Although first-generation immigrants with type 2 diabetes from non-Western nations appear to have a survival advantage compared with native Swedes with diabetes, this protective effect reduces over time and vanishes in second-generation immigrants, new research suggests.
"Our data indicate that in type 2 diabetes patients, exposure to the Swedish environment seems to have a larger impact on mortality risk than region of origin," explained Louise Bennet, MD, PhD. She presented the findings from the 10-year Swedish population-based study at the virtual meeting of the European Association for the Study of Diabetes (EASD).
Initially, immigrants from non-Western countries (defined as those in the Middle East, Asia, Africa, Latin America, and Caribbean) who develop type 2 diabetes appear to have a survival advantage over native Swedes with diabetes. But that advantage seems to diminish over time spent in Sweden and was not seen among children, said Bennett, of Lund University.
"For second-generation immigrants and people staying a long time in Sweden, we think acculturation to the Western culture has a strong impact together with socioeconomic factors. A big proportion settled in socioeconomically vulnerable areas, which, together with gene–environment interactions, can increase their risk of morbidity and mortality," she observed.
In Sweden today, one in five people was born abroad, with particularly large communities from the Middle East, Africa, and Asia. Those immigrants to Europe are at high risk for type 2 diabetes. Access to healthcare is universal in Sweden though, so that is not a factor, Bennett pointed out.
Commenting on the study, Lucy Chambers, head of research communications at Diabetes UK, said: "These new findings show a potential link between adapting to a Western lifestyle and an increased risk of dying in people with type 2 diabetes who immigrated from countries with non-Western cultures."
"While the study didn't specifically look at the health behaviors of the participants, we do know from previous research that factors related to a Western lifestyle, such as eating habits and low activity levels, contribute to the risk of developing complications in type 2 diabetes," she added in a statement from Diabetes UK.
"This research is a reminder that everyone living with type 2 diabetes, regardless of their heritage and where they live, should have the support they need to eat a healthy, balanced diet and be physically active."
Immigrants From Non-Western Nations Initially at Lower Risk
Bennet and colleagues examined data from the National Board of Health and Welfare as well as Statistics Sweden based on glucose-lowering drug prescriptions, causes of death, immigration/emigration, and demographics.
The study population included 138,085 people who developed new-onset type 2 diabetes between 2006 and 2012 in Sweden, including 74% native Swedes, 21% first-generation immigrants, and 5% second-generation immigrants (one or both parents).
Average age at diagnosis of type 2 diabetes was higher for native Swedes (60.6 years) and for immigrants from Europe or North America (57.8 years) and their children (56.3 years). The average age at diagnosis for non-Western first- and second-generation immigrants was 51.2 and 43.6 years, respectively.
After adjustment for age at diabetes diagnosis, sex, type 2 diabetes treatment, education, income, occupation, and region of residence, all-cause mortality through 2016 was 54% lower for first-generation immigrants from non-Western countries versus native Swedes, a significant difference (hazard ratio, 0.46).
Analyses showed that death rates fell with older age at migration and shorter stay in Sweden.
Mortality rates did not differ between immigrants from other Western countries and native Swedes.
Hazard ratios for cardiovascular mortality compared with native Swedes were 0.37 for non-Western and 0.95 for Western immigrants. The same pattern was even seen for cancer mortality, with hazard ratios of 0.70 and 1.06, respectively.
Risk Increased With Years Living in Sweden
The longer people spent living in Sweden, however, the higher their mortality risk.
For first-generation immigrants residing there for 24 years or less, the hazard ratio for all-cause death was 0.55, so still much lower than for native Swedes, but this waned to a risk of 0.92 if they had lived in Sweden for longer than 24 years, which was not significantly different from the risk of death among native Swedes.
And for children of immigrants, the all-cause mortality risk for those with two foreign-born parents was actually significantly higher than for native Swedes (1.28), although not significantly different for those with only one immigrant parent (1.08). There were no significant differences in cardiovascular disease or cancer mortality.
"We need to focus awareness on second-generation immigrants with diabetes, optimize nonpharmacological and drug prevention to improve metabolic control, and reduce the future risk of diabetic complications," Bennet said.
"Future research should examine a combination of risk factors including lifestyle, migration history, epigenetics, and social and contextual factors."
The study will be published in Diabetologia.
Bennett has reported no relevant financial relationships. Chambers is an employee of Diabetes UK.
EASD 2020. Presented September 23, 2020. Abstract 84.
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