Risk Factors for Incident CKD in Black and White Americans: The REGARDS Study

Abstract

Rationale & objective: Little information exists on the incidence of and risk factors for chronic kidney disease (CKD) in contemporary US cohorts and whether risk factors differ by race, sex, or region in the United States.

Study design: Observational cohort study.

Setting & participants: 4,198 Black and 7,799 White participants aged at least 45 years, recruited from 2003 through 2007 across the continental United States, with baseline estimated glomerular filtration rate (eGFR)>60mL/min/1.73m² and eGFR assessed again approximately 9 years later.

Exposures: Age, sex, race (Black or White), region ("stroke belt" or other), education, income, systolic blood pressure, body mass index, diabetes, coronary heart disease, hyperlipidemia, smoking, and albuminuria.

Outcomes: (1) eGFR change and (2) incident CKD defined as eGFR<60mL/min/1.73m² and≥40% decrease from baseline or kidney failure.

Analytical approach: Linear regression and modified Poisson regression were used to determine the association of risk factors with eGFR change and incident CKD overall and stratified by race, sex, and region.

Results: Mean age of participants was 63±8 (SD) years, 54% were female, and 35% were Black. After 9.4±1.0 years of follow-up, CKD developed in 9%. In an age-, sex-, and race-adjusted model, Black race (β =-0.13; P<0.001) was associated with higher risk of eGFR change, but this was attenuated in the fully adjusted model (β=0.02; P=0.5). Stroke belt residence was independently associated with eGFR change (β =-0.10; P<0.001) and incident CKD (relative risk, 1.14 [95% CI, 1.01-1.30]). Albuminuria was more strongly associated with eGFR change (β of-0.26 vs-0.17; P=0.01 for interaction) in Black compared with White participants. Results were similar for incident CKD.

Limitations: Persons of Hispanic ethnicity were excluded; unknown duration and/or severity of risk factors.

Conclusions: Established CKD risk factors accounted for higher risk of incident CKD in Black versus White individuals. Albuminuria was a stronger risk factor for eGFR decrease and incident CKD in Black compared with White individuals. Living in the US stroke belt is a novel risk factor for CKD.

Keywords: CKD incidence; Chronic kidney disease (CKD); albuminuria; disparities; eGFR decline; estimated glomerular filtration rate (eGFR); geographical disparities; race differences; regional differences; renal function; risk factors; sex differences; stroke belt.