Britt B. Newsome

Long-term risk of mortality and end-stage renal disease among the elderly after small increases in serum creatinine level during hospitalization for acute myocardial infarction.

BACKGROUND Although small changes in creatinine level during hospitalization have been associated with risk of short-term mortality, associations with posthospitalization end-stage renal disease (ESRD) and long-term mortality are unknown. We assessed the relationship between change in serum creatinine levels up to 3.0 mg/dL and death and ESRD among elderly survivors of hospitalization for acute myocardial infarction. METHODS Retrospective cohort study of a nationally representative sample of Medicare beneficiaries admitted with acute myocardial infarction to nonfederal US hospitals between February 1994 and July 1995. Outcomes were mortality and ESRD through June 2004. RESULTS The 87 094 eligible patients admitted to 4473 hospitals had a mean age of 77.1 years; for the 43.2% with some creatinine increase, quartiles of increase were 0.1, 0.2, 0.3 to 0.5, and 0.6 to 3.0 mg/dL. Incidence of ESRD and mortality ranged from 2.3 and 139.1 cases per 1000 person-years, respectively, among patients with no increase to 20.0 and 274.9 cases per 1000 person-years in the highest quartile of creatinine increase. Compared with patients without creatinine increase, adjusted hazard ratios by quartile of increase were 1.45, 1.97, 2.36, and 3.26 for ESRD and 1.14, 1.16, 1.26, and 1.39 for mortality, with no 95% confidence intervals overlapping 1.0 for either end point. CONCLUSION In a nationally representative sample of elderly patients discharged after hospitalization for acute myocardial infarction, small changes in serum creatinine level during hospitalization were associated with an independent higher risk of ESRD and death.

Racial Differences in the Prevalence of Chronic Kidney Disease among Participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort Study

The racial disparity in the incidence of ESRD exemplified by the three- to four-fold excess risk among black compared with white individuals in the United States is not reflected in the prevalence of less severe degrees of impaired kidney function among black compared with white individuals. The four-variable Modification of Diet in Renal Disease study equation was used to evaluate the black-to-white prevalence of impaired kidney function with increasing severity of impairment among participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a nationally representative, population-based cohort of individuals who are 45 yr and older. An estimated GFR (eGFR)<60 ml/min per 1.73 m2 was present in 43.3% of the 20,667 REGARDS participants and was slightly less prevalent among black than white patients (33.7 versus 49.9%; prevalence odds ratio 0.51; 95% confidence interval [CI] 0.48 to 0.54). The lower prevalence among black patients was not uniform as eGFR declined. After controlling for other patient characteristics, the black-to-white odds ratio was 0.42 (95% CI 0.40 to 0.46) at an eGFR of 50 to 59 ml/min per 1.73 m2 and increased to 1.73 (95% CI 1.02 to 2.94) at an eGFR of 10 to 19 ml/min per 1.73 m2. The disparity in prevalence of impaired kidney function among white compared with black patients reversed as the severity of impaired kidney function increased. Factors that are responsible for the increasing prevalence of severely impaired kidney function among black patients remain to be determined.

Kidney Function, Albuminuria, and All-Cause Mortality in the REGARDS (Reasons for Geographic and Racial Differences in Stroke) Study

