Regional variation in the incidence of dialysis-requiring AKI in the United States

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.

Figures

Figure 1.

Population incidence rate of dialysis-requiring AKI and in-hospital incidence of dialysis-requiring AKI by regions from 2007 to 2009.

Figure 2.

Population incidence rate of dialysis-requiring AKI versus population incidence rate of ESRD by regions from 2007 to 2009. Error bars represent SEMs. No error bars are given for ESRD, because the population incidence rates for ESRD were obtained directly from the US Renal Data System and therefore, are not estimates.

Figure 3.

Population incidence rate of dialysis-requiring AKI versus case fatality rate by regions from 2007 to 2009. Error bars represent SEMs.