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

BACKGROUND/OBJECTIVES: 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. SUBJECTS/METHODS: A total of 2696 subjects with an eGFR >= 60 ml/min per 1.73 m(2) 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. RESULTS: During the 7-year follow-up, the mean (s.d.) of annual eGFR decline was 1.7 (1.9) ml/min per 1.73 m(2) per year. Compared with subjects with normal weight (BMI 19-22.9 kg/m(2)), overweight subjects (BMI 23-26.9 kg/m(2)) had a more rapid annual eGFR decline (beta, 0.33; 95% confidence interval (0.18-0.47) ml/min per 1.73 m(2) per year), whereas no significant difference was found when comparing the underweight (< 19 kg/m(2)) and the obese (>= 27 kg/m(2)) groups with the normal-weight group. Moreover, in the 19- to 26.9-kg/m(2) range, BMI was positively linearly associated with annual eGFR decline (beta 2, 0.09 (0.05 to 0.12) ml/min per 1.73 m(2) per year, P < 0.001), whereas in the <19 (beta 1, -0.21(-0.45-0.02), P = 0.073; beta 2 versus beta 1: P = 0.009) and >= 27 kg/m(2) (beta 3, -0.24 (-0.48-0.00), P = 0.053; beta 3 versus beta 2: P = 0.010) range a negative but statistically insignificant trend of association was detected. CONCLUSIONS: Our results suggested a nonlinear S-shaped association between BMI and annual eGFR decline among Chinese adults with normal renal function.