Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 https://doi.org/10.1186/s12939-019-0939-9 RESEARCH Open Access Trends in mortality inequalities in an urban area: the influence of immigration Maica Rodríguez-Sanz1,2,3,4, Mercè Gotsens1,2,4, Marc Marí dell’Olmo1,2,3,4 and Carme Borrell1,2,3,4* Abstract Background: Nearly 20% of the population in Barcelona is foreign-born and this percentage rises to up to 40% in some neighborhoods. Consequently, migration health patterns may play an important role in trends in socioeconomic geographical inequalities in mortality. The objective of this study was to analyze the trend in socioeconomic inequalities in mortality between neighborhoods in Barcelona during the period 2001–2012 in the foreign-born and Spanish-born population. Methods: Repeated cross-sectional design of the population aged 25–64 years in Barcelona between 2001 and 2012. Hierarchical data consisted of yearly mortality linked-population. The variables analyzed were age, sex, education, and country of birth (Spanish-born, foreign-born), neighborhood of residence, and the socioeconomic level of the neighborhoods using quartiles of unemployment rates. Age-standardized mortality rates were estimated, and mixed Poisson regressions were applied using generalized linear mixed models, including two random effects to consider the intracorrelation within neighborhoods and across years. Results: The number of foreign-born residents aged 25–64 increased notably in disadvantaged neighborhoods. Approximately 9% of premature deaths occurred in foreign-born individuals. Premature mortality rates were higher in disadvantaged neighborhoods and in the Spanish-born population in all periods. Despite the stabilized socioeconomic inequalities in mortality in the Spanish-born population, no inequalities were found between neighborhoods in foreign-born men and women. Conclusions: Evidence of the ‘healthy migrant’ effect in mortality and socioeconomic inequalities in mortality was found in Barcelona, which seems to alter the distribution of mortality through time and space, related to the low levels of premature mortality and the selective residence of immigrants in socioeconomically disadvantaged neighborhoods. Keywords: Health equity, Epidemiology Introduction increased in most western and central European coun- More than half the world’s population lives in urban tries, although this migration flow decreased after the start areas, reaching 70% in high-income countries. This of the global economic recession in 2008 [4]. In Spain, the trend is increasing mainly because populations migrate migrant population rapidly grew from 4% of the popula- to cities seeking better working and living conditions [1]. tion in 2000 to 12% in 2009 [5], whereas in Barcelona in Nonetheless, cities have certain risks, where social in- 2009 the foreign-born population represented 19% of resi- equalities also exist, as there are socioeconomically dis- dents, with seven out of ten coming from countries such advantaged neighborhoods or areas where the most as those of Latin America, Morocco, China and Pakistan vulnerable populations tend to concentrate, leading to [6, 7]. The growth of immigration is usually unequal poorer health among their residents [2, 3]. across space, with some residential segregation patterns During the 1980s, the foreign-born population rose in being reproduced by selective migration processes that some European countries and, mainly after 2000, it sort immigrants into socioeconomically disadvantaged neighborhoods. This is true of Barcelona, where the center * Correspondence: cborrell@aspb.cat of the city, the starting point for new arrivals, and some 1 Agència de Salut Pública de Barcelona, Lesseps, 1, 08023 Barcelona, Spain 2 Institut d’Investigacio Biomedica (IIB Sant Pau), Barcelona, Spain Full list of author information is available at the end of the article © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 Page 2 of 9 peripheral neighborhoods play host to more than 40% of Data and methods foreign-born residents [6]. This study used repeated cross-sectional data from the Previous research has provided support for the concept of population aged 25–64 years resident in