EditorialThe impact of migration on cardiovascular diseases☆
Introduction
Cardiovascular disease (CVD) is now the leading contributor to disability-adjusted life years lost worldwide [1]. Within CVD, ischaemic heart disease and stroke rank first and second [1], with hypertensive heart disease and heart failure, rheumatic heart disease (RHD), cardiomyopathy and atrial fibrillation also contributing substantially [2]. There is clear international commitment to address this issue. The WHO 25 × 25 Global Action Plan [3], and the Sustainable Development Goals [4] set ambitious targets to reduce premature mortality from CVD. Yet while there has been considerable progress in many countries, this has not been matched in others, especially low and middle-income ones, with death rates in, for example, South Asia, now over three times as high as in high income countries [2], [5].
These differences in levels and trends in CVD matter in a world experiencing high levels of migration. Those migrating, within or across national boundaries, may have patterns of disease that differ from the existing population, due to features of both where they have come from and where they have arrived. Of course, while there have been many mass migrations in the past, such as the expansion of European populations into the Americas and Australasia, who to varying degrees displaced existing populations [6], or the movement of entire nationalities in the aftermath of the Second World War [7], the scale of migration to Europe in particular since the beginning of the 21st century, has been on a scale not seen for many decades, much of it a consequence of conflict and environmental factors.
Knowledge of how these developments are influencing the pattern of disease in populations is essential for those involved in planning services in areas experiencing high levels of migration so as to enable them to plan and implement appropriate health services and targeted prevention interventions [8]. Here it is important to note that the pattern of settlement is extremely uneven. Thus, even within Europe, some countries have experienced relatively little recent migration, such as the United Kingdom, reflecting its government's policy of creating a “hostile environment” [9], a situation that also applies in many countries of central Europe, while others have been much more welcoming, exemplified by the German term Willkommenskultur, or “welcoming culture”, that has seen the absorption of over one million migrants in 2015. Moreover, within those countries that have received large numbers of migrants, the new arrivals are often concentrated predominantly in urban environments.
The information needed may not, however, be easy to obtain. Much of our knowledge of the causes of CVD comes from research on existing populations in high-income countries [3], [8], [10], [11], [12], [13], defined by their residence of a country or community [11] or their occupation or employer [14]. The evidence they have provided shows how the causes of CVD operate at many levels [2], [15], from proximal risk factors, both modifiable, both behavioural (diet, smoking, alcohol, physical activity) and metabolic (blood pressure, cholesterol, diabetes), and non-modifiable, such as age and gender. Other studies have assessed the impact of upstream and community determinants of CVD related to the physical and social environments, including what are termed the social determinants of health [16], including poverty, inequality, and the political and economic factors that create them, [8] as well as the roles of health systems, urbanization and pollution [2], [17]. There is much less research on those populations from which people are now migrating, including both exposures and outcomes [18].
In this paper we review some of the key issues relating to the impact of international migration flows on cardiovascular disease dynamics, proposing a conceptual framework for assessing the health effects of different steps in the migration process, which we then use of explore some of the ways in which these steps can influence CVD risk. Recognizing the constraints of space, we do not look in detail at the associated challenge of internal displacement, although this also raises important issues for health policy makers. We also recognize that the available literature is dominated by studies of migrants moving to high-income countries, even though most international migrants are in other low and middle-income countries. We then make suggestions for how the burden of CVD might be addressed in migrant populations.
We argue that there are three key factors influencing CVD burden in migrant populations: i) conditions in the country of origin, including ethnicity, access to life sustaining treatment, and the reasons why people migrate; ii) the migration process itself, and iii) legal status in the host country. Although previous research has to a very large extent focused on each separately, [19] we view them as part of a dynamic, complex continuum.
Given the complexity of migration, of necessity this review must be limited. Thus, it focuses primarily on ischaemic heart disease, its risk factors, and consequences. We note, but do not address further, the high burden of rheumatic heart disease in many parts of the world [20] and Chagas Disease among migrants from South America [21]. It also excludes issues related to the large numbers of migrants moving between rich countries, such as Northern Europeans retiring to the Mediterranean [22], although they too pose challenges for those providing health services.
Section snippets
CVD in migrant populations: a conceptual framework
Research on the health of migrants typically combines successive phases of the migratory process with a life-course perspective [23], [24]. Zimmerman et al. [23] identified five phases of the migration process: i) pre-departure, ii) travel, iii) destination, iv) interception, and v) return. In this review, we apply this framework to CVD. The framework is depicted graphically in Fig. 1, distinguishing the role of CVD risk factors in host countries, the migration selection process, and the risks
Reasons to migrate, and what it means for patterns of CVD?
When seeking to understand the complex pattern of CVD in migrant populations it is important to reflect upon “who migrates”. The scope of migration is broad and includes different forms of human mobility: temporary or more permanent, over long or shorter distances, [23] forced or voluntary [19]. There are various taxonomies of migration status, depending on the question being asked. Some are based on legal factors, such as residence status (citizen, permanent/temporary resident, undocumented
Pre-migration risk factors impacting on CVD epidemiology in migrants
Pre-migration risk factors for CVD include ethnicity and proximal and distal environmental determinants. The concept of ethnicity encompasses both genetic and cultural differences, which may be intertwined with geographic differences [5]. Migrant studies have revealed important differences in CVD rates among places and populations, [35], [36], [37], [38] some of which reflect variations among ethnic groups [38], [39], [40]. However, the precise combination of explanations is often more
Post-migration risk factors impacting on CVD epidemiology in migrants
The risk of CVD in migrant populations reflects, at least in part, changing living conditions and lifestyles in the host countries. The time dimension refers to both to the life course of individuals (years since immigration) and the accumulated influence of migration across generations, including the degree of assimilation.
Three main factors impact on migrants' CVD risk in host countries: i) changing lifestyle and “acculturation”, ii) access to care and iii) socioeconomic status.
Acculturation
The impact of migration on the epidemiology of CVD
The level and distribution of CVD in a population is influenced by many factors, including the composition of the population. Contrary to the situation portrayed in the popular press in some countries, the scale of migration to most high-income countries has been relatively modest, and to many it has been virtually insignificant. However, in a few places, such as some cities, there has been a demonstrable change in the composition of the population. Those newly arrived and, in some cases, those
The way forward
We know that globalization, urbanization and migration add complexity to the epidemiology of CVD, [65] so it is of crucial importance to understand how they influence the burden and nature of CVD and to adapt health systems and health service delivery to changing needs. Migration requires new ideas to be applied to health policy and practice, informed by evidence derived from contextually relevant research to support them. Although migrant health has traditionally been framed mainly as being
Acknowledgements
We are grateful to Bayard Roberts and Fouad Fouad for comments on an earlier draft.
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The authors report no relationships that could be construed as a conflict of interest.