Evidence of divergence with duration of residence in circulatory disease mortality in migrants to Australia

Background: Very little is known about how acculturation affects health in different societal settings. Using duration of residence, this study investigates acculturation and circulatory disease mortality among migrants in Australia. Methods: Data from death records, 1998-2002, and from 2001 Census data were extracted for seven migrant groups [New Zealand; United Kingdom (UK)/Ireland; Germany; Greece; Italy; China/Singapore/Malaysia/Vietnam (East Asia); and India/Sri Lanka (South Asia)] aged 4564 years. Poisson regression models were fitted to estimate the duration of residence effect (categorized in 5-year bands and also as having arrived 2-16, 17-31 and 32 years ago or more), adjusted for sex, 5-year age group and year of death, then additionally for occupational class and marital status (SES) on relative risks (RR) of CVD mortality. Results: Compared with the Australia-born population, CVD mortality was generally lower in each migrant group. Decreasing mortality with increasing duration of residence was observed for migrants from New Zealand (RR 0.95, 95 Confidence Interval 0.920.98, P < 0.01, per 5-year increase), Greece (0.90, 0.860.94, P < 0.01), Italy (0.94, 0.9-10.97, P < 0.01) and South Asia (0.95, 0.91-0.99, P < 0.01), mainly in older age groups. Trends remained after SES adjustment and also when broader categories of duration of residence were used. CVD mortality among migrants from the UK/Ireland appeared to converge towards those of the Australian-born. Conclusions: These results show divergence in CVD mortality compared with the Australian rate for New Zealanders, Greeks, Italians and South Asians. Sustained cardio-protective behavioural practices in the Australian setting is a potential explanation.