PurposeTo investigate the associations between body mass index (BMI) with diabetes mellitus (DM) and vision-threatening diabetic retinopathy (VTDR).MethodsThis was a longitudinal study which included DM-free participants aged ≥40 years from the Lingtou Eye Cohort Study at baseline (2008–2010). Physical and ocular examinations were performed at baseline and annual follow-ups under standardised protocol. Two 45° non-mydriatic colour digital retinal photographs were obtained for each eye at all study visits, and presence of VTDR at the 2016 follow-up was graded by a deep-learning algorithm (LableMe) with proved high accuracy for detection of VTDR.ResultsA total of 2934 participants were included with a mean (SD) age of 59.5 (7.3) years (58.3% men). Participants with incident DM (441/2934, 15%) were significantly older (p<0.001), had higher obesity levels (p<0.001), higher systolic blood pressure (SBP) (p<0.001), diastolic blood pressure (p<0.001), fasting plasma glucose (FPG) (p<0.001), triglycerides (p=0.002) and high-density lipoprotein cholesterol (p<0.001), as compared with those without. Participants with incident VTDR (48/2934, 1.63%) were also older (p<0.001), had higher SBP (p=0.013) and FPG (p<0.001), but did not differ in baseline BMI, comparing with those without. Regression analysis showed that higher baseline BMI was significantly related to incident DM (p<0.005), but not incident VTDR, during the follow-up. Subgroup analysis among participants with incident DM also revealed no association between BMI and VTDR.ConclusionsHigher baseline BMI increased the risk of incident DM, but was not related to the risk of VTDR in this adult Chinese population.