Barcelona be- “migrant selectivity”, as migrants are often, at least initially, tween 2001 and 2012. We studied this group of age in younger and healthier than non-migrants in their host order to include population with education finished countries, a phenomenon known as the “healthy migrant ef- (more than 25 years of age) and taking into account that fect”. In addition, migrants tend to have significantly lower immigrant population is younger than 65 years of age. mortality than persons in their host countries, because im- Moreover, premature mortality, which implies deaths migrants who are ill may return to their native countries for that occur prematurely, usually includes mortality under treatment or to die, a process called “salmon bias” [8]. Stud- 65–70 years of age [29]. The information sources were: ies on migrant mortality in the European context have ex- a) the municipal population register to estimate the amined different issues. Some of them have reported that population at risk, and b) the mortality register of Barce- overall and premature mortality was lower for the lona, which includes geocoded data for each correspond- foreign-born than the local born population, independently ing residential address (99% of deaths) and the of individual socioeconomic characteristics [9, 10]. In educational level of the deceased (93% of deaths) ob- addition, some studies analyzed how this pattern was medi- tained through record linkage with the local population ated by sex, age and country of origin [11–17] and register. depended on the specific cause of death [11, 12, 15–18]. The hierarchical dataset was yearly mortality Few studies have analyzed the association between immi- linked-population using groups of individuals by age, sex, grant mortality and greater length of residence [13, 19, 20]. education (primary or less, secondary, university, unknown), A study has suggested that immigrant mortality may be in- country of birth (Spanish-born, foreign-born), and neigh- fluenced by different integration policy contexts in host borhood of residence. Barcelona was divided into 38 neigh- countries [21]. borhoods where the population varied from 500 to 100,000 On the other hand, some studies have found that popula- inhabitants, approximately, with a median of nearly 35,000 tion growth and selective migration could be responsible residents. The unemployment rate was used to characterize for a change in geographical mortality inequalities between the socioeconomic context of the neighborhoods because it the least and most deprived areas [22]. One study that ana- is a common and simple measure of area-based socioeco- lyzed 250 regions in 26 European countries found that areas nomic context widely used in research on geographical in- with large population gains through migration were more equalities in mortality [30]. Due to the fact that the likely to have low death rates, independently of area socio- distribution of unemployment in the neighborhoods has economic status [23]. Narrowing inequalities have been de- been stable through the years, we used the unemployment scribed in the UK, with less deprived areas experiencing rate of 2001, using quartiles (Q1 low unemployment: population gain and these areas having lower premature 7.6%-9,8%, Q2: 10–10.7%, Q3: 10.7–12.2, Q4 high un- mortality rates, notably in London [24]. In contrast, in employment 12.4–17.2%). France [25], reductions in mortality were found in deprived All analyses were stratified by sex. In addition, to estimate areas showing population growth, related to new residential the effect of migration, all estimates were fitted in the total areas and/or an influx of a wealthier population. In Barce- number of men and women, and separated by country of lona, a recent study found that the reduction in inequalities birth (Spanish- and foreign-born). Three periods were ana- in mortality between neighborhoods was related to an in- lyzed: 2001–2004, 2005–2008 and 2009–2012 (period of crease in the foreign-born population in disadvantaged the financial crisis), and biannual periods were used to de- neighborhoods [26]. Moreover, the economic recession, ini- scribe some data. tiated in 2008, has impacted mortality and its