Abstract
BACKGROUND AND OBJECTIVES: Little is known about geographic differences in the incidence of AKI. The objective of this study was to determine if regional variation exists in the population incidence of dialysis-requiring AKI in the United States. DESIGN, SETTING, PARTICIPANTS, & METHODS: Data from the Nationwide Inpatient Sample, a US nationally representative sample of hospitalizations, were used to determine the incidence rates of dialysis-requiring AKI between 2007 and 2009 among the four US Census-designated regions. Cases were identified using validated discharge codes. Poisson regression models were used to estimate overall regional rates, accounting for the data's sampling scheme. RESULTS: In 2007-2009, the population incidence rates of dialysis-requiring AKI differed across the four Census-designated regions (P=0.04). Incidence was highest in the Midwest (523 cases/million person-yr, 95% confidence interval=483 to 568) and lowest in the Northeast (457 cases/million person-yr, 95% confidence interval=426 to 492). The pattern of regional variation in the incidence of dialysis-requiring AKI was not the same as the pattern of regional variation in the incidence of renal replacement therapy-requiring ESRD (obtained from the US Renal Data System). In-hospital mortality associated with dialysis-requiring AKI differed across the four regions, with the highest case fatality in the Northeast (25.9%) and the lowest case fatality in the Midwest (19.4%). CONCLUSIONS: Significant regional variation exists in the population incidence of dialysis-requiring AKI in the United States, and additional investigation is warranted to uncover potential causes behind these geographic differences.