Large multi-centre study finds few differences between mortality in migrant and native populations in western Europe

Mortality in migrants living with HIV in western Europe (1997-2013): a collaborative cohort study.

Migrants Working Group on behalf of COHERE in EuroCoord. Lancet HIV. 2015 Dec;2(12):e540-9. doi: 10.1016/S2352-3018(15)00203-9. Epub 2015 Nov 18.

Background: Many migrants face adverse socioeconomic conditions and barriers to health services that can impair timely HIV diagnosis and access to life-saving treatments. We aimed to assess the differences in overall mortality by geographical origin in HIV-positive men and women using data from COHERE, a large European collaboration of HIV cohorts from 1997 to 2013.

Methods: In this observational cohort study, we included HIV-positive, antiretroviral-naive people accessing care in western Europe from COHERE. Individuals were eligible if enrolled in a cohort that collected information on geographical origin or ethnic origin from Jan 1, 1997, to March 19, 2013, aged 18-75 years, they had available information about sex, they were not infected perinatally or after the receipt of clotting factor concentrates, and were naive to combination antiretroviral therapy at cohort entry. Migrants' origins were grouped into seven regions: western Europe and similar countries (Australia, Canada, New Zealand, and the USA); eastern Europe; North Africa and the Middle East; sub-Saharan Africa; Latin America; the Caribbean; and Asia and the rest of Oceania (excluding Australia and New Zealand). Crude and adjusted mortality rate ratios were calculated by use of Poisson regression stratified by sex, comparing each group with the native population. Multiple imputation with chained equations was used to account for missing values.

Findings: Between Oct 25, 1979, and March 19, 2013, we recruited 279 659 individuals to the COHERE collaboration in EuroCoord. Of these 123 344 men and 45 877 women met the inclusion criteria. Our data suggested effect modification by transmission route (pinteraction=0.12 for men; pinteraction=0.002 for women). No significant difference in mortality was identified by geographical origin in men who have sex with men. In heterosexual populations, most migrant men had mortality lower than or equal to that of native men, whereas no group of migrant women had mortality lower than that in native women. High mortality was identified in heterosexual men from Latin America (rate ratio [RR] 1.46, 95% CI 1.00-2.12, p=0.049) and heterosexual women from the Caribbean (1.48, 1.29-1.70, p<0.0001). Compared with that in the native population, mortality in injecting drug users was similar or low for all migrant groups.

Interpretation: Characteristics of and risks faced by migrant populations with HIV differ for men and women and for populations infected heterosexually, by sex between men, or by injecting drug use. Further research is needed to understand how inequalities are generated and maintained for the groups with higher mortality identified in this study.

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Editor’s notes: This topical analysis on migrant health from the large COHERE collaboration examined mortality in people living with HIV who are treatment-naïve and enrolling for care in 11 western European countries. Routinely collected data were analysed to explore differences in mortality by region of origin. Overall, few differences in mortality were seen between migrant and native populations, with a general trend of similar or lower mortality among migrants than native populations.  However, diversity within migrant groups even from the same region makes it challenging to interpret summary data. The authors provide interesting insights into these difficulties. For example, the reasons for migration are likely to result in different socio-economic conditions in the host country, but heterogeneity in mortality between sub-groups may be masked when looking at overall mortality in migrants compared with the native population. The authors discuss both the “healthy migrant effect” (the fact that it is often healthier, younger populations who are able to migrate), and the “salmon bias” (the fact people who are ill often return to their place of origin). Both of these effects can lead to an observed lower disease burden in migrants than native populations. At a time when immigration is a hotly debated issue in western Europe this study highlights the challenges in assessing migrant health and the need for further empirical and methodological research in this area.

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