Individual Income Status Correlates with Chronic Kidney Disease in Japan beyond Metabolic Risk Factors: Cross Sectional Study

Abstract

Background: Chronic kidney disease (CKD) is a pre-condition for end-stage kidney disease (ESKD) undergoing hemodialysis, as well as a risk factor for cardiovascular disease. Therefore, it is vital that CKD prevention measures be established. In particular, socioeconomic status (SES), as represented by income, contributes to non-communicable diseases like CKD. The purpose of this study was to examine the independent association between CKD and individual SES in Japan, with consideration of other metabolic risks. Methods: In the present study, we analyzed the 2011 National Health and Nutrition Survey by the Ministry of Health, Labor, and Welfare. Specifically, we analyzed 3,557 people out of 8,762 whose serum creatinine was measured. Logistic regression analysis was used to calculate the odds ratio (OR) of CKD by income distinction, after adjustment for age and metabolic risks (obesity, diabetes mellitus, dyslipidemia, and hypertension), which were assessed at the medical examination. Results: CKD was found in 385 participants (10.8%) and was associated with greater age, obesity, higher levels of low-density lipoprotein cholesterol, triglyceride, and glycated hemoglobin, and lower levels of hemoglobin and high-density lipoprotein cholesterol. The adjusted model indicated a significant association between lower income and CKD: the OR of the low income group (<2 million yen) was 1.33 (95% confidence interval: 1.01 - 1.78) in comparison with the high income group. Conclusions: The results of the present study indicate a substantial relationship between individual lower income status and CKD in Japan, where healthcare is easy to access. To prevent ESKD and cardiovascular diseases, early detection of CKD and its metabolic risks is necessary, especially among the socioeconomically vulnerable population.