Sex-specific associations between annual kidney function changes and weight/waist changes in overweight Japanese: Japan Specific Health Checkup cohort.

The impact of changes in obesity-related parameters on kidney functions is unclear. To evaluate the association of body weight (BW) and waist circumference (WC) changes with estimated glomerular filtration rate (eGFR) and proteinuria in obese individuals, we conducted retrospective analysis of the Japan Specific Health Checkup cohort of 664,926 participants (Japanese residents aged 40-74 years) from 2008 to 2011. Participants were classified into nine groups based on BW and WC changes from baseline. Sex differences were stratified. Generalized estimating equations were used to evaluate eGFR changes within each group and the effect of BW or WC changes on eGFR. In a similar manner, the impact of BW and WC changes on the incidence of proteinuria was measured. As a result, total of 20,326 participants with a body mass index of ≥25 kg/m² and available baseline data, 1-year BW and WC, and 4-year eGFR measurements were included in the analysis. The eGFR slope was -0.59 (95% confidence interval [CI], -0.66 to -0.51). At a threshold change of approximately 5%, compared to the group with unchanged BW and WC, males with decreased BW and WC had improved eGFR at 3 years (1.75; 95% CI, 0.49 to 3.02). Contrastingly, females with increased BW and WC had worsened eGFR at 3 years (-3.44; 95% CI, -6.40 to -0.47). These trends were similar when the thresholds were changed or when the outcome was proteinuria. In conclusion, males with decreasing WC and BW had improved kidney function. Future studies should evaluate specific lifestyle factors.