Body mass index and annual estimated GFR decline in Chinese adults with normal renal function

The objective of this study was to examine the association between body mass index (BMI) and the annual estimated glomerular filtration rate (eGFR) decline in a rural lean Chinese cohort. A total of 2696 subjects with an eGFR ⩾60 ml/min per 1.73 m2 were followed up for 7 years. Our primary outcome was annual eGFR decline, calculated as (eGFR at baseline−eGFR at revisit)/years of follow-up. During the 7-year follow-up, the mean (s.d.) of annual eGFR decline was 1.7 (1.9) ml/min per 1.73 m2 per year. Compared with subjects with normal weight (BMI 19–22.9 kg/m2), overweight subjects (BMI 23–26.9 kg/m2) had a more rapid annual eGFR decline (β, 0.33; 95% confidence interval (0.18–0.47) ml/min per 1.73 m2 per year), whereas no significant difference was found when comparing the underweight (<19 kg/m2) and the obese (⩾27 kg/m2) groups with the normal-weight group. Moreover, in the 19- to 26.9-kg/m2 range, BMI was positively linearly associated with annual eGFR decline (β2, 0.09 (0.05 to 0.12) ml/min per 1.73 m2 per year, P<0.001), whereas in the <19 (β1, −0.21(−0.45–0.02), P=0.073; β2 versus β1: P=0.009) and ⩾27 kg/m2 (β3, −0.24 (−0.48–0.00), P=0.053; β3 versus β2: P=0.010) range a negative but statistically insignificant trend of association was detected. Our results suggested a nonlinear S-shaped association between BMI and annual eGFR decline among Chinese adults with normal renal function.