Secular trends in the association between nativity/length of US residence with body mass index and waist circumference among Mexican-Americans, 1988-2008

Objectives: We investigated whether associations between nativity/length of US residence and body mass index (BMI) and waist circumference (WC) varied over the past two decades. Methods: Mexican-Americans aged 20-64 years from the National Health and Nutrition Survey (NHANES) III (1988-1994), and NHANES (1999-2008). Sex-stratified multivariable linear regression models further adjusted for age, education, and NHANES period. Results: We found no evidence of secular variation in the nativity/length of US residence gradient for men or women. Foreign-born Mexican-Americans, irrespective of residence length, had lower mean BMI and WC than their US-born counterparts. However among women, education modified secular trends in nativity differentials: notably, in less-educated women, nativity gradients widened over time due to alarming increases in BMI among the US-born and little increase in the foreign-born. Conclusions: Associations between nativity/length of US residence and BMI/WC did not vary over this 20-year period, but we noted important modifications by education in women. Understanding these trends is important for identifying vulnerable subpopulations among Mexican-Americans and for the development of effective health promotion strategies in this fast-growing segment of the population.