Using a measure of relative height to capture their underlying health, Alessandro Ferrara, Renee Luthra and Lucinda Platt investigate how the health of immigrants unfolds over time – offering an explanation for the so-called “immigrant health paradox”.
Those who move abroad for a better life tend to differ in systematic ways from those who stay in their country of origin. We know, for example, that those who migrate are more highly educated on average than those who do not; and it is often stated that migrants are healthier than non-emigrants.
This makes sense: it is harder to migrate if you are sick, and less healthy individuals are less likely to reap the economic benefits of migration. But comparisons with those in the countries they move to suggest that, while immigrants start off healthier, they lose that health advantage over time. These two facts taken together – immigrants having better health to start with, but facing declining health over time – are often referred to as the immigrant health paradox.
In a recently published discussion paper, we aimed to examine whether those who migrate are indeed healthier than those who do not and whether those who are healthier at migration experience the same health decline as those who are less so.
Height as a proxy for underlying health
To answer these questions, we examined the health status and outcomes of a nationally representative sample of immigrants from a range of origin countries in Germany. We based our understanding of health at migration on immigrants’ height relative to the average for their birth cohort and sex in their origin country. Population height tends to increase with affluence, and someone’s height compared to their compatriots derives both from their genetic inheritance but also, crucially, from their exposure to poor/good nutrition and any ill-health in utero and childhood. Those who end up taller are therefore healthier, on average, than those who end up smaller. Height is also stable between around 18 and 50, and is thus unaffected by migration.
Those who end up taller are healthier, on average, than those who end up smaller
Accordingly, we first constructed a dataset of heights by birth cohort and sex for many immigrant-sending countries across the world. We then compared these reference heights to those of adult immigrants in the German Socio-Economic Panel (SOEP), which includes a large sample of immigrants. This allowed us to construct a measure of relative height – and therefore underlying health status – for almost all the immigrants in the study.
Inspecting the data, we find that there is a lot of variation in the relative height of immigrants – some have better underlying health than others, though on average emigrants are relatively taller (ie, healthier) than their non-migrating counterparts. The factors that predict who is relatively taller (healthier) among emigrants are those we would expect. As Figure 1 shows, those who are more likely to be migrating directly for economic reasons (male, younger, not refugees) and who face greater barriers to migration (eg, visa conditions due to being non-EU) tend to be relatively taller (healthier).
Figure 1: Factors predicting relative height
We then looked at whether those with better underlying health (relatively taller) had better health according to four measures of current health status: reported subjective health; reported physical health; whether individuals were less likely to report a diagnosed condition; and whether they visited the doctor less often.
We found that those who were relatively taller did have better health outcomes, but these could be accounted for by differences in their demographics and in their educational attainment, characteristics that are also associated with better health. In other words, net of these factors, relative height on its own didn’t imply better health, when measured for all immigrants regardless of length of stay.
Revisiting the immigrant health paradox
To shed light on the immigrant health paradox – that immigrants start off with good health relative to those native-born at destination, but face health deterioration the longer they stay – we consider time since migration and make comparisons between immigrants and native-born residents. We speculated that soon after migration, all immigrants should be relatively healthy, but that the health advantage offered by relative height might play out over time. To test this, we compared the outcomes with native-born Germans for those who were relatively tall (ie, in the top 25 per cent of relative height) and those who were relatively short (bottom 25 per cent) – and looked at how these evolved over time since migration.
We found that closer to the time of migration, both the relatively tall and the relatively short immigrants tended to be healthier than native-born Germans, consistent with the first element of the immigrant health paradox. Over time, however, those with poorer underlying health (relatively shorter) showed deteriorating health relative to native-born Germans, while those who had better underlying health (relatively taller) sustained similar or better health. Thus, the deterioration in health that is the second part of the immigrant health paradox is driven, in fact, by those with poorer underlying health status. This makes intuitive sense.
Over time, it was those with poorer underlying health (relatively shorter) who showed deteriorating health relative to native-born Germans
This is illustrated in Figure 2, where the green line shows those who were relatively shorter, and the red line shows those who were relatively taller. As they spend more time in the country, differences in the underlying health status implied by their relative height are realised. For those with poorer underlying health, they experience worsening subjective and physical health, increases in diagnosed conditions and increases in number of doctor’s visits. The findings are all the more convincing given they are consistent across these four different measures of health status.
Figure 2: Health gap in four health outcomes between the top quartile group and the bottom quartile group of relative height of immigrants and native-born Germans
Our study therefore sheds light on a number of questions in the immigration literature. Using a measure of underlying health that precedes migration, we show that on average migrants are “selected” for their good health, albeit with a lot of variation in that general story. That variation in turn allows us to examine whether those who are inherently healthier have better health trajectories than those who are less so – and we show that they do.
We thus improve understanding of the so-called immigrant health paradox in a way that renders it less paradoxical. We show that it is not those immigrants who are “selected” for their good health who face the observed deterioration in health over time. Rather, we see that it is those whose underlying health status is poorer, even though they may have been outwardly in good health when they migrated, who drive the downward trajectory in health over time since migration. This does not mean that other candidates which have been proposed as affecting migrant’s health over time – the stressful, menial or dangerous nature of jobs or the stress due to discrimination or harassment – do not play a part in affecting migrant health. But it is logical that those who are more vulnerable to poor health will also be more affected by such factors as well as accumulating negative health experiences over time.
We will be able to use our cross-national database of height distributions to explore other immigrant-receiving countries, such as the UK, and ascertain whether in these other countries immigrants are also more likely to have greater relative height and whether those who do show similar retention of their health status. This could help to explain some of the cross-country differences in migrant outcomes, even for those from the same country of origin.
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Are Immigrants Selected on Height? And Does this Bring a Health Premium in the Destination Country? By Alessandro Ferrara, Renee Luthra and Lucinda Platt is available here.
All articles posted on this blog give the views of the author(s). They do not represent the position of LSE Inequalities, nor of the London School of Economics and Political Science.
Image credits: Iron workers (1954) and subway workers (ca. 1910) in New York City courtesy of Everett Collection via Shutterstock.
