Ethnic specific differences in survival of patients with type 2 diabetes: analysis of data collected from an Australian multi-ethnic cohort over a 25 year period.

Aims: To examine the survival of patients with type 2 diabetes from 7 ethnic groups, living in the shared environment of an Australian city.

Methods: Hazard ratio of death (HR) after diagnosis of diabetes was compared between Anglo-Celtic (n=5433), Indigenous Australian (n=439), Pacific Islander (n=354), Mediterranean (n=3138), Arabic (n=768), Indian (n=702) and Chinese (n=1632) patients who live in metropolitan Sydney. Mortality was ascertained by data-linkage with the Australian National Death Index. The modulating effects of glycaemic control, diabetes/vascular complications and risk factors, year of diabetes diagnosis and duration of diabetes on ethnic differences were analysed by Cox regression. Socio-economic status and competence in English were also examined.

Results: There were significant differences in survival between the ethnic groups; the Indigenous Australians had the highest HR for death (2.3, 95% CI 1.7-3.0) and the Chinese the lowest (0.4, 95% CI 0.4-0.5). The survival of the Anglo-Celtics (HR 1) was surprisingly poorer than for Indian (0.6, 95% CI 0.5-0.8), Arab (0.7, 95% CI 0.6-0.8) and Mediterranean groups (0.8, 95% CI 0.7-0.9). Prevalence of smoking and albuminuria were strongly associated with HR. The better survival of Chinese and Arab and the worse survival of Indigenous Australians remained after adjustment of risk factors. Need for an interpreter was a favourable risk factor for survival.

Conclusions: Ethnicity is a significant determinant of survival in type 2 diabetes and this is substantially but not completely mediated by smoking and vascular risk factors. The favourable impact associated with less competence in English may represent a Healthy-migrant effect.