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. 1-3 In host populations, popular rhetoric and media coverage often portray migrants to be in poor health and a burden on health systems. 3 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. 3 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 Indonesia 3 and China. 4 In The Lancet, Robert Aldridge and colleagues did a systematic review and meta-analysis 5 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. 6 Previous research 7 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. 3 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. 6,8,9 Published Online December 5, 2018 http://dx.
Borhade, A., & Dey, S. (2018, December 15). Do migrants have a mortality advantage? The Lancet. Lancet Publishing Group. https://doi.org/10.1016/S0140-6736(18)33052-6