Age- and sex-specific associations of underweight and excess adiposity with incident CKD in type 2 diabetes: nationwide Korean cohort study

초록

Background: Obesity is a well-established risk factor for diabetic chronic kidney disease (CKD), but the relationship between body mass index (BMI) and CKD risk remains inconsistent, with paradoxical findings in underweight individuals. These discrepancies may reflect age- and sex-related heterogeneity. Following the Lancet Commission recommendation to integrate adiposity measures, including BMI and waist circumference (WC), we assessed the association between adiposity and incident CKD by age and sex in Korean adults with type 2 diabetes mellitus (T2DM).Methods: Using data from 1,824,317 adults aged ≥40 years with T2DM in the Korean National Health Insurance Service database (2015–2016), excluding those with proteinuria or impaired kidney function, participants were classified by combined BMI and WC as underweight (1.0%), no obesity (59.3%), and excess adiposity (39.6%). Incident CKD was defined by age-adjusted estimated glomerular filtration rate thresholds: new-onset eGFR <60 mL/min/1.73 m2 (age 40-64) and eGFR <45 mL/min/1.73 m2 (age ≥65).Results: During a 4-year follow-up, CKD incidence was 2.8%, 2.3%, and 2.9% across underweight, no obesity, and excess adiposity groups, respectively. Underweight was associated with a substantially greater risk of incident CKD than excess adiposity (OR 1.41, 95% CI 1.29–1.54 vs. OR 1.03, 95% CI 1.01–1.05). Age- and sex-stratified analyses revealed that underweight was associated with increased CKD risk across age and sex groups, particularly in middle-aged men, whereas excess adiposity was associated with increased risk in women but not in men.Conclusions: In Korean adults aged ≥40 years with T2DM, underweight consistently predicted higher CKD risk, particularly in middle-aged men, whereas the association of excess adiposity with CKD differed by age and sex. These findings may help explain previously inconsistent associations between obesity and CKD risk.

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