Author: Richa Shivakoti
Last update: 01/10/2019
Type 2 diabetes, also known as non-insulin dependent or adult-onset diabetes, is a result of the body’s inability to use the insulin it produces. Type 2 diabetes comprises the majority of people with diabetes around the world and is a growing global epidemic. It is estimated that the number of people with diabetes has risen from 108 million in 1980 to 422 million in 2014, which is a prevalence of 8.5% among the global adult population (World Health Organization, 2016). It is expected to reach 629 million by the year 2045 (International Diabetes Federation, 2017). Diabetes can significantly impact the quality of life, particularly through its complications, as it is an important contributor to blindness, kidney failure, lower limb amputation, and other long-term consequences. The total burden of deaths from high blood glucose levels in 2012 was estimated to be 3.7 million, with 1.5 million directly caused by diabetes. Globally, annual healthcare costs of affected individuals were estimated at US$727 billion in 2017 (International Diabetes Federation, 2017). Low and middle-income countries carry almost 80% of the diabetes burden.
The number of people living with any form of diabetes mellitus has quadrupled in the past three decades, and diabetes is now the ninth major cause of death globally (Zheng, Ley, & Hu, 2018). The major driving factors of the global T2DM epidemic include genetic predisposition, growing numbers of overweight and obese individuals, unhealthy diets, and sedentary lifestyles. The interplay of genetic and environmental factors may support higher prevalence rates of Type 2 diabetes among migrant populations, and the risk of developing the disease may be higher among particular migrant groups living in specific destination country contexts. This review therefore explores prevalence rates of Type 2 diabetes among migrant populations and suggests areas where additional research would be needed to understand the factors that differentially shape the risks of migrant versus non-migrant populations in developing Type 2 diabetes.
Overview of current situation
Migrant populations, especially in destination countries in the global north, have been found to be at increased risk of developing diabetes in various studies. Several studies have found that the prevalence rates of diabetes for migrants is much higher than native-born populations and that some migrant and ethnic groups have a predisposition to diabetes and develop diabetes at younger ages. For example, Asians have a strong ethnic and genetic predisposition to diabetes. As a result, they develop diabetes at a younger age and at a lower body mass index and waist circumference when compared with non-Asian populations (Ramchandran, Snehalatha, Shetty, & Nanditha, 2012). In Europe, higher incidences of diabetes, increased complications arising from diabetes, and different mortality rates have been observed among migrants in comparison to the native population, which relate to genetic profiles, lifestyle, and utilization of healthcare systems in different ways (Testa, Bonfigli, Genovese, & Ceriello, 2016).
Risk factors for type 2 diabetes among migrant populations
The linkages between migration and diabetes are complex, as multiple factors may play a role in a person developing diabetes. Such factors are shaped by conditions and processes in countries of origin, countries of destination, and within migration journeys and processes. A mix of social, environmental, cultural and genetic determinants such as socioeconomic status, family history, diet, obesity, physical activity, ethnicity, sex and age all shape an individual’s risk of developing diabetes. With migration, some of these factors may shift. For example, the ‘healthy migrant effect’—in which migrants are initially healthier than the native population—diminishes over time as migrants’ lifestyles and behaviours converge to those of the host country, which may in turn affect a migrant’s risk of developing conditions such as diabetes.
Demographic factors, lifestyle and environmental factors, and access to healthcare are specific factors identified in the literature that support increased prevalence of diabetes among migrant populations. Issues such as urbanization, change in nutrition and lifestyle behaviours, obesity, physical inactivity, and stress are important factors that may particularly shape the risks migrant groups face in developing diabetes. Culture is also important, as it shapes individuals’ values and perspectives on health and can affect health though health-related behaviours and the use of healthcare.
Some studies have compared diabetes prevalence rates among migrant and native populations and found inflated prevalence among migrants. For example, in the Netherlands a study found the prevalence of diabetes to be 2-3 times higher for Turkish and Moroccan migrants compared to the indigenous Dutch population. The study also found that diabetes occurred at younger ages among Turks by a decade and among Moroccans by two decades (Ujcic-Voortman, Schram, Jacobs-van der Bruggen, Verhoeff, & Baan, 2009). Similar findings were uncovered in a study of African migrants in the United Kingdom, with the prevalence of type 2 diabetes among African migrants found to be between 3-5 times higher than that among European-descent populations and age of onset found to be younger (Oldroyd, Banerjee, Heald, & Cruickshank, 2005; Testa et al., 2016). The 2004 Health Survey for England found that after adjusting for age, doctor-diagnosed diabetes was almost 4 times as prevalent in Bangladeshi men and almost 3 times as prevalent in Pakistani and Indian men as compared to men in the general population. Prevalence was also higher among migrant women compared to women in the general population, with diabetes 5 times more prevalent among Pakistani women, at least 3 times more prevalent among Bangladeshi and Black Caribbean women, and 2.5 times more prevalent among Indian women (The Information Centre, 2006). Another study using pooled data from the 1997-2005 US National Health Interview Survey on immigrant adults found that both men and women from the Indian subcontinent were more likely than European migrants to have diabetes without corresponding increased risk of being overweight. It also found that men and women from Mexico, Central America, or the Caribbean were more likely to be overweight and to have diabetes than were European migrants (Oza-Frank & Venkat Narayan, 2010). A study from Australia found that across all socio-economic strata, all migrant groups had higher prevalence of T2DM than the Australian-born population (Abouzeid, Philpot, Janus, Coates, & Dunbar, 2013).
Other studies have explored morbidity and mortality rates of migrants compared to the general populations in countries of destination, with several finding poorer health outcomes among migrants. One study found that diabetes-related mortality was higher among migrant populations compared to local-born populations in Europe, with the highest diabetes mortality observed for migrants from South Asia, North Africa, the Caribbean, and Turkey (particularly among women) (Vandenheede et al., 2012). Another study from the UK observed higher morbidity and mortality from type 2 diabetes and related complications among African migrants compared to persons of European-descent (Oldroyd, Banerjee, Heald, & Cruickshank, 2005; Testa et al., 2016). Other studies have compared diabetes risks and prevalence rates between migrants and their non-migrant counterparts who remained in the home country. For example, a comparison of Ghanaians living in Europe to the general population in Ghana found higher risk of obesity and type 2 diabetes among sub-Saharan African populations living in Europe and high prevalence rates in urban environments in Ghana (Addo et al., 2017; Agyemang et al., 2016). Another study comparing the risk factors associated with type 2 diabetes and prediabetes in Asian Indians in India and in the US found that the age-adjusted diabetes prevalence was higher in India than the US, while the age-adjusted prediabetes prevalence was lower in India than the US (Gujral et al., 2015).
Research Gaps and Policy Recommendations
Even though several studies have found a higher prevalence of diabetes among migrants when compared with various native populations, they are usually unable to determine whether differences in prevalence rates were caused by differences in genetic disposition or differences in environmental or cultural factors. The difficulty in disentangling these agents often reflects methodological and measurement challenges. For example, data that contains appropriately nuanced indicators of migration status, health status, and environmental and cultural factors are scarce, and limited data distinguishes between first and second-generation migrants. It is recommended that governments invest in collecting such data so it can support improved evidence-based policies for diabetes linkages for migrant populations.
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