Objective: Population health surveys have been the main data source for analysis of immigrants' healthstatus in Spain. The aim of this study was to analyze the representation of this population in the SpanishNational Health Survey (SNHS) 2011-2012.Methods: We analyzed methodological publications and data from the SNHS 2011-2012 and the popula-tion registry. Differences in the participation rate between the national and foreign populations and thecauses for these differences were analyzed, as well as the representation of 11 countries of birth in thesurvey with respect to the general population, with and without weighting. Results: Households with any foreign person had a lower participation rate, either due to a higher errorin the sampling frame or to a higher non-response rate. In each country of birth, the sample was smallerthan would be expected according to the population registry, especially among the Chinese population. When we applied the sample weights to the 11 countries of birth, the estimated population volumewas closer to the estimated volume of the population registry for all the countries considered, althoughglobally both the underrepresentation and the intranational bias remained. Conclusions: The lower participation of the immigrant population and differences in participation depen-ding on the country of origin suggest the existence of a potential bias in the SNHS, which should be takeninto account in studies analyzing the health of this population. The lower participation rate should bestudied in greater depth in order to take appropriate measures to increase the representativeness ofhealth surveys. © 2014 SESPAS.

Spain emigrants and immigrants Selection Bias Health surveys

China South and Central America Latin America Europe Consumer Participation selection bias human middle aged statistics and numerical data comparative study Aged Health Surveys ethnology family size consumer Family Characteristics Young Adult Humans migrant Adolescent male Emigrants and Immigrants Spain female Socioeconomic Factors socioeconomics adult Morocco health survey