Do cardiometabolic, behavioural and socioeconomic factors explain the 'healthy migrant effect' in the UK? Linked mortality follow-up of South Asians compared with white Europeans in the Newcastle Heart Project.

BACKGROUND: Immigrants are sometimes found to have better health than locally born populations. We examined the mortality experience of South Asian origin and white European origin individuals living in Newcastle upon Tyne, UK.

METHODS: A linked 17-21 year mortality follow-up of a cross-sectional study of European (n=825) and South Asian (n=709) men and women, aged 25-74 years, recruited between 1993 and 1997. Poisson regression was used to estimate mortality rate ratios (MRRs) for all-cause mortality. Sensitivity analysis explored the possible effect of differences between ethnic groups in loss to follow-up. The impact of adjustment for established risk factors on MRRs was studied.

RESULTS: South Asians had lower all-cause age-adjusted and sex-adjusted mortality than Europeans (MRR 0.70; 95% CI 0.58 to 0.85). There was higher loss to follow-up in South Asians. Sensitivity analyses demonstrated that this did not account for the observed lower mortality. Adjustment for cardiometabolic, behavioural and socioeconomic characteristics attenuated but did not eliminate the mortality differences between South Asians and Europeans, although CIs now cross 1 (MRR 0.79; 95% CI 0.55 to 1.13).

CONCLUSIONS: South Asians had lower all-cause mortality compared with European origin individuals living in Newcastle upon Tyne that were not accounted for by incomplete mortality data. It is possible that such migrants to the UK have the resources and motivation to move in search of better opportunities and may be healthier and wealthier than those who remain in their country of origin. These findings challenge us to better understand and measure the factors contributing to their survival advantage.