Geographic Variation and US County Characteristics Associated With Rapid Kidney Function Decline

Abstract

Introduction: Geographic variation in the prevalence of chronic kidney disease and incidence of end-stage renal disease has been previously reported. However, the geographic epidemiology of rapid estimated glomerular filtration rate (eGFR) decline has not been examined.

Methods: We built a longitudinal cohort of 2,107,570 US veterans to characterize the spatial epidemiology of and examine the associations between US county characteristics and rapid eGFR decline.

Results: There were 169,029 (8.02%) with rapid eGFR decline (defined as eGFR slope < -5 ml/min per 1.73 m²/year). The prevalence of rapid eGFR decline adjusted for age, race, gender, diabetes, and hypertension varied by county from 4.10%-6.72% in the lowest prevalence quintile to 8.41%-22.04% in the highest prevalence quintile (P for heterogeneity < 0.001). Examination of adjusted prevalence showed substantial geographic variation in those with and without diabetes and those with and without hypertension (P for heterogeneity < 0.001). Cohort participants had higher odds of rapid eGFR decline when living in counties with unfavorable characteristics in domains including health outcomes (odds ratio [OR] = 1.15; confidence interval [CI] = 1.09-1.22), health behaviors (OR = 1.08; CI = 1.03-1.13), clinical care (OR = 1.11; CI = 1.06-1.16), socioeconomic conditions (OR = 1.15; CI = 1.09-1.22), and physical environment (OR = 1.15; CI = 1.01-1.20); living in counties with high percentage of minorities and immigrants was associated with rapid eGFR decline (OR = 1.25; CI = 1.20-1.31). Spatial analyses suggest the presence of cluster of counties with high prevalence of rapid eGFR decline.

Discussion: Our findings show substantial geographic variation in rapid eGFR decline among US veterans; the variation persists in analyses stratified by diabetes and hypertension status; results show associations between US county characteristics in domains capturing health, socioeconomic, environmental, and diversity conditions, and rapid eGFR decline.

Keywords: disparity in kidney disease; eGFR decline; geographic information systems; geographic variation; kidney function; spatial epidemiology.

Figure 1

Cohort construction. (a) Flow diagram of cohort assembly. (b) Timeline of cohort selection. eGFR, estimated glomerular filtration rate; ESRD, end-stage renal disease.

Figure 2

Crude prevalence of rapid estimated glomerular filtration rate decline. Prevalence represents number per 100 US veterans.

Figure 3

Adjusted prevalence of rapid estimated glomerular filtration rate decline. Adjusted for age, race, gender, diabetes, and hypertension. Prevalence represents number per 100 US veterans.

Figure 4

Median prevalence of rapid eGFR decline by (a) hypertension and (b) diabetes status. Adjusted for age, race, and gender. Prevalence represents number per 100 US veterans by disease status. Prevalence rates are grouped by county quintiles that are defined as the quintiles of age-, race-, and gender-adjusted prevalence in the overall cohort. Error bars represent IQR. CI, confidence interval; IQR, interquartile range.

Figure 5

Geographic clustering of rapid estimated glomerular filtration rate decline prevalence. Adjusted for age, race, gender, diabetes, and hypertension. Median (confidence interval) prevalence represents number per 100 US veterans.