African immigrants with type 2 diabetes present with three physiologic subtypes: implications for screening,...

As type 2 diabetes (T2D) prevalence increases in the USA and Africa, factors from both regions affect African immigrants.

T2D in African immigrants was characterized by examining: (a) insulin deficiency and insulin resistance; (b) phenotypic presentation; (c) sociodemographic factors.

In 633 African immigrants (male: 62%, age 39±11, (mean±SD), range 20-70 years), body mass index (BMI): 27.8±4.6, range 18.8-46.2 kg/m²), weight gain information was collected, BMI and waist circumference (WC) measured and OGTT performed. Insulin resistance was defined by the lowest quartile of the Matsuda Index (≤2.80); insulin secretion by the Insulin Secretion Index (ISI). Insulin deficiency was defined as less than the maximum ISI in participants with T2D without IR (0.430). WC thresholds defined central obesity (men: WC ≥94 cm; women ≥80 cm).

Normal glucose tolerance, pre-diabetes and T2D occurred in 61%, 32% and 7%, respectively. Three subtypes of T2D were identified: insulin-deficient-T2D (ID-T2D) in 45%, insulin-resistant-T2D (IR-T2D) in 30%, insulin-deficient+insulin-resistant (ID+IR-T2D) in 25%. ID+IR-T2D had the highest glucose concentrations (all p<0.05), whereas insulins were highest in IR-T2D (all p<0.01). Phenotypic differences by T2D subtype were identified. In the ID-T2D group, 20% of participants had a healthy weight and central obesity occurred in 55%. In the IR-T2D and ID+IR-T2D groups, 100% had central obesity and a BMI in either the overweight or obese categories. Sociodemographic factors specifically, weight gain, sedentary lifestyle and percent married, increased across glucose tolerance category (p values <0.01) but did not differ by T2D subtype (p≥0.3).

Spanning the BMI spectrum from normal to obese, African immigrants have three subtypes of T2D. Weight gain was greatest in immigrants who developed T2D but did not differ by subtype. As life in America promotes weight gain, sharing information about the consequences of weight gain with all Americans, both native and foreign-born, is key to T2D prevention and treatment.