By Dr. Geoffrey Modest
There have been many studies finding that poverty or living in poorer neighborhoods is associated with increased morbidity or mortality. However, it is hard to dissociate the array of potential risk factors associated with poverty to validate a true association (for example, do those with more morbidities overall tend to move to poorer neighborhoods since their income tends to be lower, etc. (“social drift”) – so that the association is really with the burden of increased morbidities?). In this light, a quasi-experimental situation existed in Sweden finding that those refugees assigned to poorer neighborhoods had more diabetes (See White JS. Lancet Diabetes Endocrinol 2016; 4: 517).
Details:
- 61,386 refugees aged 25-50, who arrived in Sweden from 1987-91, were assigned to one of 4833 different neighborhoods in a quasi-random fashion (90% of all refugees were randomly assigned. Those reuniting with family members or those with financial resources to support themselves were not randomly assigned). The goal of Sweden’s policy was to distribute the refugee workforce more evenly throughout the country. All refugees received Swedish language and training courses and social welfare support for about 18 months. There was no restriction on the refugees’ subsequent mobility within Sweden.
- 85% were 25-34 yo, 74% married/cohabitating, 30% with 2 children, 45% from the Middle East/northern Africa or Iran/19% Eastern Europe/14% Latin America
- The neighborhoods were classified as high deprivation, moderate deprivation, or low deprivation based on the different levels of poverty and unemployment, schooling, and social welfare participation.
- 45% of refugees were assigned to a moderate-deprivation and 47% to high-deprivation neighborhoods, though only 8% to a low-deprivation one.
- They excluded any with diagnoses of diabetes within the first 5 years after arrival in Sweden, as a means to filter out those with incipient diabetes.
- Primary outcome was the diagnosis of type 2 diabetes between 2002-2011
Results:
- Cumulative diabetes incidence was 5.8% in low-deprivation, 7.2% in moderate-deprivation, and 7.9% in high-deprivation neighborhoods, with background diabetes prevalence in Sweden being 4-6%
- In adjusted models, being assigned to high- vs low-deprivation neighborhoods was associated with a 22% increased risk of diabetes [OR 1.22 (1.07-1.38), p=0.001], and moderate- vs low-deprivation neighborhoods having a 15% increased incidence.
- Diabetes risk accumulated over time: 5 years of additional exposure to high-deprivation vs low-deprivation neighborhoods was associated with a 9% increased diabetes risk
Commentary
- So, this study does account for some of the expected different circumstances which could account for some of the preselection bias of differences in morbidity/mortality in people living in communities of differing deprivation levels (e.g., social drift).
- The resulting diabetes incidence differences are therefore likely related to neighborhood-specific differences, such as that those living in poorer neighborhoods tend to eat cheaper and less healthy foods that predominate there, have fewer psychosocial supports, and have less access to safe exercise venues.
- However, this was not a true randomized trial, especially because those refugees with higher incomes may have opted out of this process and there was a significantly lower % assigned to the low-deprivation areas. So, that does limit the generalizability of the conclusions somewhat (though the numbers of people involved and the differences they found in diabetes incidence were quite impressive)
- There is an important social context here: though there were significant differences in the low vs high deprivation neighborhoods in Sweden, overall these differences are much more profound in the US, where both the basic differences between neighborhoods is more striking (higher income inequality) and the available social resources in the poorer communities are considerably less (Sweden is known for its strong public safety net).
For more blogs on the relationship between socio-economic status (SES) and morbidity/mortality, see:
https://stg-blogs.bmj.com/bmjebmspotlight/2016/07/13/primary-care-corner-with-geoffrey-modest-md-ses-and-mortality/ reviewed a different Swedish study finding that those with diabetes who had lower socio-economic status had higher rates of all-cause, cardiovascular, diabetes-related mortality.
And an array of blogs in the grouping https://stg-blogs.bmj.com/bmjebmspotlight/category/psychosocial/ which look at BMI, height and the attendant SES; life expectancy and income; income disparities and life expectancy; etc.