Chronic kidney disease and outcomes in American Indian adults

Chronic kidney disease (CKD) is common in the U.S. adult population (~25% in those aged ≥60). Previous studies suggest that CKD may be more common in selected American Indian populations. We examined incidence and outcomes of CKD in a prospective cohort study (Strong Heart Study) of adults aged 45-74 from 13 American Indian tribes/communities in Arizona, Oklahoma, and the Dakotas. At first exam (6/89-1/92), there were 4,337 participants with information on albumin:creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR). Reexaminations were conducted in 1993–1995 and 1998–1999, and mortality was followed through 12/31/07. CKD was defined as ACR≥30 mg/g (stages 1-2) or eGFR<60 ml/min/m² (stages 3-5). One-third (34.3%) of participants had CKD at baseline. Among participants free of CKD at the baseline exam, 23.6% had CKD at the third exam, of whom 26.8% had more advanced CKD (stage 3-5). Only 0.3% of those without CKD at baseline progressed to end-stage renal disease (ESRD) by the third exam, but age- and gender-adjusted incidence of ESRD was 2.3%, 10.8%, and 34.3% among those with CKD stages 1, 2, and 3-5, respectively, at baseline. By the end of follow-up, 59.3% vs. 32.0% of participants with vs. without CKD at baseline had died of any cause; cardiovascular mortality was 22.4% vs.8.0%. CKD is highly prevalent in middle-aged and older American Indians, relative to the general population; progression to ESRD and cardiovascular and all-cause mortality may be related to excess diabetic nephropathy in this population.