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Association Between Income Disparities and Risk of Chronic Kidney Disease

A Nationwide Cohort Study of Seven Million Adults in Korea

      Abstract

      Objective

      To examine the association between income level and incident chronic kidney disease (CKD) in adults with normal baseline kidney function.

      Patient and Methods

      We studied the association between income level categorized into deciles and incident CKD in a national cohort comprised of 7,405,715 adults who underwent National Health Insurance Service health examinations during January 1, 2009, to December 31, 2015, with baseline estimated glomerular filtration rates (eGFRs) ≥60 mL/min/1.73 m2. Incident CKD was defined as de novo development of eGFR <60 mL/min/1.73 m2 (model 1) or ≥25% decline in eGFR from baseline values accompanied by eGFR <60 mL/min/1.73 m2 (model 2).

      Results

      During a median follow-up of 4.8 years, there were 122,032 of 7,405,715 (1.65%) and 55,779 of 7,405,715 (0.75%) incident CKD events based on model 1 and 2 definitions, respectively. Compared with income levels in the sixth decile, there was an inverse association between lower income level and higher risk for CKD up to the fourth decile, above which no additional reduction (model 1) or slightly higher risk for CKD (model 2) was observed at higher income levels. The multivariable-adjusted hazard ratios from the lowest to fourth deciles were 1.30 (95% CI, 1.26-1.33), 1.16 (95% CI, 1.13-1.19), 1.07 (95% CI, 1.05-1.10), and 1.06 (95% CI, 1.03-1.09) in model 1 and 1.32 (95% CI, 1.27-1.37), 1.18 (95% CI, 1.14-1.22), 1.08 (95% CI, 1.04-1.13), and 1.05 (95% CI, 1.01-1.09) in model 2, respectively. These associations persisted across various subgroups of age, sex, and comorbidity status.

      Conclusion

      In this large nationwide cohort, lower income levels were associated with higher risk for incident CKD.

      Abbreviations and Acronyms:

      aHR (adjusted hazard ratio), CKD (chronic kidney disease), eGFR (estimated glomerular filtration rate), ESRD (end-stage renal disease), HR (hazard ratio), NHIS (National Health Insurance Service), SES (socioeconomic status)
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      Linked Article

      • Money Matters: Income and Risk of Chronic Kidney Disease in South Korea
        Mayo Clinic ProceedingsVol. 95Issue 2
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          There is little debate that socioeconomic factors such as income, education, and employment play fundamental roles in determining health outcomes, and their inequitable distribution is a root cause of health and health care disparities. Lower income is associated with a higher risk of all-cause mortality as compared with higher income,1 and the burden of numerous health conditions has been noted in many settings to be greater in persons with low socioeconomic status (SES).
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