Should I Stay or Should I go? Rural-to-Urban migration and risk of developing Obesity in Peru
Authors: Jose L. Avilez, research trainee at CRONICAS Center of Excellence in Chronic Diseases, UPCH - Rodrigo M. Carrillo-Larco, research trainee at CRONICAS Center of Excellence in Chronic Diseases, UPCH - J. Jaime Miranda, director of CRONICAS Center of Excellence in Chronic Diseases at UPCH
In the late ‘70s and ‘80s, thousands of Peruvian rural dwellers moved to urban cities. Why? Mainly to run away from political violence occurring in rural settings. Many moved to Lima, the capital city, looking for safety, peace and better opportunities. Unfortunately, Lima was not prepared for such a massive internal migration and did not have a proper place for them. This, by itself, serves as a natural experiment to explore the impact of this phenomenon: what is the effect of rural-to-urban migration on health indicators?
Many migrant families had to settle in the surroundings of Lima, soon to become the 4th megacity in the Latin American region, and started a new life as best they could with poor sanitary conditions and facing communicable diseases. Gradually, with improvements in sanitary and socioeconomic conditions the risk of communicable disease falls and non-communicable disease rises: thus accounting for Peru’s epidemiological transition. Therefore, non-communicable diseases and risk factors have become an issue in this population too.
At our CRONICAS Center of Excellence in Chronic Diseases based at Universidad Peruana Cayetano Heredia, we aimed to assess the difference in cardiovascular risk profiles, including high blood pressure, obesity, diabetes, lipids profile, inflammatory markers, metabolic syndrome, and comparing rural and urban subjects, as well as rural-to-urban migrants. This led to a new cross-sectional study in 2007: the PERU MIGRANT study. However, we knew that a single snapshot was not going to tell us enough about cardiovascular risk factors in these three well-defined and yet different population groups. Consequently, we conducted a follow-up round of the same participants in the years 2012-13. Among other questions, we aimed to answer who has higher risk of developing general and central obesity? Since general obesity and central obesity are both associated with mortality, and have different profiles in diverse population groups, it seemed worth studying both in our study population.
Over 95% of participants in the original sample were re-contacted in the same setting where they had been assessed at baseline. This is a strength as newer migration patterns would not affect our question of interest. Compared to rural dwellers, rural-to-urban migrants as well as urban subjects had much higher risk of becoming obese, as per BMI, over 8- and 9-fold higher risk, respectively. This higher risk remained regardless of other associated factors. The size of the effect, that is the magnitude of these relationships, in the case of having a risk of developing central obesity, an indicator captured by measuring the individual’s waist circumference, were much lower than those for obesity status: almost double (actually 95%, close to 100% to make it double) in the rural-to-urban migrant group. The same doubling risk was also noted in the urban subjects, yet our interpretation for this specific group is not conclusive due to the borderline significance obtained.
We also explored if socio-economic indicators, using an assets index and educational attainment, were associated with higher risk of obesity-related markers within each population group. Irrespective of the socioeconomic indicator used, we found no relationship with obesity as captured by BMI. But in terms of central obesity, the assets index, but not educational attainment, was positively related to an increase in the risk —a 45% higher risk among those in the highest asset strata compared with the lowest, i.e., the better off in terms of assets had more risk of developing central obesity no matter the population group: rural, urban, or rural-to-urban migrant. This relationship between economic indicators and the development of obesity has been widely studied and it is, to say the least, an interesting non-static observation. In countries in transition, many of our former “developing countries” can well belong to this category, we observe that as population gains wealth, obesity originally concentrates on the better-off groups, up to a point, and then it “travels and parks” among the poorest groups. When this happens, from a public health perspective, this is too late, as we all know the multiple challenges of improving health among the society’s worse-off. And, to complicate this further, or to make this more fascinating, this observation depends on the indicator being used. For example, whilst having income can push you towards more chances of becoming obese, education can play a protective role. As these observations are not static over time, we have also explored them in different groups of children in Peru and Vietnam, where we call for the implementation of relevant and appropriate obesity prevention strategies alongside improvements in socioeconomic status. In other words, poverty reduction strategies, the so-called lifting people out of poverty, should anticipate mechanisms for not pushing people into obesity.
These results call for newcomers into urban settings to be included in strategies to prevent obesity, and this could be an area to justify such policy recommendations. Why? As we have shown, above, the traditional relationship to describe the risk of developing obesity has been largely based around socioeconomic factors. If we were to tailor our policy by migration categories here is an argument by simply contrasting, side-by-side, the results. First, in terms of developing central obesity, the risk for assets possession was 1.45 versus 1.95 for being a migrant, much higher. Second, in terms of developing obesity, as per BMI, none of the socioeconomic parameters showed higher risk, whereas being migrant had an 8.19 higher risk, eight-fold higher. A word of caution though, to make the comparisons ‘fair’, we need to have the same groups as reference groups, which is not the case, so this comparison is illustrative only, showing the size of the effect.
Obesity acts as a pathway for having several non-communicable diseases, such as cardiovascular disease, which is a leading cause of death across the world. Therefore, obesity prevention is needed if we are to slow down, or even to stop, the increasing incidence of non-communicable diseases and its consequences. Assessment and prevention of obesity, and other risk factors, should be a priority in resource-limited settings where people may not have the opportunity to receive adequate health counselling.
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