inequalities First, age-standarized mortality rates per 100,000 popula- [27, 28]. tion (ASMR) in 38 neighborhoods were estimated by Despite a rapid increase in immigration from period, using the direct method and the total population of low-income countries, studies on immigrant mortality in Barcelona in 2001 as the reference, and ASMR were de- Spain are scarce. Immigration patterns may play an im- scribed with maps of quartiles, using time-varying ranks, in portant role in trends in socioeconomic geographical in- men and women (Fig. 1). Spearman correlation coefficients equalities in mortality, especially in places such as between unemployment and ASMR were calculated. Then, Barcelona where there is selective residential immigra- deaths and populations were obtained across neighbor- tion [6]. The objective of this study was therefore to hoods, grouped by unemployment quartiles, and ASMRs by analyze the trend in socioeconomic inequalities in mor- neighborhood unemployment groups were estimated, bian- tality in the foreign-born and Spanish-born population nually and by period. between neighborhoods in Barcelona during the period Finally, we applied mixed Poisson regressions using 2001–2012. generalized linear mixed models [31], adjusted by age Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 Page 3 of 9 Fig. 1 Trends in age-standardized mortality rates per 100,000 inhabitants (ASMR) in men and women aged 25–64 years in neighborhoods in Barcelona 2001–2012 and education, and levels of neighborhood unemploy- neighborhoods, and almost 25% of men and women ment, to estimate the fixed effects or mortality relative in the rest of the city. risk (RR), based on Laplace Approximation, and their It is worth mentioning that the majority of 95% confidence intervals, using normal approximation foreign-born population (around 75% in the 3 periods) (95% CI). The models included two random effects to belongs to the 25–44 years age group, 20% to the 45–64 consider the intracorrelation, both within neighborhoods years age-group and 5% to the > 64 age-years group. (spatial) and across years (temporal). These figures for the Spanish-born population are ap- proximately 40%, 30%, 30%. Results Between 2001 and 2012, a total of 26,148 premature In Barcelona, the population aged 25–64 increased deaths (25–64 years) occurred in Barcelona (67.1% men 8% between 2001 and 2012 (Table 1). Although the and 32.9% women), 24,270 with all socioeconomic infor- number of Spanish-born men and women decreased, mation (92.8%). Approximately 9% of premature deaths the number of foreign-born residents increased, with occurred in foreign-born residents, with slight variation this increase being higher in disadvantaged neighbor- between neighborhoods and periods. The number of hoods (with high unemployment rates). In these premature deaths decreased in Spanish-born men and neighborhoods, in the first period (2001–2004), women, but increased in the foreign-born population foreign-born residents represented 24.1% of men and (Table 1). However, ASMR (Table 2) showed that prema- 18% of women but less than 14% of residents in the ture mortality rates decreased in both the Spanish and rest of the city. In the second period (2005–2008), foreign-born populations. ASMR were lower among the foreign-born population increased, representing women than men and also were lower among the 38.1% of men and 30.4% of women residing in de- foreign-born population than the Spanish-born popula- prived neighborhoods, and 20% in the rest of the city. tion in both men (Fig. 2a) and women (Fig. 2b). In the last period (2009–2012) the foreign-born popu- The spatial pattern observed in premature mortality was lation increased slightly, representing 42.5% of men related to unemployment in the neighborhoods, in both and 36.7% of women residing in deprived men and women in all periods (Fig. 1). Mortality rates were Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 Page 4 of 9 Table 1 Period trends in deaths and population by neighborhood unemployment in men and women aged 25–64 years by country of birth in Barcelona 2001–2012 Number of deaths (%) Population (%) 2001–04 2005–08 2009–12 2001–04 2005–08 2009–12 Men Total Q1 Low