Primary care utilisation patterns among an urban immigrant population in the Spanish National Health System

Background: There is evidence suggesting that the use of health services is lower among immigrants after adjusting for age and sex. This study takes a step forward to compare primary care (PC) utilisation patterns between immigrants and the native population with regard to their morbidity burden. Methods: This retrospective, observational study looked at 69,067 individuals representing the entire population assigned to three urban PC centres in the city of Zaragoza (Aragon, Spain). Poisson models were applied to determine the number of annual PC consultations per individual based on immigration status. All models were first adjusted for age and sex and then for age, sex and case mix (ACG System (R)). Results: The age and sex adjusted mean number of total annual consultations was lower among the immigrant population (children: IRR = 0.79, p < 0.05; adults: IRR = 0.73, p < 0.05). After adjusting for morbidity burden, this difference decreased among children (IRR = 0.94, p < 0.05) and disappeared among adults (IRR = 1.00). Further analysis considering the PC health service and type of visit revealed higher usage of routine diagnostic tests among immigrant children (IRR = 1.77, p < 0.05) and a higher usage of emergency services among the immigrant adult population (IRR = 1.2, p < 0.05) after adjusting for age, sex and case mix. Conclusions: Although immigrants make lower use of PC services than the native population after adjusting the consultation rate for age and sex, these differences decrease significantly when considering their morbidity burden. These results reinforce the 'healthy migration effect' and discount the existence of differences in PC utilisation patterns between the immigrant and native populations in Spain.