BACKGROUND Chronic kidney disease and albuminuria are associated with increased risk of all-cause mortality. STUDY DESIGN Prospective observational cohort study. SETTING & PARTICIPANTS 17,393 participants (mean age, 64.3 ± 9.6 years) in the REGARDS (Reasons for Geographic and Racial Differences in Stroke) Study. PREDICTOR Estimated glomerular filtration rate (eGFR), urinary albumin-creatinine ratio (ACR). OUTCOME All-cause mortality (710 deaths); median duration of follow-up, 3.6 years. MEASUREMENTS & ANALYSIS: Categories of eGFR (90 to <120, 60 to <90, 45 to <60, 30 to <45, and 15 to <30 mL/min/1.73 m(2)) and urinary ACR (<10 mg/g or normal, 10 to <30 mg/g or high normal, 30 to 300 mg/g or high, and >300 mg/g or very high). Cox proportional hazards models were adjusted for demographic factors, cardiovascular covariates, and hemoglobin level. RESULTS The background all-cause mortality rate for participants with normal ACR, eGFR of 90 to <120 mL/min/1.73 m(2), and no coronary heart disease was 4.3 deaths/1,000 person-years. Higher ACR was associated with an increased multivariable-adjusted HR for all-cause mortality within each eGFR category. Decreased eGFR was associated with a higher adjusted HR for all-cause mortality for participants with high-normal (P = 0.01) and high (P < 0.001) ACRs, but not those with normal or very high ACRs. LIMITATIONS Only 1 laboratory assessment for serum creatinine and ACR was available. CONCLUSIONS Increased albuminuria was an independent risk factor for all-cause mortality. Decreased eGFR was associated with increased mortality risk in those with high-normal and high ACRs. The mortality rate was low in the normal-ACR group and increased in the very-high-ACR group, but did not vary with eGFR in these groups.

Poverty and Racial Disparities in Kidney Disease: The REGARDS Study

There are pronounced disparities among black compared to white Americans for risk of end-stage renal disease. This study examines whether similar relationships exist between poverty and racial disparities in chronic kidney disease (CKD) prevalence. Methods: We studied 22,538 participants in the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort study. We defined individual poverty as family income below USD 15,000 and a neighborhood as poor if 25% or more of the households were below the federal poverty level. Results: As the estimated glomerular filtration rate (GFR) declined from 50–59 to 10–19 ml/min/ 1.73 m2, the black:white odds ratio (OR) for impaired kidney function increased from 0.74 (95% CI 0.66, 0.84) to 2.96 (95% CI 1.96, 5.57). Controlling for individual income below poverty, community poverty, demographic and comorbid characteristics attenuated the black:white prevalence to an OR of 0.65 (95% CI 0.57, 0.74) among individuals with a GFR of 59–50 ml/min/1.73 m2 and an OR of 2.21 (95% CI 1.25, 3.93) among individuals with a GFR between 10 and 19 ml/min/ 1.73 m2. Conclusion: Household, but not community poverty, was independently associated with CKD and attenuated but did not fully account for differences in CKD prevalence between whites and blacks.

Albuminuria and Racial Disparities in the Risk for ESRD

The causes of the increased risk for ESRD among African Americans are not completely understood. Here, we examined whether higher levels of urinary albumin excretion among African Americans contributes to this disparity. We analyzed data from 27,911 participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study who had urinary albumin-to-creatinine ratio (ACR) and estimated GFR (eGFR) measured at baseline. We identified incident cases of ESRD through linkage with the United States Renal Data System. At baseline, African Americans were less likely to have an eGFR <60 ml/min per 1.73 m(2) but more likely to have an ACR ≥ 30 mg/g. The incidence rates of ESRD among African Americans and whites were 204 and 58.6 cases per 100,000 person-years, respectively. After adjustment for age and gender, African Americans had a fourfold greater risk for developing ESRD (HR 4.0; 95% CI 2.8 to 5.9) compared with whites. Additional adjustment for either eGFR or ACR reduced the risk associated with African-American race to 2.3-fold (95% CI 1.5 to 3.3) or 1.8-fold (95% CI 1.2 to 2.7), respectively. Adjustment for both ACR and eGFR reduced the race-associated risk to 1.6-fold (95% CI 1.1 to 2.4). Finally, in a model that further adjusted for both eGFR and ACR, hypertension, diabetes, family income, and educational status, African-American race associated with a nonsignificant 1.4-fold (95% CI 0.9 to 2.3) higher risk for ESRD. In conclusion, the increased prevalence of albuminuria may be an important contributor to the higher risk for ESRD experienced by African Americans.

