Time trends in the association of ESRD incidence with area-level poverty in the US population.

The objective of this study was to examine the temporal trends of the association between area-level poverty status and end-stage renal disease (ESRD) incidence. We hypothesized that the association between area-level poverty status and ESRD incidence has increased significantly over time. Patient data from the United States Renal Data System were linked with data from the 2000 and 2010 US census. Area-level poverty was defined as living in a zip code-defined area with ≥20% of households living below the federal poverty line. Negative binomial regression models were created to examine the association between area-level poverty status and ESRD incidence by time period in the US adult population while simultaneously adjusting for the distribution of age, sex, and race/ethnicity within a zip code. Time was categorized as January 1, 1995 through December 31, 2004 (Period 1) and January 1, 2005 through December 31, 2010 (Period 2). The percentage of adults initiating dialysis with area-level poverty increased from 27.4% during Period 1 to 34.0% in Period 2. After accounting for the distribution of age, sex, and race/ethnicity within a zip code, area-level poverty status was associated with a 1.24 (95% confidence interval [CI] 1.22, 1.25)-fold higher ESRD incidence. However, this association differed by time period with 1.04-fold (95% CI 1.02, 1.05) higher ESRD incidence associated with poverty status for Period 2 compared with the association between ESRD and poverty status in Period 1. Area-level poverty and its association with ESRD incidence is not static over time.