Differential effect of body mass index on the incidence of diabetes and diabetic retinopathy in two Asian populations

Aims: To examine the association of body mass index (BMI) with the incidence of diabetes mellitus (DM) and diabetic retinopathy (DR) in Asians. Methods: We analysed data from 4101 adults (Malay, n = 1901 and Indian, n = 2200) who participated in the baseline (2004-2009) and 6-year follow-up (2011-2015) of two independent population-based studies with similar methodology in Singapore. BMI was categorised into normal (< 25 kg/m(2)), overweight (25-29.9 kg/m(2)) and obese (>= 30 kg/m(2)). DM was diagnosed as random plasma glucose >= 200 mg/dL, HbA(1c) >= 6.5% or self-reported physician diagnosed DM. DR was assessed from retinal photographs graded using a standard protocol. The associations of baseline BMI with incident DM and DR was examined using multivariable poisson regression models adjusting for potential confounders including duration of DM, family history of DM and HbA(1c). Results: The incidence of DM was 12.8% and among 1586 participants with DM, the incidence of DR was 17.6% over a median follow-up period of 6.2 years. Compared to those with BMI < 25, the relative risk (95% confidence interval) of incident DM was 1.77 (1.36-2.29) for overweight and 2.01 (1.50-2.71) for obese (p trend < 0.001). Relative risk of DR was 0.80 (0.59-1.09) for overweight and 0.60 (0.39-0.92) for obese (p trend = 0.02). In analyses stratified by ethnicity, similar pattern of associations with DM and DR were observed in both ethnicities. Conclusion: Our results suggest that, overweight and obesity increased the 6-year risk of DM but decreased the 6-year risk of DR in these Asian populations.