Cancer incidence in non-immigrants and immigrants in Norway

Major cancers are associated with lifestyle, and previous studies have found that the non-immigrant populations in the Nordic countries have higher incidence rates of most cancers than the immigrant populations. However, rates are changing worldwide – so these differences may disappear with time. Here we present recent cancer incidence rates among immigrant and non-immigrant men and women in Norway and investigate whether previous differences still exist. We took advantage of a recent change in the Norwegian Cancer Registry regulations that allow for the registry to have information on country of birth. The number of person years for 2014–2018 was aggregated for every combination of sex, five-year age-group and country of birth, by summing up each year’s population in these groups. The number of cancer cases was then counted for the same groups, and age-standardised incidence rates calculated by weighing the age-specific incidence rates by the Nordic and World standard populations. Further, we calculated incidence rate ratios using the non-immigrant population as a reference. Immigrants from Eastern Europe, the Middle East, Africa and Asia had lower incidence of total cancer compared to the non-immigrant population in Norway and immigrants born in the other Nordic or high-income countries. However, some cancers were more common in certain immigrant groups. Asian men and women had threefold the incidence of liver cancer than non-immigrant men and women. Men from the other Nordic countries and from Eastern Europe had higher lung cancer rates than non-immigrant men. National registries should continuously monitor and present cancer incidence stratified on important population subgroups such as country of birth. This can help assess population subgroup specific needs for cancer prevention and treatment, and could eventually help reduce the morbidity and mortality of cancer.

恶性肿瘤与生活方式密切相关。既往研究显示，北欧国家的非移民群体多数癌症的发病率高于移民群体。然而，全球范围内癌症发病率正处于动态变化中，此类群体间的差异或随时间推移逐渐消失。本研究旨在呈现挪威境内移民与非移民男女群体近年的癌症发病率，并探究既往存在的群体差异是否依然存续。本次研究依托挪威癌症登记处近期修订的登记条例——新条例允许登记系统收录研究对象的出生国信息。我们按性别、5岁年龄组与出生国的所有组合，对2014至2018年的人年数进行汇总：即逐年累加上述分组的人口规模。随后统计对应分组的癌症病例数，并以北欧标准人群与世界标准人群为权重，计算年龄标化发病率（age-standardised incidence rate）。此外，本研究以非移民群体为参照组，计算了发病率比（incidence rate ratio）。研究结果表明，来自东欧、中东、非洲与亚洲的移民群体，其总体癌症发病率低于挪威境内的非移民群体，同时也低于来自其他北欧国家或高收入国家的移民群体。但部分癌症在特定移民群体中呈现更高的发病风险：亚洲男女群体的肝癌发病率为非移民群体的3倍；来自其他北欧国家与东欧的男性群体，其肺癌发病率高于非移民男性。国家癌症登记机构应持续开展监测，并按出生国等重要人口亚组分层呈现癌症发病率数据。此举有助于评估不同人口亚组在癌症预防与治疗方面的特异性需求，最终助力降低癌症的发病与死亡负担。