A Population-Based Retrospective Study Comparing Cancer Mortality Between Moluccan Migrants and the General Dutch Population: Equal Risk 65 Years After Immigration?
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Open access Research BMJ Open: first published as 10.1136/bmjopen-2019-029288 on 15 August 2019. Downloaded from A population-based retrospective study comparing cancer mortality between Moluccan migrants and the general Dutch population: equal risk 65 years after immigration? Junus M. van der Wal, Adee Bodewes, Charles Agyemang, Anton Kunst To cite: van der Wal JM, ABSTRACT Strengths and limitations of this study Bodewes A, Agyemang C, Objective To test the hypothesis that cancer mortality et al. A population-based rates among the Moluccan–Dutch, the oldest non-Western ► This is the first study to investigate cancer mortality retrospective study comparing migrant group to arrive in the Netherlands after the Second cancer mortality between among the Moluccan–Dutch, the oldest non-west- World War, are similar to those in the general Dutch Moluccan migrants and the ern migrant group to enter the Netherlands after the population. general Dutch population: Second World War. Design Population-based retrospective study. equal risk 65 years after ► We employed a novel approach to select persons Setting Data from the national cause of death registry in immigration? BMJ Open from Moluccan descent from the Dutch national the Netherlands and municipal registries. 2019;9:e029288. doi:10.1136/ cause of death registry, by selecting persons based bmjopen-2019-029288 Participants Using historic records containing family on the Moluccan family names registered in histori- names of all Moluccan–Dutch who arrived in the ► Prepublication history for cal immigration documents, which were made avail- Netherlands in 1951, we identified 81 591 Moluccan– this paper is available online. able to us for research purposes. Dutch persons in the national cause of death registry of To view these files please visit ► A limitation of this novel selection method is the fact the Netherlands. The reference group consisted of 15 866 the journal online (http:// dx. doi. the we were unable to identify second-generation 538 persons of the general Dutch population. org/ 10. 1136/ bmjopen- 2019- Moluccan–Dutch persons with a native Dutch father 029288). Outcome measures Mortality data were linked to and consequently Dutch family name. demographic data from municipal registries. We calculated ► Another limitation is the low number of deaths for http://bmjopen.bmj.com/ Received 20 January 2019 all-cancer and cancer-specific mortality and measured most cancer types in the Moluccan–Dutch group, Revised 23 July 2019 differences between the two groups using Poisson Accepted 25 July 2019 limiting statistical power. regression, adjusting for sex, age and area socioeconomic status. We conducted a sub-analysis for the first- generation and second-generation Moluccan–Dutch. is thought to be influenced by differences in Results There was no difference in all-cancer mortality cancer epidemiology between high-income between Moluccan–Dutch and the general Dutch countries (HICs) and LMIC and exposure population. Mortality was higher among Moluccan–Dutch to concordant risk factors.2 When compared for liver, cervix and corpus uteri cancers, but lower on September 27, 2021 by guest. Protected copyright. for stomach, oesophagus, kidney and nervous system with their host population, cancers related to cancers. For most cancers, mortality risk as compared infection, such as liver, stomach and cervical with the general Dutch population varied between different cancer, are more common in migrants from generations of Moluccan–Dutch. LMICs; cancers considered to be related to Conclusions Several decades after migration, the Western lifestyle such as colorectal, breast Moluccan–Dutch show similar all-cancer mortality, but and oesophageal cancer are less common in different cancer-specific mortality rates, when compared these groups.1 with the general Dutch population. Increasing evidence suggests that such © Author(s) (or their epidemiological differences become less employer(s)) 2019. Re-use permitted under CC BY. pronounced as LMIC-migrants reside in their Published by BMJ. INTRODUCTION destination country for a longer period, as Department of Public Health, Ethnic disparities in the prevalence and local (Western) cancer-related risk factors Amsterdam UMC (location mortality burden of different cancer types will eventually predominate over risk factors AMC), University of Amsterdam, are known to exist in Europe.1 For instance, associated with their country of origin.2 Amsterdam, The Netherlands migrants from low-income and middle-in- Moreover, second-generation migrants who Correspondence to come countries (LMIC) tend to show lower were born in HICs lack early life risk factor Junus M. van der Wal; all-cancer mortality and morbidity. More- exposures experienced by the first gener- j. m. vanderwal@ amc. uva. nl over, cancer burden among LMIC-migrants ation, such as possible higher infection van der Wal JM, et al. BMJ Open 2019;9:e029288. doi:10.1136/bmjopen-2019-029288 