unemployment 7.6–9.8% 1195 (100.0%) 1161 (100.0%) 1013 (100.0%) 415,382 (100.0%) 436,905 (100.0%) 441,156 (100.0%) Q2: 10–10.7% 1252 (100.0%) 1146 (100.0%) 992 (100.0%) 371,715 (100.0%) 395,836 (100.0%) 404,034 (100.0%) Q3: 10.7–12.2% 1995 (100.0%) 1870 (100.0%) 1672 (100.0%) 578,679 (100.0%) 615,689 (100.0%) 632,077 (100.0%) Q4 High unemployment −12.4-17.2% 1458 (100.0%) 1313 (100.0%) 1149 (100.0%) 333,631 (100.0%) 380,819 (100.0%) 373,893 (100.0%) Spanish-born Q1 Low unemployment 7.6–9.8% 1107 (92.6%) 1075 (92.6%) 929 (91.7%) 361,239 (87.0%) 344,997 (79.0%) 330,581 (74.9%) Q2: 10–10.7% 1202 (96.0%) 1076 (93.8%) 901 (90.8%) 323,979 (87.2%) 311,058 (78.6%) 295,873 (73.2%) Q3: 10.7–12.2% 1919 (96.2%) 1757 (94.0%) 1544 (92.3%) 511,561 (88.4%) 491,877 (79.9%) 468,396 (74.1%) Q4 High unemployment −12.4-17.2% 1363 (93.5%) 1205 (91.8%) 1018 (88.6%) 253,210 (75.9%) 235,656 (61.9%) 214,831 (57.5%) Foreign-born Q1 Low unemployment 7.6–9.8% 88 (7.4%) 86 (7.4%) 84 (8.3%) 54,143 (13.0%) 91,908 (21.0%) 110,575 (25.1%) Q2: 10–10.7% 50 (4.0%) 71 (6.2%) 91 (9.2%) 47,736 (12.8%) 84,778 (21.4%) 108,161 (26.8%) Q3: 10.7–12.2% 76 (3.8%) 113 (6.0%) 128 (7.7%) 67,118 (11.6%) 123,812 (20.1%) 163,681 (25.9%) Q4 High unemployment −12.4-17.2% 95 (6.5%) 108 (8.2%) 131 (11.4%) 80,421 (24.1%) 145,163 (38.1%) 159,062 (42.5%) Women Total Q1 Low unemployment 7.6–9.8% 701 (100.0%) 625 (100.0%) 664 (100.0%) 468,952 (100.0%) 488,479 (100.0%) 491,290 (100.0%) Q2: 10–10.7% 594 (100.0%) 588 (100.0%) 566 (100.0%) 406,262 (100.0%) 427,504 (100.0%) 435,767 (100.0%) Q3: 10.7–12.2% 903 (100.0%) 938 (100.0%) 888 (100.0%) 608,030 (100.0%) 641,385 (100.0%) 657,834 (100.0%) Q4 High unemployment −12.4-17.2% 577 (100.0%) 515 (100.0%) 495 (100.0%) 304,844 (100.0%) 333,849 (100.0%) 334,953 (100.0%) Spanish-born Q1 Low unemployment 7.6–9.8% 658 (93.9%) 560 (89.6%) 596 (89.8%) 404,790 (86.3%) 385,990 (79.0%) 366,927 (74.7%) Q2: 10–10.7% 560 (94.3%) 545 (92.7%) 509 (89.9%) 354,154 (87.2%) 340,339 (79.6%) 321,210 (73.7%) Q3: 10.7–12.2% 862 (95.5%) 880 (93.8%) 808 (91.0%) 541,249 (89.0%) 521,330 (81.3%) 494,220 (75.1%) Q4 High unemployment −12.4-17.2% 545 (94.5%) 472 (91.7%) 428 (86.5%) 249,838 (82.0%) 232,325 (69.6%) 212,029 (63.3%) Foreign-born Q1 Low unemployment 7.6–9.8% 43 (6.1%) 65 (10.4%) 68 (10.2%) 64,162 (13.7%) 102,489 (21.0%) 124,363 (25.3%) Q2: 10–10.7% 34 (5.7%) 43 (7.3%) 57 (10.1%) 52,108 (12.8%) 87,165 (20.4%) 114,557 (26.3%) Q3: 10.7–12.2% 41 (4.5%) 58 (6.2%) 80 (9.0%) 66,781 (11.0%) 120,055 (18.7%) 163,614 (24.9%) Q4 High unemployment −12.4-17.2% 32 (5.5%) 43 (8.3%) 67 (13.5%) 55,006 (18.0%) 101,524 (30.4%) 122,924 (36.7%) higher in neighborhoods with higher unemployment rates last period, 2009–2012 (RR = 1.33, 95%CI = 1.14–1.55. (Spearman correlations were 0.72 and 0.42 in the period Nevertheless, socioeconomic inequalities in premature mor- 2009–2012 in men and women, respectively). tality were observed only in Spanish-born men (RR = 1.43, When the data were analyzed by neighborhood un- 95%CI = 1.21–1.68 in 2001–2004, RR = 1.34, 95%CI = 1.14– employment groups (Table 2), premature mortality rates in 1.58 in 2005–2008 and RR = 1.36, 95%CI = 1.15–1.61 in men were higher in disadvantaged neighborhoods and these 2009–2012). In foreign-born men, there was no excess mor- socioeconomic inequalities persisted across all periods. The tality in disadvantaged neighborhoods., except during the mortality relative risk, between neighborhoods with higher last period, 2009–2012, but it was not significant. In and lower unemployment rates, was higher in 2001–2004 women, premature mortality was higher in disadvantaged (RR = 1.40, 95%CI = 1.21–1.62), decreased in 2005–2008 neighborhoods (RR = 1.25, 95%CI = 1.05–1.47 in 2001– (RR = 1.30, 95%CI = 1.12–1.51) and remained stable in the 2004 and RR = 1.27, 95%CI = 1.07–1.51 in 2005–2008), but Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 Page 5 of 9 Table 2 Period trends in age-standardized mortality rates per 100,000 inhabitants (ASMR) and relative inequalities in mortality by neighborhood unemployment (RR), in men and women aged 25–64 years by country of birth, Barcelona 2001–2012 ASMR RR (CI95%) 2001–04 2005–08 2009–12 2001–04 2005–08 2009–12 Men Total Q1 Low