Koffer

1.4.2009 | Von:
Oliver Razum and Jacob Spallek

Explaining The Relationship Between Migration and Health

Studies of the connection between migration and health are often unsatisfactory because of the lack of explicitly-formulated explanatory models. [1] Determinants of disease and health in male and female migrants frequently go unmentioned, making systematic study more difficult.
Die Bulgaren Sevdalin und seine schwangere Frau Julia kommen am 11.06.2013 zu der Station der Malteser Migranten Medizin in Berlin.Patients at a walk-in clinic for illegal migrants in Berlin. (© picture-alliance/dpa)

Even in the field of epidemiology, interest in including migrants in epidemiological studies has awoken only in recent years. [2] Then, when– and this is no rare occurrence – data on the health of migrants does not meet expectations, the search for possible explanations begins retrospectively. It often, and sometimes hastily, ends with the conclusion that there must have been a distortion or an artefact (in other words an ultimately false result arising from problems in the data or errors in their evaluation).

The "healthy migrant" phenomenon

Compared with the majority population, many migrants are socially and economically disadvantaged, and for that reason it might be expected that their health should also be measurably worse. Social epidemiology tells us that a lower socio-economic status raises the risk of disease and premature death. Adult migrants from many countries of origin who migrate to European countries or the USA, however, present lower mortality figures than the non-migrant majority population in the host countries. In some age groups their mortality can be up to 50% lower than in the majority population. [3] The Table shows examples from international literature.

Mortality of migrants relative to the population in the destination country
OriginDestination countryData sourceMeasureRelative risk
Men - Women
Reference
ChinaCanadaCanadian Mortality DatabaseRR0,55 - 0,63Sheth et al. 1999
MexicoUSANational Longitudinal Mortality StudyHR0,57 - 0,60Abraido-Lanza et al. 1999
VietnamEnglandNational Health Service RegisterSMR0,64 - 0,56Swerdlow 1991
Southern Europe*GermanyGerman Socio-Economic Panel (SOEP)RR0,68Razum et al. 2006
Former. USSR**Germany (North Rhine-Westphalia)Population and cause of death statisticsSMR0,89 - 0,81Ronellenfitsch et al. 2006
esp. Latin America, AsiaUSANational mortality dataRR0,77 - 0,84Singh & Hiatt 2006
*"Guest worker"-recruitment countries in the Mediterranean area(Turkey, Yugoslavia, Italy, Spain, Portugal); men and women combined
**Ethnic Germans (Aussiedler/Spätaussiedler)
RR: Relative Risk; HR: Hazard Ratio; SMR: Standardised Mortality Ratio. These measures indicate the mortality of migrants relative to the population of the destination country.
Example: RR = 0,55: male Chinese immigrants in Canada have a mortality factor of 0.55 in relation to Canadian males. This equates to a lower mortality (calculated as 100 - 0,55 x 100).
Source: Razum (2006)

This migrant mortality advantage observed in many data records is referred to in literature as the "healthy migrant effect", or the "phenomenon of the healthy migrant". It is unlikely that this is solely a selection effect among migrants. It is true that migrants are often especially healthy people. However, their health advantage should be apparent in relation to the population of the country from which they originate and not necessarily in relation to the population of the country to which they have migrated. In addition, the advantage is often still apparent years after migration, despite the unfavourable socio-economic conditions under which migrants often live. In view of the inverse association between socio-economic status and mortality, the healthy migrant effect represents a paradox. [4]

Distortions

Artefacts or distortions in the available data are repeatedly cited as explanations for the apparent health advantages or lower mortality of migrants. [5] Deaths among migrants abroad (for example during trips to their country of origin) are not registered in German cause of death statistics. [6] Furthermore, migrants might have returned to their country of origin without giving notice in Germany of their departure; computers would therefore still show them as remaining within the migrant population, thereby "watering down" the observed mortality. Certainly such distortions partly contribute to explaining the differences. It is, however, striking that migrant mortality advantages also exist in studies that can exclude such distortions. [7] Some health advantages also continue to exist after statistical adjustment, even if to a significantly lesser degree than previously. [8]

Social support

Better "social support" among the migrant population than the majority population [9] could also explain part of the health advantages of migrants. This is accounted for by a salutogenetic, i.e. health-promoting effect of social support. However, what contribution it actually makes to explaining health inequality still remains largely unexplained. [10] "Better social support" is therefore mostly just an ad-hoc explanation for apparently paradoxical findings. The underlying consideration is, however, still important: any explanatory model on the health of migrants must not only stress factors that cause poorer health, but must also include health resources and protective factors specific to migrants. [11]

Fußnoten

1.
See Schenk (2007).
2.
See Zeeb and Razum (2006).
3.
See Razum (2006); Razum and Twardella (2002); Singh and Hiatt (2006); Swerdlow (1991); Abraido-Lanza et al. (1999).
4.
See Razum (2006).
5.
See Ringbäck et al. (1999); Kibele et al. (2008); Raymond et al. (1996).
6.
See Neumann (1991).
7.
See Swerdlow (1991); Abraido-Lanza (1999).
8.
See Lechner and Mielck (1998).
9.
See White (1997).
10.
See Mielck (2005).
11.
See Schenk (2007).

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