1 Open access BMJ Open: first published as 10.1136/bmjopen-2019-029288 on 15 August 2019. Downloaded from pressure.3 Accordingly, some studies on LMIC-migrants in the Netherlands are documented by a physician on who have resided in their host country for more than a death certificate form and cause of death is classified one generation have suggested a shift in cancer epide- in accordance with the 10th Revision of the Interna- miology towards rates of the native population of their tional Classification of Diseases (ICD-10), after which it destination country.4–6 In the Netherlands, such a pattern is recorded in the cause of death registry. Demographic has been shown most consistent in Surinamese migrants data were derived from municipal registries and included for mortality caused by most major cancers, but is also date of birth, sex and place of residence. Both registries suggested for migrants from Turkey, Morocco and the include all legal residents in the Netherlands, and are Netherland Antilles.4 6 Given the limited number of linked through personal identification numbers. studies on this topic, more research is necessary to further Moluccan–Dutch persons were identified in the regis- characterise the cancer risk profile in these groups and tries based on surname. Using passenger lists of the address the question to what extent ethnic disparities in various boats that transported Moluccans to the Nether- cancer mortality persist or start to converge to those of lands in 1951, the Museum Maluku Netherlands created the host population. a list containing approximately 1700 surnames of the For this reason, we set out to assess the difference in arriving Moluccan families. This list was used to identify cancer mortality between the general Dutch population and link persons of Moluccan descent in these registries. and the Moluccan–Dutch, the oldest LMIC migrant After identification and linking, data were anonymised. group to settle in the Netherlands after the Second The reference group, referred to as ‘general Dutch World War. The Moluccan–Dutch are a migrant group population’ consisted of 15 866 538 persons with Dutch consisting of the former soldiers from the Royal Neth- nationality. erlands East Indies Army (KNIL), the military force of We used birth year to determine Moluccan generations. the Netherlands in their former colony. These soldiers, We considered people born up to 1951, the year of migra- and their families, were transported to the Netherlands tion, to be of the first generation and people born after in spring 1951 after decolonisation of Indonesia. Even 1951 but before 1970 of the second generation. We chose though their stay was supposed to be temporary, the 1970 as cut-off point and excluded persons born hereafter, majority settled in the Netherlands after their struggle to since Moluccan–Dutch born after this year will increas- found their own republic on the Moluccan Islands failed. ingly be offspring of the second generation (ie, the third No considerable chain or remigration occurred, resulting generation) and because the number of death in this in a closed minority group, the vast majority of which group was low due to relatively young age. Furthermore, resided in segregated Moluccan districts throughout the we created two groups within the first generation, based Netherlands.7 on whether the person was an adult (born before 1934) Earlier studies found differences in cancer standard or a minor (born between 1934 and 1951) in the year that incidence ratios and mortality between migrants from the Moluccan migrants were transported to the Nether- http://bmjopen.bmj.com/ Indonesia and the general Dutch population.8–10 A sepa- lands. We made this stratification, since Moluccan–Dutch rate analysis of the Moluccan–Dutch is desirable, since who migrated to the Netherlands as minor are expected their particular migration history resulted in a homoge- to show distinctly different cancer risk exposures than neous group within the Indonesian community with their both the first-generation adults, who have similar early own cultural practices, lifestyle and migration history, all life exposures from Indonesia but are less integrated in of which can have a profound impact on cancer risk. Dutch society, or the second generation, who lack early The aim of this study was to assess the difference in all life exposures from Indonesia altogether. cancer and cancer-specific mortality rates between the In one analysis, we only included Moluccan–Dutch of on September 27, 2021 by guest. Protected copyright. Moluccan–Dutch and the general Dutch population, with the first and second generations, and we compared them a subanalysis for the first and second generations. Since to their Dutch counterparts born in the same periods. the Moluccan–Dutch have resided in the Netherlands for This reference group included 9 064 169 persons with over 65 years, we expect local environmental factors in Dutch nationality born up to 1970. the Netherlands to reflect on mortality rates, for instance Area-level social economic status (SES) was used as in cancers that are known to be influenced by factors such proxy for individual SES.