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A neighbourhood’s affluence is linked to its residents' risk of obesity and diabetes, a new study has found.
People living in a high-poverty area were more likely to be obese and more likely to have diabetes than those in a low-poverty census tract. The researchers characterise the association as modest but potentially important.
"The effects we see in the study are comparable to what you see from targeted lifestyle interventions or with providing people with medications to prevent the onset of diabetes," chief author Jens Ludwig of the University of Chicago told Reuters Health in a telephone interview.
He said it shows that the environment has important impacts on health.
Cause and effect not proved
The study, released online in the New England Journal of Medicine, did not directly prove cause and effect. In addition, it only measured height and weight, and recorded diabetes status at the end of the study, not at the beginning.
The conclusion comes from about 4,500 mothers living in public housing where at least 40% of the residents in the neighbourhood had incomes below the federal poverty level.
From 1994 to 1998, under the US government's Moving to Opportunity programme, 1,788 were given housing vouchers that were only good in neighbourhoods where the poverty level was less than 10%. Another 1,312 were given vouchers that were good anywhere. Both groups also got counselling on moving. The remaining 1,398 received no special vouchers and no counselling.
More than a decade later, the government did a follow-up study on the women.
Neighbourhood makes no difference
Among everyone regarded as obese, with a body-mass index of 30 or higher, the neighbourhood made no difference.
But among seriously obese women with a BMI of 35 or higher, the voucher for moving into a low-poverty neighbourhood seemed to have made a difference; about 31% of those who got the voucher had BMI's of 35 or higher, compared to about 36% who didn't get a voucher.
And 14% of the people who got voucher that let them move into a better neighbourhood were morbidly obese (with a BMI of 40 or higher) compared to 18% of those who did not get a voucher.
Furthermore, 16% of women who received a voucher to move into a low-poverty neighbourhood were diabetic, versus 20% of those who did not get a low-poverty voucher.
The results are complicated by the fact that only about half of the vouchers for moving into low poverty areas were actually used.
In addition, most people in the study ended up living in better neighbourhoods anyway. At baseline, the average poverty rate in neighbourhoods where the people lived was about 53%; the mean rate had dropped to 33% or below by the 10-year mark.
Improving environments
Ludwig expressed confidence in the results even though measurements of height, weight and diabetes were not done at the start of the study. He said the Department of Housing and Urban Development (HUD) measured 57 other variables and found that the three groups were comparable at the beginning of the study, so it's logical that obesity and diabetic levels were comparable as well.
And the fact that half the people given the special voucher to move into a low-poverty area didn't use it was not a problem because we've pooled everyone together and found a difference even when including those who didn't move, he said.
"This was an experiment that was not done by HUD to change obesity and diabetes levels. 75% signed up for reasons of safety; they wanted to get away from the crime," said Ludwig. "HUD was thinking, 'We hope this will improve their labour market outcome and get better schools for the kids.' It turns out the effect on diabetes is the same as the best medical interventions we know of. That seems pretty remarkable."
Moving to neighbourhoods with less poverty could provide easier access to health care and supermarkets with healthy food relieve everyday stress that can affect eating habits, and make it easier to find a safe place to exercise, he said. "It could be something as simple as decent sidewalks."
"Given that diabetes and obesity are associated with a large number of health complications and higher cost for medical care, the findings from this study suggest that improving the environments of low-income urban neighbourhoods might improve the duration and quality of life for the residents and lower health care expenditures," co-author Dr Robert Whitaker of Temple University said in a written statement.
(Reuters Health, October 2011)
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