All-cause and cause-specific mortality of different migrant populations in Europe

We used data from the MEHO project. Full details on the data acquisition of this project have been reported elsewhere [4].

We obtained all-cause and cause-specific mortality data by country of birth, sex, and age. Data were drawn from six European countries: Denmark, England & Wales (E&W), France, Netherlands, Scotland, and Spain. For Denmark and the Netherlands, data was derived using linkages between records of the population register and subsequent mortality data. Since an open cohort design was used, participants could enter and exit the study at any point in time during the follow-up period. For E&W, France, Scotland, and Spain, unlinked data was used. We derived numbers of deaths by country of birth, sex, and age from the national mortality registers, and calculated the corresponding person-years at risk (PYR) using population census information. Time periods of data collection varied across countries of destination (see Table 1). Data was anonymised, so no ethical approval was needed.

All-cause mortality data was defined as death from any cause. Depending on the country of destination, we employed either the 9th or 10th revision of International Classification of Diseases (ICD). For main causes of death, we included only the causes that constituted at least 1 % of the total deaths in the majority of the migrant populations (see Online Resource 1 for the prevalence rates of the causes of death by region of birth). We chose the following major groupings (ICD codes in brackets): infectious diseases (ICD-9 279.5, 001–139; ICD-10 B20–B24, A00–B99), cancer (ICD-9 140–239; ICD-10 C00–D48), cardiovascular diseases (CVD) (ICD-9 390–459; ICD-10 I00–I99), diabetes (ICD-9 250; ICD-10 E10–E14), and injuries (ICD-9 E800–999; ICD-10 V01–Y98). Given the expected heterogeneity within these groupings, we examined specific causes of death within the cancer and injuries, and infectious diseases groupings. Specific causes of deaths within CVD have been studied earlier [4, 5, 8]. We examined the following causes of cancer mortality (ICD codes in brackets): oesophagus and oral cavity (ICD-9 140–150; ICD-10 C00–C15), stomach (ICD-9 151; ICD-10 C16), colon/rectum (ICD-9 153–154; ICD-10 C18–C21), liver (ICD-9 155; ICD-10 C22.0–C22.1), breast (ICD-9 174–175; ICD-10 C50), Hodgkin’s disease and leukaemia (ICD-9 201, 204–208; ICD-10 C81, C91–95), and lung and bronchus (ICD-9 161–163, 165; ICD-10 C30–34, C39). For injury-related mortality, the following causes were assessed: unintentional injuries (ICD-9 E800–E915; ICD-10 V01–V99, W00–X59), suicide (ICD-9 E950–959; ICD-10 X60–X84, Y87.0), and homicide (ICD-9 E960–E969; ICD-10 X85–Y09, Y87.1). For infectious diseases, we assessed TB (ICD-9 279.5 and HIV/AIDS (B20–B24).

We focused on migrant populations originating from outside Western Europe and the OECD countries. Given the different migration and colonial history, the size of populations by country of birth differed across European countries. Hence, we categorized the migrant populations into larger geographical regions of birth, to make the findings comparable across countries. This classification was based on the Global Burden of Diseases 2010 study [9]. The following region-of-origin groupings were included: North-Africa, Sub-Saharan Africa, the Caribbean, Other Latin America, South Asia, East Asia, Eastern Europe, and Turkey. Since Turkey cannot be easily confined to a particular region (due to its geographical location and historical links with Europe), it was not included as part of a larger regional grouping but was analysed separately. The local-born population of each European country was also included. Region-of-origin groupings with very few deaths and a relatively low PYR (<3000) were excluded from analysis.

Age was categorized into five-year age groups. We restricted the analysis to those aged 0–69 years because there were very few deaths at age 70+ years for most migrant populations. In the linked data (i.e., longitudinal), the age of participants was recorded at baseline, and participants were followed for the duration of the study, irrespective of their age at baseline. Hence, the participants were not censored according to age. In the unlinked data (i.e., cross-sectional), age was recorded in the mortality registry as the age of death; all deaths among people of 70+ years were excluded.

We calculated the age-standardized mortality rates (ASMR) based on direct standardisation using the WHO World Standard Population [10].

We first used sex-specific models to assess differences in all-cause mortality in six European countries combined. We then stratified the analyses by age group (0–19, 20–44, and 45–69), country of destination, and main causes of death. However, because of small numbers of deaths for some populations, cause-specific models were not stratified by sex. We used IBM SPSS version 21.0 for analysis.

In Table 3 age-specific analyses are presented for different migrant populations, compared with local-born populations of the same age group. Those from North Africa, South Asia, and Turkey had higher all-cause mortality in the age group 0–19 years, in contrast to the other age groups. Specifically, those from South Asia mortality had higher in the age group 0–19 years but lower in the other age groups. For women from Sub-Saharan Africa, all-cause mortality was higher in all age groups, while for men mortality was more or less similar in all age groups. Those from Eastern Europe (especially men) had higher mortality in the age groups 20–44 and less so in 45–69 years, with no differences in the youngest age group.

Compared to the local-born populations, the mortality pattern in different migrant populations varied by country of destination. For men, Eastern Europeans had higher mortality in all European countries. South Asian men had higher mortality in Denmark, similar in E&W, and lower in France and Scotland (Fig. 1). For women, those from North Africa tended to have higher mortality in Spain, Scotland and E&W, similar in Denmark, and lower in the Netherlands and France (Fig. 2). East Asian women had lower mortality in Spain, Scotland and France, and similar in Denmark.

Cause-specific analyses are shown in Table 4 (see also Supplementary Material), combined for men and women and for six countries. Compared to local-born populations, mortality due to infectious diseases was higher for most migrant populations, but similar for those from East Asia, Eastern Europe and Turkey. The most important causes were TB and HIV/AIDS, with variations between migrant populations. Cancer mortality was generally lower for the migrant populations, but the pattern varied by cancer site. Mortality due to oesophagus/oral cavity, colon/rectum, and lung/bronchus cancer was lower in the migrant populations. Liver cancer mortality was higher for those from North Africa, Sub-Saharan Africa, and especially East Asia. Mortality due to stomach cancer was higher among those from North Africa, Caribbean, Eastern Europe and Turkey. CVD and diabetes mortality tended be higher for most migrant populations, but consistently lower for those from East Asia and Other Latin America. For injury-related mortality a contrasting picture emerged: for most migrant populations suicide was lower, while homicide was higher.