Influence of internal migration on body mass index: Results of the ELSA-Brasil study.

Objectives To investigate the association between internal migration and body mass index (BMI) in the adult population with data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) and to determine whether the association differs by the urban hierarchical levels (or influence regions) of Brazilian municipalities. Methods Baseline data from 13 084 participants aged 35 to 74 (2008-2010) in the ELSA-Brasil were analyzed. A migrant was defined as an individual whose municipality of residence at the beginning of schooling (origin) was different from the municipality of residence at the study baseline (destination). The origin and destination municipalities were classified by urban hierarchical levels, or influence regions, and migration was categorized as nonmigrant, stable migrant, downward migrant, or upward migrant. Results Of the ELSA-Brasil participants, 51% were migrants. Using gamma regression models, it was observed that for women and men, upward migration was associated with lower mean BMI after adjusting for age, mother's education level, participant's education level, and income. Downward migration, on the other hand, was associated with the highest mean BMI, but this result was statistically significant only for women. Conclusion These findings highlight the role of environmental factors on nutritional status, noting that the effects on BMI may be positive or negative, depending on the trajectory of displacements between origin and destination.