Increased diabetes incidence in Greek and Italian migrants to Australia: how much can be explained by known risk factors?

Abstract

The aims of the study were to determine whether Greek or Italian migrants to Australia have an elevated incidence of type 2 diabetes compared with Australian-born individuals and to what extent any differences can be explained by known risk factors. This was a prospective study of 34,097 men and women aged 40-69 years born in Greece, Italy, Australia, or New Zealand who were free from diabetes at baseline. For all self-reported cases of diabetes at the 4-year follow-up, a confirmation of diagnosis was sought from medical practitioners. Of these, anyone for whom there was no evidence against a diagnosis of type 2 diabetes was considered a case subject. Follow-up was completed by 29,331 (86%) participants, and 334 case subjects were identified. The cumulative incidence of type 2 diabetes among Greek (2.6%) and Italian (2.4%) migrants was more than three times that in Australian-born (0.7%) individuals. After adjusting for age only, the odds ratios (ORs) for being of Greek and Italian origin compared with Australian origin were 3.8 (95% CI 2.9-5.0) and 3.3 (2.6-4.3), respectively. The only known risk factor for type 2 diabetes that materially affected these ORs was BMI. After adjusting for BMI and age, the ORs for being of Greek and Italian origin, respectively, were 2.4 (1.8-3.2) and 2.0 (1.5-2.6). Greek and Italian migrants to Australia have a more than three times greater incidence of type 2 diabetes than Australian-born individuals, and this is only partly explained by BMI. Although weight control will remain important for these high-risk groups, identification of other risk factors is required.