Urolithiasis in immigrant groups: a nationwide cohort study in Sweden

Objective: To study the association between country of birth and incident urolithiasis in immigrant groups in Sweden, using individuals born in Sweden (or with Swedish-born parents in the second-generation study) as referents. Methods: This nationwide follow-up study included first- and second-generation immigrants residing in Sweden between 1 January 1998 and 31 December 2012. Urolithiasis was defined as having at least one registered diagnosis of urolithiasis in the National Patient Register. Cox regression analysis was used to estimate the risk (hazard ratios (HR) with 95% confidence intervals (CI)) of incident urolithiasis. The models were stratified by sex and adjusted for age, sociodemographic status and co-morbidity. Results: Compared to referents, slightly higher incidence rates and HRs of urolithiasis (HR; 95% CI) were observed among first-generation men (1.06; 1.04-1.09) and women (1.12; 1.08-1.16) but not among second-generation immigrants (persons born in Sweden with foreign-born parents). Among first-generation immigrants, higher HRs were noted among men and women from Central and Eastern Europe, Russia, Latin America, Africa and Asia. Lower HRs were seen among men and women from the Nordic countries, most Western European countries and North America. Among second-generation immigrants, higher HRs were noted among men and women from Denmark, Germany and Hungary, in men from Austria, and in women from the Netherlands and Poland. Lower HRs were seen in second generation immigrants from Latin America, Africa and Asia (men and women). Conclusions: We observed substantial differences in incidence of urolithiasis between certain immigrant groups and the Swedish-born population, of importance in the clinical situation.