“Healthy citizens are the greatest asset any country can have.”
Diabetes and high blood pressure take a toll on the kidneys, especially in African Americans. To prevent chronic kidney disease (CKD) and to slow or stop its progression, the same principles apply in African Americans as in other patients—ie, vigilance for the onset of proteinuria, aggressive control of blood pressure, drug treatment to block the renin-angiotensin system, and attention to lifestyle factors (Table 1). However, we need to try to do better in the care of African Americans.
The purpose of this article is to review recent evidence- and consensus-based recommendations and to present a practical approach for the evaluation and treatment of CKD in African Americans.
In 2002, the National Kidney Foundation1 defined CKD as either:
- Kidney damage for 3 or more months, as defined by structural or functional abnormalities of the kidney, with or without a decreased glomerular filtration rate (GFR), manifested either by pathologic abnormalities or by markers of kidney damage, including abnormalities in the composition of the blood or urine (eg, proteinuria), or abnormalities in imaging tests; or
- A GFR less than 60 mL/min/1.73 m2 for 3 or more months, with or without kidney damage.
The definition divides CKD into five progressive stages according to the GFR:
- Stage 1 (kidney damage with normal or increased GFR): GFR ≥ 90 mL/min/1.73m2
- Stage 2 (kidney damage with mildly decreased GFR): GFR 60–89
- Stage 3 (moderately decreased GFR): GFR 30–59
- Stage 4 (severely decreased GFR): GFR 15–29
- Stage 5 (kidney failure): GFR < 15 or dialysis.
Because the definition includes markers of kidney damage such as albuminuria, it allows CKD to be detected in its earliest stages, when the estimated GFR might still be well within normal limits.
CKD APPEARS EARLIER, PROGRESSES FASTER IN AFRICAN AMERICANS
“Not everything that counts can be counted, and not everything that can be counted counts.”
CKD with or without a sustained reduction in the estimated GFR affects about one in every nine American adults.2 Its course varies depending on the cause and also from patient to patient, even in those with the same cause of CKD.
In general, the prevalence of early CKD is comparable across racial and ethnic groups in the United States, but CKD progresses to end-stage renal disease far more rapidly in minority populations, with rates nearly four times higher in black Americans than in white Americans.3 Also, the onset of CKD is earlier in African Americans.
HYPERTENSION AND DIABETES AS REASONS FOR THE DISPARITIES
Part of the reason for these differences is that minority populations have higher rates of diabetes and hypertension, and these diseases tend to be more severe in these groups. Poverty, less access to health care, exposure to environmental toxins, and genetic variation may also contribute.4–7
Compared with whites, blacks have higher rates of diabetes and hypertension and earlier onset of these diseases, poorer control, and higher rates of complications such as CKD, stroke, and heart disease.8,9 The higher rate of hypertension and the lower rate of blood pressure control in African Americans with CKD may contribute to the more rapid progression of CKD to end-stage renal disease.
In the Chronic Renal Insufficiency Cohort, 10 a racially and ethnically diverse group of 3,612 adults with a broad spectrum of renal disease severity, 93% of African Americans had hypertension at baseline compared with 80% of whites. In addition, African Americans were 18% less likely to have their blood pressure controlled to 140/90 mm Hg (the rates of control were 76% vs 60%), and 28% were less likely to have it controlled to 130/80 mm Hg (56% vs 38%).10 These factors may partially explain the faster progression to end-stage renal disease in African Americans with CKD.
Despite the potential efficacy of strict control of serum glucose levels and blood pressure,11 the high rate of poor blood pressure control has contributed to the epidemic of diabetic nephropathy, especially among African Americans. Fortunately, hypertension control in the general population, while still not ideal, has improved from 27% in 1988–1994 to 50% in 2007–2008 and is now similar across racial and ethnic groups.12 This, hopefully, is a preface for improved hypertension-related outcomes for all Americans over the next decade.