title: Association between body mass index and diabetic retinopathy in Chinese patients with type 2 diabetes.
abstract: OBJECTIVE
  To explore the factors mediating the relationship between body mass index (BMI) and diabetic retinopathy (DR) in Chinese type 2 diabetes patients.
  
  
  METHODS
  This is a cross-sectional study. Data of 2,533 patients with type 2 diabetes were studied from the Shanghai Diabetes Registry Database. DR was assessed using non-mydriatic fundus photography and graded as non-DR, mild-moderate (DR I-II), and sight-threatening (DR III-IV). BMI (kg/m(2)) was classified as normal weight (18.5 ≤ BMI < 25), overweight (25 ≤ BMI < 30), and obese (BMI ≥ 30). β cell function was evaluated by fasting C-peptide (FCP).
  
  
  RESULTS
  DR was present in 701 (27.7 %) patients. Patients with DR had lower BMI (24.3 vs. 24.9 kg/m(2), P = 0.001) and fasting C-peptide (1.46 vs. 1.86 ng/ml, P < 0.001) than those without DR. The association between BMI (2 kg/m(2) interval) and DR was U-shaped; patients with BMI 28-29.9 kg/m(2) had the lowest DR rate. Compared with normal weight, overweight was associated with reduced risk of any DR [odds ratio (OR) 0.73], DR I-II (OR 0.76), and DR III-IV (OR 0.64) after adjustment for sex, age at diabetes diagnosis, and duration of diabetes. This negative association attenuated after adjustment for other confounders and became nonsignificant after further adjustment for FCP. Patients with different BMI categories had similar DR risk when stratified by FCP tertiles.
  
  
  CONCLUSIONS
  Overweight patients have lower DR prevalence than normal weight individuals, which may be attributable to better β cell function in overweight patients.
authors.affiliation: Department of Endocrinology and Metabolism, Shanghai Diabetes Institute, Shanghai Clinical Center for Diabetes, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, 200233, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.forename: Xuhong
authors.initials: X
authors.lastname: Hou
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Fusong
authors.initials: F
authors.lastname: Jiang
authors.forename: Cheng
authors.initials: C
authors.lastname: Hu
authors.forename: Yuqian
authors.initials: Y
authors.lastname: Bao
authors.forename: Weiping
authors.initials: W
authors.lastname: Jia
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People / Q000706:statistics & numerical data; D015992:Body Mass Index; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000453:epidemiology*; D003930:Diabetic Retinopathy / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology; D050177:Overweight / Q000150:complications / Q000453:epidemiology; D015995:Prevalence