unemployment 7.6–9.8% 293.4 270.3 233.6 1 1 1 Q2: 10–10.7% 356.4 308.8 260.3 1.06 (0.91–1.24) 1.00 (0.86–1.16) 0.96 (0.83–1.13) Q3: 10.7–12.2% 359.9 322.6 282.8 1.03 (0.90–1.19) 1.00 (0.87–1.15) 1.01 (0.87–1.16) Q4 High unemployment −12.4-17.2% 490.9 426.6 375.1 1.40 (1.21–1.62) 1.30 (1.12–1.51) 1.33 (1.14–1.55) Spanish-born Q1 Low unemployment 7.6–9.8% 299.3 286.7 252.6 1 1 1 Q2: 10–10.7% 370.3 328.6 279.7 1.08 (0.92–1.28) 0.99 (0.84–1.17) 0.94 (0.79–1.12) Q3: 10.7–12.2% 371.9 341.5 308.2 1.05 (0.90–1.22) 0.99 (0.85–1.15) 0.99 (0.85–1.16) Q4 High unemployment −12.4-17.2% 537.2 500.5 450.1 1.43 (1.21–1.68) 1.34 (1.14–1.58) 1.36 (1.15–1.61) Foreign-born Q1 Low unemployment 7.6–9.8% 254.2 159.4 129.5 1 1 1 Q2: 10–10.7% 215.7 171.5 144.7 0.75 (0.52–1.08) 1.01 (0.72–1.40) 1.16 (0.85–1.59) Q3: 10.7–12.2% 235.4 176.4 143.3 0.80 (0.57–1.11) 1.11 (0.81–1.50) 1.08 (0.80–1.46) Q4 High unemployment −12.4-17.2% 293.7 160.3 150.1 0.90 (0.65–1.25) 1.01 (0.73–1.38) 1.19 (0.87–1.61) Women Total Q1 Low unemployment 7.6–9.8% 145.5 122.3 128.3 1 1 1 Q2: 10–10.7% 146.4 136.9 128.2 0.95 (0.80–1.12) 1.05 (0.89–1.25) 0.94 (0.80–1.12) Q3: 10.7–12.2% 148.3 145.7 134.0 0.94 (0.81–1.10) 1.10 (0.94–1.29) 0.97 (0.83–1.14) Q4 High unemployment −12.4-17.2% 196.7 167.4 159.7 1.25 (1.05–1.47) 1.27 (1.07–1.51) 1.18 (0.99–1.40) Spanish-born Q1 Low unemployment 7.6–9.8% 153.0 128.2 138.3 1 1 1 Q2: 10–10.7% 150.7 144.5 138.1 0.94 (0.78–1.13) 1.08 (0.89–1.31) 0.99 (0.78–1.14) Q3: 10.7–12.2% 152.7 155.8 145.3 0.95 (0.80–1.12) 1.14 (0.96–1.36) 0.99 (0.83–1.18) Q4 High unemployment −12.4-17.2% 212.0 193.7 185.9 1.28 (1.06–1.54) 1.38 (1.14–1.67) 1.23 (1.02–1.49) Foreign-born Q1 Low unemployment 7.6–9.8% 92.5 96.2 82.6 1 1 1 Q2: 10–10.7% 107.7 85.0 81.0 1.16 (0.73–1.82) 0.87 (0.59–1.27) 0.95 (0.67–1.36) Q3: 10.7–12.2% 100.3 76.7 76.1 1.08 (0.70–1.67) 0.83 (0.58–1.19) 0.91 (0.66–1.27) Q4 High unemployment −12.4-17.2% 98.5 70.9 91.6 1.05 (0.65–1.68) 0.75 (0.50–1.11) 1.02 (0.72–1.44) the excess mortality was reduced in the last period and was Spanish-born population. Premature mortality decreased not significant (RR = 1.18, 95%CI = 0.99–1.40 in 2009– during the period but socioeconomic inequalities in 2012). However, as in men, socioeconomic inequalities in mortality in the Spanish-born population were stable premature mortality were observed only in Spanish-born and no inequalities were found between neighborhoods women and also in the last period, whereas no excess mor- in foreign-born men and women. Although socioeco- tality was observed in foreign-born women in disadvantaged nomic inequalities emerged between neighborhoods in neighborhoods. foreign born men and women in the last period, when the economic crisis began, these were non-significant Discussion among men. Evidence of the ‘healthy migrant’ effect in This study has shown that premature mortality rates mortality and socioeconomic mortality inequalities was were higher in disadvantaged neighborhoods and in the found in Barcelona, which seems to alter the distribution Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 Page 6 of 9 a Men Men Total Men Spanish-born Men Foreign-born 600 500 400 300 200 100 0 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 Q1 Low unemployment Q2 Q3 Q4 High unemployment b Women Women Total Women Spanish-born Women Foreign-born 300 250 200 150 100 50 0 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 2001-02 2003-04 2005-06 2007-08 2009-10 2011-12 Q1 Low unemployment Q2 Q3 Q4 High unemployment Figure 2 a Biannual trends in age-standardized mortality rates per 100,000 inhabitants (ASMR) by country of birth in men aged 25–64 years by neighborhood unemployment, Barcelona 2001–2012. b Biannual trends in age-standardized mortality rates per 100,000 inhabitants (ASMR) by country of birth in women aged 25–64 years by neighborhood unemployment, Barcelona 2001–2012 of mortality through time and space, related to the low are concentrated in socioeconomically deprived areas levels of premature mortality. Also it is important the se- [26]. The rapid and strong population growth has re- lective residence of immigrants in socioeconomically dis- sulted in significant changes in segregation and the advantaged neighborhoods. Therefore, these