Family migration and physical growth in Merida, Yucatan, Mexico

Merida city in Yucatan, Mexico, has received rural-to-urban migration for decades, with most immigrants settling in the city's southern neighborhoods. Exposure of immigrants to new environmental and sociocultural conditions can generate biological responses, including changes in physical growth pattern at early age. We performed a study to identify and measure the effects of family migration into south Merida on growth in 4- to 6-year-old children, measuring weight, height, sitting height, and calculated arm muscle and fat areas of 445 children: 228 natives (116 females) and 217 immigrants (118 females) and collecting family social and demographic data. Statistical analysis focused on determining differences in growth, socioeconomic, and biological variables by migratory condition and generating multiple regression models for each growth measurement. No univariate statistical differences (P > 0.05, Student's t-test) were observed in growth between studied children. Multiple regression analyses showed age, sex, mother's height, birth order, birth weight, family income, zone of residence, diet, and febrile episodes had an effect on growth. Neither the migration variable used above nor any other definition of migrant had a significant effect on growth. The lack of differences in growth between immigrant and native children is probably due to similarity in socioeconomic conditions of their families.