Ethnic differences in the contribution of insulin action and secretion to type 2 diabetes in immigrants from the Middle East compared to native Swedes

Aims: We investigated insulin action (insulin sensitivity index, ISI) and insulin secretion (oral disposition indices, DIo) and studied metabolic, demographic and lifestyle-related risk factors for type 2 diabetes and insulin action, in the largest non-European immigrant group to Sweden, immigrants from Iraq and native Swedes. Methods: Population-based, cross-sectional study conducted 2010-2012 including residents 30-75 years of age born in Iraq or Sweden, in whom oral glucose tolerance tests were performed and sociodemography and lifestyle behaviors were characterized. Results: In Iraqis compared to Swedes, ISI was more impaired (76.9 vs. 102.3, p < .001) whereas corrected insulin response CIR was higher (226.6 vs. 188.6, p = .016). However, insulin secretion was inadequate given the substantial insulin resistance, as indicated by lower DIo indices in Iraqis than in Swedes (DIo 12,712.9 vs. 14,659.2, p < .001). The crude ethnic difference in ISI was not offset by traditional risk factors like waist circumference, body mass index or family history of diabetes. In Iraqis, ISI conveyed somewhat higher odds of type 2 diabetes than in Swedes (odds ratio OR 0.98, 95% CI 0.97-0.99) vs. OR 0.95, 0.92-0.99), as indicated by an interaction between country of birth and ISI (P-interaction = .044). Conclusion: This study reports ethnic differences in the contribution of insulin action to type 2 diabetes. Our data suggests that the impaired insulin action observed in immigrants from the Middle East to Sweden is not fully explained by established risk factors. (C) 2014 The Authors. Published by Elsevier Ireland Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).