A Body Shape Index and Risk of Kidney Function Decline in Older Adults with CKD

A Body Shape Index has recently emerged as a useful obesity marker for predicting adverse events. Although its usefulness has been reported even in older adults, who tend to exhibit the obesity paradox, little evidence is available regarding the association between A Body Shape Index and kidney outcomes. This study aimed to investigate the associations between A Body Shape Index or body mass index (BMI) and kidney outcomes in older adults with CKD.

This nationwide longitudinal observational study included individuals aged 65-74 years with CKD who underwent annual health checkups between 2008 and 2014. Exposures of interest were A Body Shape Index and BMI, and the primary outcome was a 40% decline in estimated glomerular filtration rate (eGFR). The associations between quartiles (Q1-Q4) of A Body Shape Index and BMI and a 40% decline in eGFR were assessed using Cox regression analysis for each sex. Restricted cubic spline analysis was performed to investigate nonlinear associations. The eGFR trajectory across A Body Shape Index categories was evaluated using a mixed-effects model.

Among 31,292 men and 23,167 women with CKD, 544 men and 315 women experienced a 40% decline in eGFR during a median follow-up of 26.4 months. Compared to Q1 of A Body Shape Index, Q3 and Q4 were associated with the kidney outcome in men, with adjusted hazard ratios and 95% confidence intervals of 1.32 (1.01-1.71) and 1.72 (1.34-2.21), respectively. The rate of eGFR decline over time was also greater in these categories in men. In contrast, the association between high values of A Body Shape Index and kidney outcomes did not reach statistical significance in women. High BMI was not associated with kidney outcomes in either sex.

Higher values of A Body Shape Index were associated with CKD progression in older men in Japan, whereas this association was less evident in women.