Risk of cervical cancer among immigrants by age at immigration and follow-up time in Sweden, from 1968 to 2004.

Because of great variation in the prevalence of human papilloma virus infection and other risk factors of cervical cancer worldwide, migrant studies may help further the understanding of the aetiology and improve prevention of cervical cancer. Our aim was to study the risk of invasive cervical cancer among immigrant women. We followed 758,002 immigrants from different countries who resided in Sweden between 1968 and 2004. Age-standardised incidence rates (ASRs) of immigrants were compared with that in their countries of origin. Poisson regression models estimated the relative risks of cervical cancer among immigrants, overall and stratified by age at migration and follow-up time, compared to Swedish-born women. Overall 1,991 of 19,542 observed cases of cervical cancer occurred among immigrants. Generally they had lower ASRs than in their countries of origin, with the exception of Nordic immigrants. Compared to Swedish-born women, we observed a higher relative risk of cervical cancer among immigrants overall (RR = 1.13, 95% CI 1.08-1.18), and particularly among women from Denmark (RR = 1.8, 95% CI 1.6-2.1), Norway (RR = 1.7, 95% CI 1.5-1.9) and Central America (RR = 2.5, 95% CI 1.3-4.9), while the relative risks were lower in immigrants from Eastern Africa (RR = 0.2, 95% CI 0.1-0.6), South Central Asia (RR = 0.4, 95% CI 0.2-0.6) and South Western Asia (RR = 0.5, 95% CI 0.4-0.7). Follow-up time and age at migration were important effect modifiers for cervical cancer risks. We suggest targeted prevention toward high-risk immigrants, specifically older women, in the first 10 years after arrival into their new homeland.