migration emergence of ethnic enclaves in Barcelona in the last effects would thus lead to false conclusions about trends decade, reflecting the diversity of nationalities and access in socioeoconomic inequalities in mortality unless the to the housing market [7]. migrant population is taken into account. Healthy migrant effect on mortality Socioeconomic spatial concentration of immigrants We showed that the foreign-born population had lower In Barcelona, the adult population aged 25–64 years old levels of premature mortality than the Spanish-born increased in last decade mainly due to the arrival of the population. This migrant mortality advantage has been immigrant population, largely in socioeconomically de- widely studied. In Europe, many studies have revealed prived neighborhoods. This finding agrees with previous low levels of premature mortality among the immigrant descriptions of the residential concentration patterns of population [9, 15–17]. The hypothesis of the “healthy immigrants in Barcelona, where the migrant population migrant” effect agrees with the main characteristics of Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 Page 7 of 9 the foreign-born population in Barcelona and other these results seem to be related to changes observed in metropolitan areas of Spain [6]. However, over time, this deprived neighborhoods affecting population health: protective effect may weaken, diminishing the relative first, the arrival of immigrants and rejuvenation of the advantage of migrants over locally/born people [20]. population [6] and second, the continuous processes of This could explain why, in our study, excess mortality urban regeneration programs [39], although these appeared in foreign-born men in socioeconomically de- changes may also produce some displacement of vulner- prived neighborhoods in the last period studied. able populations [40]. Healthy migrant effect on socio-spatial inequalities in Economic crisis mortality When the current global economic crisis started in There is growing evidence of a consistent geographical 2008, the positive trend observed in Barcelona in prema- pattern of socioeconomic inequalities in mortality in ture mortality and mortality inequalities seemed to start European cities [3]. In addition, in Spain the excess mor- to change in some vulnerable groups [41, 42]. In Spain, tality found in socioeconomically disadvantaged areas due to the economic crisis, the number of employed for- has remained stable in several cities [32]. However, the eigners decreased by half a million and unemployed rose present study found that in Barcelona this stabilized un- to 1 million at the end of 2010. As employment fell, im- equal pattern was observed only in premature mortality migration flows also rapidly declined and the number of in the Spanish-born population, with no inequalities foreigners stopped increasing [5]. This vulnerable situ- observed in the foreign-born population. ation could be related to excess premature mortality In addition, the greater effect of immigrants was among foreign-born men in socioeconomically disadvan- observed in socioeconomically deprived neighborhoods, taged neighborhoods, and among foreign-born men and related to the higher increase in the number of migrants, women with a low educational level, supporting the hy- in line with studies conducted in Montreal [33], and pothesis of the negative effect of the economic crisis on London [24] and a previous study in Barcelona [26], mortality inequalities [27, 28]. where socio-spatial inequalities in mortality decreased in part related to the increase in the migrant population. Strengths and limitations Our results are in line with studies based on large pro- This study provides new evidence on trends in neighbor- spective cohorts in the Netherlands [34] and Canada hood socioeconomic inequalities in premature mortality [19], which found a modifying effect of immigration on in the native and foreign-born population in a southern area inequalities in mortality: area income inequalities European urban setting. To our knowledge, few studies were associated with mortality among the have analyzed the effect of international immigration on non-immigrant