Do migrants have a mortality advantage?
Authors: Anjali Borhade, Subhojit Dey
Journal: The Lancet (2018)

Internal migration and international migration are both common occurrences with profound implications for both origin and destination geographies and populations. The process of migration and health of migrants are connected in complex ways. An individual's health can influence their decision to move, and migration might affect the health of those who move, those who stay, and even those who host migrants.1Hull D Migration, adaptation, and illness: a review.Soc Sci Med Med Psychol Med Sociol. 1979; 13A: 25-36PubMed Google Scholar, 2WHOHealth of migrants–the way forward. Report of a global consultation. World Health Organization, Geneva2010Google Scholar, 3Lu Y Test of the 'healthy migrant hypothesis': a longitudinal analysis of health selectivity of internal migration in Indonesia.Soc Sci Med. 2008; 67: 1331-1339Crossref PubMed Scopus (138) Google Scholar In host populations, popular rhetoric and media coverage often portray migrants to be in poor health and a burden on health systems.3Lu Y Test of the 'healthy migrant hypothesis': a longitudinal analysis of health selectivity of internal migration in Indonesia.Soc Sci Med. 2008; 67: 1331-1339Crossref PubMed Scopus (138) Google Scholar However, evidence suggests that migrants might be healthier than the general population of host destinations. The so-called healthy migrant hypothesis states that migrants are a healthy group that decide to, benefit from, and succeed in migration, but this advantage might decrease with time.3Lu Y Test of the 'healthy migrant hypothesis': a longitudinal analysis of health selectivity of internal migration in Indonesia.Soc Sci Med. 2008; 67: 1331-1339Crossref PubMed Scopus (138) Google Scholar This situation represents an epidemiological paradox because migrants usually face disadvantages during migration, such as poor living conditions, discrimination, stigma, inequity, and poor social and community support in the host destination, which can negatively impact their health over time. Additionally, according to the so-called salmon bias, migrants generally return to their origin destinations when they are in poor health or before death. This phenomenon has been demonstrated in research studies on internal migrants from Indonesia3Lu Y Test of the 'healthy migrant hypothesis': a longitudinal analysis of health selectivity of internal migration in Indonesia.Soc Sci Med. 2008; 67: 1331-1339Crossref PubMed Scopus (138) Google Scholar and China.4Hesketh T Ye XJ Li L Wang HM Health status and access to health care of migrant workers in China.Public Health Rep. 2008; 123: 189-197Crossref PubMed Scopus (152) Google Scholar In The Lancet, Robert Aldridge and colleagues did a systematic review and meta-analysis5Aldridge RW Nellums LB Bartlett S et al.Global patterns of mortality in international migrants: a systematic review and meta-analysis.Lancet. 2018; (published online Dec 5.)http://dx.doi.org/10.1016/S0140-6736(18)32781-8Summary Full Text Full Text PDF Scopus (118) Google Scholar to investigate current knowledge about mortality in international migrants. The authors compared mortality in international migrants with host populations and investigated differences in mortality by sex, migrant subgroup, and geographical region of origin. Aldridge and colleagues also explored the representativeness of the current evidence base with regard to mortality risk in migrants by investigating the association between cause-specific risk of mortality and the number of studies done by cause-specific International Classification of Diseases, tenth revision (ICD-10) disease category. Analysis of 5464 standardised mortality ratio (SMR) estimates for more than 15·2 million international migrants showed that international migrants had a mortality advantage compared with host populations (SMR 0·7 [95% CI 0·65–0·76]; I2=99·8%). All-cause SMR was lower in both male migrants (0·72 [0·63–0·81]; I2=99·8%) and female migrants (0·75 [0·67–0·84]; I2=99·8%) than the general population. This advantage persisted across most ICD-10 disease categories, with the exception of infectious diseases and external causes. These results are consistent with the healthy migrant hypothesis and the salmon bias. Considering the global scope of the study, this might be one of the most important studies to date to support these hypotheses in migrant populations. These findings also support the epidemiological paradox and indicate that living in poor conditions increases the risk of infectious diseases and death due to external causes (such as assaults and homicide). This paradox might explain the misconception that migrants are carriers of disease and a burden on the health system.6Calderon J Rijks B Aguinas DR Asian labour migrants and health: exploring policy routes. International Organization for Migration, Geneva2012Google Scholar Previous research7Xu Q Guan X Yao F Welfare program participation among rural-to-urban migrant workers in China.Int J Soc Welf. 2010; 20: 10-21Crossref Scopus (71) Google Scholar indicates that most migrants are young and travel when they are healthy. It has also been shown that migrants usually use private health-care services and thus are not a burden on the public health system.3Lu Y Test of the 'healthy migrant hypothesis': a longitudinal analysis of health selectivity of internal migration in Indonesia.Soc Sci Med. 2008; 67: 1331-1339Crossref PubMed Scopus (138) Google Scholar However, the environment in which migrants live and work can increase their risk of infectious diseases. Occupational health hazards are also an issue because of the employment opportunities available for migrants, which often involve work in risky sectors, such as construction and mining with poor regulation and exposure to physical and chemical hazards. In some settings, migrants are also exposed to crime, abuse, and sexual exploitation.6Calderon J Rijks B Aguinas DR Asian labour migrants and health: exploring policy routes. International Organization for Migration, Geneva2012Google Scholar, 8International Labour OrganizationILO multilateral framework on labour migration. International Labour Office, Geneva2006Google Scholar, 9Carballo M Grocutt M Hadzihasanovic A Women and migration: a public health issue.World Health Stat Q. 1996; 49: 158-164PubMed Google Scholar The findings of this study contradict the portrayal of migrants as a health burden for host countries or societies, and highlight the need to improve the affordability and access to safer ways of living, and health care for migrants, which will ensure that their susceptibility to infectious disease and external causes of mortality remains low. Although the study highlights the need for better data on under-represented and marginalised groups, such as asylum seekers and undocumented migrants, there is a clear need to extend this to internal migrants. A few studies done in Indonesia and China support the healthy migrant hypothesis,3Lu Y Test of the 'healthy migrant hypothesis': a longitudinal analysis of health selectivity of internal migration in Indonesia.Soc Sci Med. 2008; 67: 1331-1339Crossref PubMed Scopus (138) Google Scholar, 4Hesketh T Ye XJ Li L Wang HM Health status and access to health care of migrant workers in China.Public Health Rep. 2008; 123: 189-197Crossref PubMed Scopus (152) Google Scholar but the need for further evidence persists, particularly for migrants in low-income and middle-income countries.10Borhade A Dey S Tripathi A Mavalankar D Webster P Migration and health: a review of policies and initiatives in low and middle income countries.Lancet. 2016; 388 (S26 (abstr).)Google Scholar We declare no competing interests. Global patterns of mortality in international migrants: a systematic review and meta-analysisOur study showed that international migrants have a mortality advantage compared with general populations, and that this advantage persisted across the majority of ICD-10 disease categories. The mortality advantage identified will be representative of international migrants in high-income countries who are studying, working, or have joined family members in these countries. However, our results might not reflect the health outcomes of more marginalised groups in low-income and middle-income countries because little data were available for these groups, highlighting an important gap in existing research. Full-Text PDF Open Access