Associations of dietary fat with albuminuria and kidney dysfunction

BACKGROUND Diet represents a potentially important target for intervention in nephropathy, yet data on this topic are scarce. OBJECTIVES The objective was to investigate associations between dietary fats and early kidney disease. DESIGN We examined cross-sectional associations between dietary fats and the presence of high albuminuria (an established independent predictor of kidney function decline, cardiovascular disease, and mortality) or estimated glomerular filtration rate (eGFR) <60 mL ⋅ min(-1) ⋅ 1.73 m(-2) at baseline in 19,256 participants of the REGARDS (Reasons for Geographic and Racial Differences in Stroke) study, an ongoing cohort study in US adults aged ≥45 y at time of enrollment. We used logistic regression to assess associations between quintiles of total fat and subtypes of dietary fat (saturated, monounsaturated, polyunsaturated, and trans fat) and presence of high albuminuria or eGFR <60 mL ⋅ min(-1) ⋅ 1.73 m(-2). RESULTS After multivariable adjustment, only saturated fat intake was significantly associated with high albuminuria [for quintile 5 compared with quintile 1, odds ratio (OR): 1.33; 95% CI: 1.07, 1.66; P for trend = 0.04]. No significant associations between any type of fat and eGFR <60 mL · min(-1) · 1.73 m(-2) were observed. ORs between the highest quintile of saturated fat and eGFR <60 mL · min(-1) · 1.73 m(-2) varied by race with a borderline significant interaction term (ORs: 1.24 in whites compared with 0.74 in blacks; P for interaction = 0.05) in multivariable-adjusted models, but no other associations were significantly modified by race or diabetes status. CONCLUSION Higher saturated fat intake is significantly associated with the presence of high albuminuria, but neither total nor other subtypes of dietary fat are associated with high albuminuria or eGFR <60 mL · min(-1) · 1.73 m(-2).

Correlates of Anemia in American Blacks and Whites The REGARDS Renal Ancillary Study

For unclear reasons, anemia is more common in American blacks than whites. The authors evaluated anemia prevalence (using World Health Organization criteria) among 19,836 blacks and whites recruited in 2003-2007 for the REasons for Geographic And Racial Differences in Stroke Renal Ancillary study and characterized anemia by 3 anemia-associated conditions (chronic kidney disease, inflammation, and microcytosis). They used multivariable models to assess potential causes of race differences in anemia. Anemia was 3.3-fold more common in blacks than whites, with little attenuation after adjusting for demographic variables, socioeconomic factors, and comorbid conditions. Increasing age, residence in the US southeast, lower income, vascular disease, diabetes, hypertension, and never smoking were associated with anemia. Age, diabetes, and vascular disease were stronger correlates of anemia among whites than blacks (P < 0.05). Among those with anemia, chronic kidney disease was less common among blacks than whites (22% vs. 34%), whereas inflammation (18% vs. 14%) and microcytosis (22% vs. 11%) were more common. In this large, geographically diverse cohort, anemia was 3-fold more common in blacks than whites with different characteristics and correlates. Race differences in anemia prevalence were not explained by the factors studied. Future research into the causes and consequences of anemia in different racial groups is needed.