population only; in contrast, associations trends in spatial socioeconomic inequalities in mortality. among immigrants were either absent or protective. Some strengths of this study are the large population Although the healthy migrant effect was observed base, the complex data design, controlling both temporal similarly in men and women, in line with other studies and spatial variability and using both individual and con- [13, 15–17, 34], the magnitude of neighborhood socio- textual measures of socioeconomic position, and also economic inequalities in premature mortality found in providing specific evidence by gender. the Spanish population was higher in men than in Nonetheless, this study has some limitations. First, women. One possible explanation lies in the specific caution should be exercised in detecting geographic in- causes of death in premature mortality in men and equalities when using a repeated cross-sectional design women [34]. In men, the main causes of premature mor- unless selective movement of people is taken into ac- tality were closely related to socioeconomic position and count. In Barcelona, the intensity of residential mobility socioeconomic context such as cardiovascular disease, has increased over the last decade, especially as a conse- lung cancer and external causes [35]; however these quence of the foreign population, which represented causes decreased in Barcelona [36, 37]. In women, the about half the number of residential changes registered main causes of premature were cardiovascular disease in the city in 2008 [6]. Additionally, some studies using and breast cancer [35], which in Barcelona held constant different information sources and based on mortality over time and showed no differences between socioeco- re-estimation, have revealed a two-fold underestimation nomic groups [38]. of mortality among foreigners due to a biased death nu- As a result of this evidence, the relation between merator and population denominator [43], but this socioeconomic factors and mortality could be masked underestimation does not appear to be sufficient to ex- unless immigration is accounted for, and trends in ex- plain the whole mortality advantage [8, 10]. The present cess mortality observed in socioeconomically deprived study used data recorded in the municipal population neighborhoods might be underestimated. In Barcelona, register and vital statistics, including all individuals who Rodríguez-Sanz et al. International Journal for Equity in Health (2019) 18:37 Page 8 of 9 habitually live in the municipality, being a reliable source Authors’ contributions of information on the immigrant population [44]. Maica Rodríguez-Sanz designed the study with the help of other authors, analyzed the data and wrote the first draft. All authors reviewed and wrote Other limitations are the absence of second-generation successive drafts, discussed the results and approved the final version of the immigrants, and we cannot account for the ‘salmon ef- article. All authors agree to be accountable for all aspects of the work in fect’ bias. However, we expect this bias has been attenu- ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. ated because the young and older populations have been excluded, limiting our study population to persons aged Ethics approval and consent to participate 25–64 years. This article uses secondary data and for this reason does not have ethics approval. Because of the small number of the foreign-born population, we did not analyze the influence of the Consent for publication country of origin. In Barcelona, the most frequent coun- This article uses secondary data. tries of origin were poor but with different cultural and historical backgrounds between the ethnic communities Competing interests The authors declare that they have no competing interests. (Latin American, Arabic and Asian). Various studies have shown some differences in mortality patterns by origin, reflecting some cultural and socioeconomic de- Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in terminants of migrants in the host country and country published maps and institutional affiliations. of origin [12]. 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