The association of diabetes and BMI among Melanesian and Indian Fijians aged ≥40 years

The present study examines the association of diabetes with BMI (kg/m2) in Asian-Indian and Melanesian Fijian populations sharing a common environment. A population-based survey was used to investigate the risk of diabetes (defined by glycosylated Hb concentration ≥6•5% among participants who denied previous diagnosis of the disease by a medical practitioner) by sex, ethnicity and strata of BMI in a series of age-adjusted logistic regression models. Ethnicity and BMI interactions were compared using WHO and empirically derived BMI cut-off points. Indians had a greater risk (BMI and age adjusted) of undetected diabetes than Melanesians in both males (OR 2•99, 95% CI 1•73, 5•17; P<0•001) and females (OR 2•26, 95% CI 1•56, 3•28; P<0•001). BMI ≥25 to <30 and ≥30 kg/m2 conferred a higher risk of diabetes compared with a BMI ≥18•5 to <25 kg/m2. Risk was higher for males with a BMI ≥25 to <30 kg/m2 (OR 2•35, 95% CI 1•24, 4•46; P=0•007) and BMI ≥30 kg/m2 (OR 6•08, 95% CI 3•06, 12•07; P<0•001) than for females with the same BMI (OR 1•85, 95% CI 1•11, 3•08; P=0•027 and OR 2•10, 95% CI 1•28, 3•44; P=0•002, respectively). However, the threshold that appeared to differentiate higher risk varied by ethnicity and sex. For Melanesians, BMI thresholds suggested were 25 kg/m2 for males and 32 kg/m2 for females. For Indo-Fijians, these were 24 and 22 kg/m2 for males and females, respectively. Disaggregating by ethnicity and sex, and applying specific evidence-based thresholds, may render BMI a more discriminating tool for assessing the risk of developing diabetes among Fiji adults.