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 45-64 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 0.92-0.98, P<0.01, per 5-year increase), Greece (0.90, 0.86-0.94, P<0.01), Italy (0.94, 0.91-0.97, 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.