[Association of body mass index, waist circumference, and body composition with chronic kidney disease among elderly aged 65 years and above in longevity regions of China].

The prevalence of CKD among elderly participants aged 65 years and above in longevity regions of China was 36.5%.

• Study population included 4,781 participants with mean age (82.8±10.6) years, of whom 2,254 (47.1%) were male.
• CKD was identified in 1,745 cases out of 4,781 participants.
• CKD was defined as eGFR <60 ml·min-1·(1.73 m2)-1 or UACR ≥30 mg/g.
• Data were from the 2021 wave of the Healthy Ageing and Biomarkers Cohort Study (cross-sectional design).

The CKD group had higher age and higher prevalence of hypertension, diabetes, and cognitive impairment compared with the non-CKD group.

• All differences in age and comorbidity prevalence between CKD and non-CKD groups were statistically significant (all P<0.001).
• BMI, waist circumference, muscle mass, and fat mass were all significantly lower in the CKD group compared with the non-CKD group (all P<0.05).

Each 1-standard deviation increase in BMI was associated with a 13.3% higher risk of CKD.

• OR=1.133 (95% CI: 1.053–1.219) per 1-SD increase in BMI.
• Each 1-SD increase in BMI was also associated with a decrease of 1.386 ml·min-1·(1.73 m2)-1 in eGFR (β=-1.386, 95% CI: -1.826 to -0.945).
• Restricted cubic spline analysis revealed a linear positive association between BMI and CKD risk (P for nonlinearity=0.19).
• These associations were derived from multivariable logistic and linear regression models.

Each 1-standard deviation increase in waist circumference was associated with a 12.4% higher risk of CKD.

• OR=1.124 (95% CI: 1.019–1.241) per 1-SD increase in waist circumference.
• Restricted cubic spline analysis revealed a J-shaped positive association between waist circumference and CKD risk (P for nonlinearity=0.016).
• The lowest CKD risk was observed at a waist circumference cut-off value of 79.0 cm.

Each 1-standard deviation increase in muscle mass was associated with an 11.2% higher risk of CKD.

• OR=1.112 (95% CI: 1.006–1.228) per 1-SD increase in muscle mass.
• Each 1-SD increase in muscle mass was associated with a decrease of 1.441 ml·min-1·(1.73 m2)-1 in eGFR (β=-1.441, 95% CI: -2.030 to -0.853).
• Restricted cubic spline analysis showed a linear positive association between muscle mass and CKD risk (P for nonlinearity=0.18).

The associations of BMI and waist circumference with CKD risk differed by sex, being significant only in men.

• In men, BMI was associated with CKD risk: OR=1.218 (95% CI: 1.087–1.365).
• In men, waist circumference was associated with CKD risk: OR=1.215 (95% CI: 1.033–1.433).
• In women, only muscle mass was associated with CKD risk: OR=1.157 (95% CI: 1.035–1.294).
• Neither BMI nor waist circumference showed significant associations with CKD risk in women.

The associations of BMI and waist circumference with CKD risk were significant only in the younger age subgroup (age <80 years).

• In participants aged <80 years, BMI was associated with CKD risk: OR=1.156 (95% CI: 1.020–1.309).
• In participants aged <80 years, waist circumference was associated with CKD risk: OR=1.378 (95% CI: 1.140–1.673).
• These associations were not significant in the older age group (age ≥80 years).