Global Migration and Health Outcomes: Examining a Complex Relationship

The UCL-Lancet Commission on Migration and Health has released data from evidence-based research on global migration and health outcomes, published in the Lancet.

The commission provides data in the interest of “[informing] public discourse and…[addressing] migration as a global health priority.”¹ As part of the commission, 2 literature meta-analyses published in the Lancet examined the mortality trends and health outcomes associated with migration.^2,3 Combined, the results of these analyses indicate that international migrants have a slight mortality advantage compared with general populations, although parental migration may negatively affect “left-behind” youth.³

To examine mortality trends among international migrants, investigators conducted a literature search of MEDLINE, Embase, Cochrane Library, and Google Scholar databases. Selected for inclusion were observational studies, systematic reviews, and randomized controlled trials published between January 1, 2001, and March 31, 2017. Of 12,480 articles identified, 96 were eligible for inclusion.²

The total cohort included 15.2 million migrants with 5464 mortality estimates, among which 97% were from high-income countries, 2% were from middle-income countries, and <1% from low-income countries. The all-cause standardized mortality ratio (SMR) was lower for international migrants compared with the general population (SMR, 0.70; 95% CI, 0.65-0.76), suggesting a slight mortality advantage for migrants. All-cause SMR was lower in both male migrants (SMR, 0.72; 95% CI, 0.63-0.81) and female migrants (SMR, 0.75; 95% CI, 0.67-0.84).

SMRs were lower in migrants compared with the general population in the destination country for all causes of death, with the exception of infectious diseases and external causes. Heterogeneity was high across studies; meta-analysis results must be extrapolated with care. Even so, these data strongly suggest a slight mortality advantage among international migrants over the general population in the destination country.

Beyond the health outcomes of migrants themselves, researchers also assessed the effect on children left behind after parental migration. MEDLINE, Embase, CINAHL, the Cochrane Library, Web of Science, PsychINFO, Global Index Medicus, Scopus, and Popline were searched from inception to April 27, 2017, for observational studies reporting the effects of parental migration on left-behind children (aged 0-19 years) in low- and middle-income countries.

Of the 10,284 studies identified by search criteria, 111 were selected for analysis.^[3] The total study cohort comprised 264,967 youths, among whom 106,167 were “left-behind” and 158,800 were children of nonmigrants. Compared with children of nonmigrants, left-behind children had increased risk for depression (relative risk [RR], 1.52; 95% CI, 1.27-1.82), anxiety (RR, 1.85; 95% CI, 1.36-2.53), suicidal ideation (RR, 1.70; 95% CI, 1.28-2.26), conduct disorder (standardized mean difference, 0.16; 95% CI, 0.04-0.28), substance use (RR, 1.24; 95% CI, 1.00-1.52), wasting (RR, 1.13; 95% CI, 1.02-1.24), and stunting (RR, 1.12; 95% CI, 1.00-1.26). Left-behind children did not differ from non-migrant children on other nutritional outcomes, unintentional injury, abuse, or diarrhea. These data suggest that parental migration has deleterious effects on left-behind children and adolescents.

Per the results of 2 separate literature reviews, global migration has a complex relationship with health outcomes, both for migrants themselves and for their children. Public health professionals should maintain awareness of any negative effects and work to mitigate them in clinical practice. Authors underscored the slight mortality advantage migrants have over the general population as a means of “[reframing] the public discourse on international migration and health.”² Public discourse surrounding migration often stigmatizes migrants as having poorer health outcomes; these data, among other research published by the UCL-Lancet Commission, are working to reverse such perceptions.

References

1. Abubakar I, Aldridge AW, Devakumar D, et al. The UCL–Lancet Commission on Migration and Health: the health of a world on the move. Lancet. 2018;392(10164):2606-2654.
2. Aldridge RW, Nellums LB, Bartlett S, et al. Global patterns of mortality and international migrants: A systematic review and meta-analysis. Lancet. 2018;392(10164):2553-2566.
3. Fellmeth G, Zhao C, Busert LK, et al. Health impacts of parental migration on left-behind children and adolescents: a systematic review and meta-analysis. Lancet. 2018;392(10164):2567-2582.