Longitudinal relationships of metabolic syndrome and obesity with kidney function: Healthy Twin Study

Background: To examine cross-sectional and longitudinal relationships, including genetic and environmental correlations, of metabolic syndrome (MetS) and obesity with kidney function. Methods: Subjects were 3,437 Korean adults of the Healthy Twin Study for cross-sectional relationships and 1,881 participants for longitudinal relationships (follow-up interval 3.7 ± 1.4 years). Obesity (body mass index ≥ 25 vs. <25 kg/m²), MetS, and chronic kidney disease [CKD; estimated glomerular filtration rate (eGFR) (<60 mL/min/1.73 m² using the modification of diet in renal disease study equation)] were categorized at baseline and follow-up. Results: The prevalence and incidence of chronic kidney disease were 2.5 and 3.3 %, respectively. Compared to individuals without obesity and MetS, prevalent CKD was associated with MetS regardless of weight status [adjusted odds ratio (AOR) 4.19 for those with MetS but without obesity; AOR 4.63 for those with MetS and obesity]. Incident CKD was associated with obesity regardless of baseline metabolic status (AOR 2.03 for those with obesity but without MetS; AOR 2.85 for those with obesity and MetS). MetS at follow-up was associated with incident CKD regardless of baseline MetS (AOR 2.42–2.52). Sex-adjusted bivariate analyses show inverse environmental correlations of the number of MetS components and BMI at baseline, with eGFR at baseline and follow-up (ρ_E, −0.26 to −0.42, P < 0.001). Conclusions: MetS predicts prevalent CKD regardless of obesity, and obesity predicts incident CKD regardless of baseline MetS. Incident CKD is also associated with MetS at follow-up regardless of baseline MetS. These associations appear to be explained by shared environmental factors.