Risk of Chronic Kidney Disease in Non-Obese Individuals with Clustering of Metabolic Factors: A Longitudinal Study

Objective The impact of the clustering of metabolic factors on chronic kidney disease (CKD) in non-obese individuals remains unclear. Methods We conducted a follow-up study of 23,894 Japanese adults (age, 18-69 years) who continuously received annual health examinations between 2000 and 2011. Obesity, high blood pressure, high triglycerides, low high-density lipoprotein (HDL) cholesterol and high fasting blood sugar were defined as metabolic factors, and CKD was defined as renal dysfunction (estimated glomerular filtration rate: <60 mL/min/1.73 m(2)) or proteinuria (dipstick test: >= 1+). The association between the clustering of metabolic factors and CKD was assessed based on the presence or absence of obesity using a Cox proportional hazard model. Results Of 2,867 subjects with >= 3 metabolic factors, 650 (22.7%) were non-obese. These individuals were older and had higher metabolic risks than their obese counterparts at baseline. Among the entire cohort of 23,894 subjects, 1,764 developed renal dysfunction and 904 developed proteinuria during an average follow-up period of 7.8 years. The cumulative incidence of renal dysfunction was higher (22.1% vs. 16.1%), whereas that of proteinuria was lower (10.5% vs. 14.4%), among the non-obese subjects with >= 3 metabolic factors than the obese subjects with >= 3 metabolic factors after 11 years. The adjusted relative risk (RR) (95% confidence interval) of renal dysfunction was 1.54 (1.34-1.77) and 1.67 (1.35-2.07) for the obese and non-obese subjects with >= 3 metabolic factors, respectively. Conclusion Non-obese subjects with >= 3 metabolic factors, who are missed based on the essential criterion of obesity for metabolic syndrome, may have an equal or slightly higher risk of renal dysfunction than obese subjects with >= 3 metabolic factors.