Association between length of residence and overweight among adult immigrants in Portugal: a nationwide cross-sectional study

Background: Despite the importance of immigrant population in Portugal few studies have analyzed the patterns of overweight/obesity in this subpopulation. The aims of this study are: (i) describe and compare the prevalence of overweight between immigrants and natives in Portugal; (ii) analyze the association between length of residence and overweight among adult immigrants in Portugal. Methods: A cross-sectional study (2005-2006) in a representative sample of the Portuguese population from national territory, including the Autonomous Regions of Azores and Madeira. The final sample comprised 31,685 adult participants (≥19 years old), of whom 4.6% were immigrants. Country of birth was used to determine immigrant condition. Logistic regressions were conducted to investigate the association between overweight (dependent variable) and length of residence (exposure), adjusting for all covariates in the study. A 5% confidence level and 95% CI were considered. Results: The percentage of immigrants that are overweight [44.9% (95% CI: 42.3; 47.5)] was lower than for natives [52.8% (95% CI: 52.2; 53.4)]. The migrant condition, after adjusted for sociodemographic variables, was not associated with overweight [OR 1.004 (95% CI: 0.998; 1.010)]. Among immigrants, being women [OR 0.585 (95% CI: 0.583; 0.587)], not married [OR 0.784 (95% CI: 0.781; 0.787)] and with a higher education [OR 0.481 (95% CI: 0.478; 0.483)], are probably protective factors of being overweight. Adjusting for other factors, the odds of being overweight for a long-term immigrant (≥15 years) was 1.3 times higher [OR 1.274 (95% CI: 1.250; 1.299)] than for the newcomers (<4 years). Conclusions: The prevalence of overweight was higher for natives than immigrants. Length of residence (≥15 years) was positively associated with prevalence of overweight, among adult immigrant population. In the future, understanding dietary patterns and acculturation process may be important for health immigrant studies.