(How) Does Where You Live Get Under Your Skin?

Originally posted 11/2/2011

Last week Kirstin blogged on an innovative housing project in the South Bronx that incorporated fitness promoting design principles. She cited the Robert Wood Johnson Foundation’s Commission to Build a Healthier America’s Issue Brief on Housing and Health which identified three interrelated aspects of residential housing that influence health: (1) affordability, (2) the physical conditions within homes, and (3) neighborhood environments surrounding homes.

Last week there was significant media coverage (including the October 29 Economist!) of an article by Jens Ludwig and colleagues that was featured in the Oct 20 New England Journal of Medicine. The study reported that moving from a high poverty neighborhood to a lower poverty one showed substantial improvement in obesity rates and blood sugar levels. Why was this report deemed of such interest and importance, even by the mainstream press?

There is no disputing that these are provocative findings. While those in the field of public and population health have understood for some time that the social determinants of health are probably as important as health care and individual behaviors, this concept is not yet fully appreciated. When asked what influences health, my sense is that the public as well as many policymakers are much more likely to list health care (procedures/drugs/immunizations) and the physical environment (air/water/restaurant sanitation) than socially-mediated influences such as income, education, housing, and neighborhood “environment.”  

The science of how social factors get “under the skin” to indirectly produce disease is complex and the field is still in its relative infancy, which makes it that much more difficult – and that much more important — to translate this type of research into policy.

In this study, the investigators took advantage of a policy experiment sponsored by the Department of Housing and Urban Development. From 1994 to 1998, 1800 of almost 5000 women with children living in public housing in high poverty urban areas were randomly assigned to receive vouchers allowing them to move to a low poverty census tract. Follow-up on these women was conducted from 2008-2010 on a variety of factors. Compared to the control group, the women had lower BMI over 35 (13%), BMI over 40 (19%), and HgA1c (a blood glucose diabetes indicator, 22%). The study was not designed to figure out what caused these effects, although the authors speculate that stress associated with residential segregation in poverty areas may be responsible. The Economist coverage suggests a possible linkage with food deserts in high poverty areas, although the study did not explore this. Other possible contributing factors include toxic exposures, parks and sidewalks,  crime/violence and perceptions of safety, social connections, and the quality of local institutions like schools and employment opportunities.

It’s entirely possibly – likely even – that the heightened media attention on the study reflects the current national milieu. With the recent “occupy” protests across the country, economic inequality is likely to play a prominent role in the 2012 elections. But politics aside, I believe the study deserves attention for its methodological rigor. The study employed a randomized design, which is rare due to cost and often ethical considerations. In the physical and biological sciences test tube experimental conditions often allow the manipulation of variables so that causal relationships can be made with some certainty. In social sciences we are often limited to weaker statistical relationships, which often fall short when trying to convince policy makers to invest differently.

The Ludwig study is not without some methodological limitations, and we still don’t know how moving to lower poverty neighborhoods gets under the skin to reduce weight and glucose levels. But the results are consistent with theory and other studies, and give us reason to choose healthy policies in all domains. It should also encourage foundations and government to fund similar experiments. Working simultaneously on both policy and research fronts will help ensure steady progress toward our goal of determining how to best invest our scarce resources for the greatest population health gain.

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