Global Patterns of Mortality in International Migrants: A Systematic Review and Meta-Analysis

Abstract

Background: 258 million people - 3% of the world's adult population - reside outside of their country of birth, yet there has been no previous global systematic review and meta-analysis of mortality data for these international migrants. We undertook a systematic review and meta-analysis to investigate current knowledge about mortality in international migrants. Methods: The review was carried out in line with PRISMA guidelines and was registered on Prospero (CRD42017073608). We searched the MEDLINE, EMBASE, and Global Health databases for studies on international migrants published between 1 Jan 2001 and 31 March 2017. Primary outcomes were standardised mortality ratios (SMRs) and absolute mortality rates. Meta-analyses were conducted using random effects models. Findings: We identified 12480 articles, of which 106 met our inclusion criteria. Data were included from all global regions and for 92 countries. 5498 SMR or absolute mortality estimates on more than 15.2 million migrants were included. The summary estimate of all-cause SMR for international migrants was lower than one (indicating lower mortality) when compared to the general population in host countries to which they migrate 0·70 (95%CI: 0·65-0·76;I2=99·8%). We estimated that all-cause SMR was lower in both male (0·72 [0·63-0·81]; I2=99·8%) and female (0·75 [0·66-0·84]; I2=99·8%) international migrants compared to the host population. The mortality advantage was evident for refugees (0.50 [0.46-0.56];I2=89·8%), but not for asylum seekers (1.05 [0.89-1.24];I2=54·4%), though there were limited data on these groups. SMRs for all causes of mortality were lower in migrants compared to the host population in the destination country with only two exceptions - infectious diseases and external causes - out of 13 ICD-10 categories. Heterogeneity was high across analyses. Point estimates of age-standardised mortality ranged from 488 in women to 874 in men per 100,000 population. Interpretation: Our analyses found that international migrants experience a mortality advantage compared to host populations, and this advantage persisted across the majority of ICD-10 disease categories. This finding is in contrast to the portrayal of migrants as a health burden and demonstrates that international migrants provide a major health benefit for host countries. Our research also highlights the need for better data on underrepresented and potentially more marginalised groups such as asylum seekers and undocumented migrants. Funding Statement: Wellcome Trust, NIHR, MRC, Alliance for Health Policy and Systems Research, DFID, Fogarty International Center, Grand Challenges Canada, International Development Research Center Canada, Inter-American Institute for Global Change Research, National Cancer Institute, National Heart, Lung and Blood Institute, National Institute of Mental Health, Swiss National Science Foundation, World Diabetes Foundation, UK National Institute for Health Research Imperial Biomedical Research Centre and the the Imperial College Healthcare Charity. Declaration of Interests: RWA and IA undertook paid consultancy work in support of the Doctors of the World 2017 Observatory report - Falling through the cracks: The Failure of Universal Healthcare Coverage in Europe. JSF, LBN, and SH have collaborated on research projects with Doctors of the World UK, which includes research commissioned by the Equality and Human Rights Commission on barriers and enablers to care for asylum seekers and refused asylum seekers in the UK. RWA is supported by a Wellcome Trust Clinical Research Career Development Fellowship (206602/Z/17/Z). SB is supported by an NIHR research methods fellowship. JJM acknowledges receiving additional support from the Alliance for Health Policy and Systems Research (HQHSR1206660), DFID/MRC/Wellcome Global Health Trials (MR/M007405/1), Fogarty International Center (R21TW009982, D71TW010877), Grand Challenges Canada (0335-04), International Development Research Center Canada (106887, 108167), Inter-American Institute for Global Change Research (IAI CRN3036), Medical Research Council (MR/P008984/1, MR/P024408/1, MR/P02386X/1), National Cancer Institute (1P20CA217231), National Heart, Lung and Blood Institute (HHSN268200900033C, 5U01HL114180, 1UM1HL134590), National Institute of Mental Health (1U19MH098780), Swiss National Science Foundation (40P740-160366), Wellcome Trust (074833/Z/04/Z, 205177/Z/16/Z) and the World Diabetes Foundation (WDF15-1224). LBN, SH, and JSF receive funding from the UK National Institute for Health Research Imperial Biomedical Research Centre and the Imperial College Healthcare Charity; SH and LN are funded by the Wellcome Trust (Grant number 209993/Z/17/Z) with co-applicants of RWA, JSF and IA for this work. The views expressed are those of the authors and not those of the Wellcome Trust, NIHR, NHS, NHS Research Scotland, Medical Research Council, Chief Scientist’s Office. Ethics Approval Statement: The review was carried out in line with PRISMA guidelines and was registered on Prospero (CRD42017073608).