Trends in Hip Fracture Rates in US Hemodialysis Patients, 1993-2010

BACKGROUND Changes in mineral and bone disorder treatment patterns and demographic changes in the dialysis population may have influenced hip fracture rates in US dialysis patients in 1993-2010. STUDY DESIGN Retrospective follow-up study analyzing trends over time in hospitalized hip fracture rates. SETTING & PARTICIPANTS Using Medicare data, we created 2 point-prevalent study cohorts for each study year. Hemodialysis cohorts included patients with Medicare as primary payer receiving hemodialysis in the United States on January 1 of each year; non-end-stage renal disease (ESRD) cohorts included Medicare beneficiaries 66 years or older on January 1 of each year. FACTORS Age, sex, race, primary cause of ESRD, dual Medicare/Medicaid enrollment status, comorbid conditions. OUTCOMES Hip fracture rates. MEASUREMENTS Unadjusted hip fracture rates measured using number of events per 1,000 person-years in each year, then adjusted for patient characteristics. Poisson models estimated strata-specific event rates. RESULTS The observed number of first hospitalized hip fracture events and the adjusted hip fracture rate increased steadily from 1993 (831 events; 11.9/1,000 person-years), peaked in 2004 (3,256 events; 21.9/1,000 person-years), and decreased through 2010 (2,912 events; 16.6/1,000 person-years). The trend for the subset of hemodialysis patients 66 years or older was similar to the trend for the full hemodialysis cohort; however, it differed markedly in magnitude and pattern from the non-ESRD Medicare cohort, for which rates were substantially lower and slowly decreasing since 1996. LIMITATIONS Unable to provide causal explanations for observed changes; hip fractures identified through inpatient episodes; results do not describe hemodialysis patients without Medicare Parts A and B; laboratory values unavailable in the Medicare data set. CONCLUSIONS Temporal trends in hip fracture rates among Medicare hemodialysis patients differ markedly from the steadily decreasing trend in non-ESRD Medicare beneficiaries, showing a relatively rapid increase until 2004 and relatively rapid decrease thereafter. Further research is needed to define associated factors.

Racial differences in the incidence of chronic kidney disease.

BACKGROUND AND OBJECTIVES The incidence of ESRD is higher in African Americans than in whites, despite reports of a similar or lower prevalence of CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This study compared the incidence of CKD among young African-American and white adults over 20 years of follow-up in the community-based Coronary Artery Risk Development in Young Adults study. Participants included 4119 adults, 18-30 years of age, with an estimated GFR (eGFR) ≥60 ml/min per 1.73 m(2) at baseline. Incident CKD was defined as an eGFR <60 ml/min per 1.73 m(2) and a ≥25% decline in eGFR at study visits conducted 10, 15, and 20 years after baseline. RESULTS At baseline, the mean age of African Americans and whites was 24 and 26 years, respectively (P<0.001), and 56% and 53% of participants, respectively, were women (P=0.06). There were 43 incident cases of CKD during follow-up, 29 (1.4%) among African Americans and 14 (0.7%) among whites (P=0.02). The age- and sex-adjusted hazard ratio (HR) for incident CKD comparing African Americans to whites was 2.56 (95% confidence interval [95% CI], 1.35-5.05). After further adjustment for body mass index, systolic BP, fasting plasma glucose, and HDL cholesterol, the HR was 2.51 (95% CI, 1.25-5.05). After multivariable adjustment including albuminuria at year 10, the HR for CKD at year 15 or 20 was 1.12 (95% CI, 0.52-2.41). CONCLUSIONS In this study, the 20-year CKD incidence was higher among African Americans than whites, a difference that is explained in part by albuminuria.

Physical and psychological burden of chronic kidney disease among older adults.

Introduction: The purpose of the study is to determine if functional status and quality of life (QoL) vary with glomerular filtration rate (GFR) among older adults. Methods: We studied adults aged 45 years and older participating in the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort study. Data included demographic and health information, serum creatinine and hemoglobin, the 4-item Center for Epidemiologic Studies Depression Scale (CES-D-4), the 4-item Cohen’s Perceived Stress Scale (PSS-4), reported health status and inactivity and the Medical Outcomes Study Short Form-12 (SF-12) QoL scores. Results: CKD (GFR <60 ml/min/1.73 m2) was present in 11.6% of the subjects. As GFR declined, the SF-12 physical component score, adjusted for other participant attributes, declined from 38.9 to 35.9 (p = 0.0001). After adjustment for other risk factors, poorer personal health scores (p < 0.0001) and decreased physical activity (p < 0.0001) were reported as GFR declined. In contrast, after adjusting for other participant characteristics, depression scores and stress scores and the mental component score of the SF-12 were not associated with kidney function. Conclusion: Older individuals with CKD in the US population experience an increased prevalence of impaired QoL that cannot be fully explained by other individual characteristics.