusting for other dietary factors, the relative risk of incident stone formation for women in the highest category of B6 intake (or =40 mg/d) compared with the lowest category (3 mg/d) was 0.66 (95% confidence interval, 0.44 to 0.98). In contrast, vitamin C intake was not associated with risk. The multivariate relative risk for women in the highest category of vitamin C intake (or =1500 mg/d) compared with the lowest category (250 mg/d) was 1.06 (95% confidence interval, 0.69 to 1.64). Large doses of vitamin B6 may reduce the risk of kidney stone formation in women. Routine restriction of vitamin C to prevent stone formation appears unwarranted.