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Health & Wellness

Home Is Where the Hurt Is

Slone Epidemiology Center uncovers link between zip codes and health

BU epidemiologist Yvette Cozier has studied the effect of poorer neighborhoods on the health of black women. Photo by Sandy Hatfield, Slone Epidemiology Center

There is a health gap among American women, and it has stymied public health officials and health-care providers for years. Black women are afflicted with several major diseases, such as colon cancer and heart disease, at higher rates than white women. And when black women have these diseases, they more often die from them. For instance, they are 35 percent more likely to die of breast cancer, according to the National Cancer Institute.

These disparities persist even among women of the same education and income levels. Now, research from Boston University’s Slone Epidemiology Center suggests that part of the blame could lie in the neighborhoods where black women tend to live.

In a study appearing in this month’s American Journal of Public Health, Yvette Cozier, a School of Public Health assistant professor of epidemiology, found that living in a poorer neighborhood increases a black woman’s risk for hypertension (high blood pressure), which is itself a risk factor for heart disease and kidney disease. This result was found even among women whose personal characteristics, such as higher incomes, frequent exercise, and relatively low body mass index, would tend to mitigate their risk.

Nationwide, hypertension affects about 24 percent of all adults. But its incidence among black women is between two and three times that among white women. To investigate the reasons for this, Cozier and a team of researchers from the Slone Center, the SPH department of epidemiology, and Smith College used data from the ongoing Black Women’s Health Study (BWHS), administered by the Slone Center and Howard University since 1995.

The BWHS compiles data from about 59,000 black women nationwide, who provide information on their overall health, including diet, exercise, tobacco use, and any health problems they’ve experienced, by means of a mailed questionnaire every other year. Researchers use this data to track associations between risk factors and the diseases to which black women are disproportionately susceptible.

Cozier decided to study so-called “neighborhood effects,” based on research indicating that black women tend to live in poorer neighborhoods than do white women of the same education and income. She and her fellow researchers identified cases of hypertension among BWHS participants with U.S. census information connected to their addresses, including median household income, percentage of residents with white-collar jobs and college degrees, and proportion of families headed by single female parents.

Of all these variables, median housing value was most closely correlated with hypertension. Overall, women living in neighborhoods with the lowest housing value had a 30 percent greater risk of high blood pressure than did women in neighborhoods with high property values. The researchers also found a significant association between housing value and hypertension risk even after adjusting for median household income, education, and common health risk factors. For instance, among the thinnest women, a group generally considered at low risk for hypertension, incidence of the condition among residents of poorer neighborhoods was 76 percent greater than it was among those in wealthier communities.

“These results really point us in the direction that community does matter in determining individual health,” says Cozier. “Physicians and health-care providers need to be aware of that when dealing with patients or putting together a public health program.”

It’s not enough to advise black women to exercise and eat a healthier diet to decrease their disease risk, she says, when their neighborhoods lack resources such as safe places to exercise and convenient stores to buy healthy foods.

The hypertension study is one of the first looking at neighborhood effects to come out of the BWHS, according to Lynn Rosenberg, an SPH professor of epidemiology and the principal investigator for BWHS. But Cozier’s research, Rosenberg says, is part of a growing number of studies showing that “it’s not just the personal characteristics of people and their health behaviors that affect their health.”

In addition to studying neighborhood effects, researchers from BWHS have been looking into the role of genetics in disease susceptibility. One recent study questionnaire included questions about family disease history, and the researchers have obtained between 25,000 and 26,000 cheek cell samples from study participants for DNA analysis. In a related effort, this fall Boston University and Howard University began another collaboration — scanning samples of African-American DNA for genetic associations with common health ailments, including hypertension.

“It’s being discovered more and more that genes and environmental factors don’t act in a vacuum and that disease is often the result of some kind of interaction between them,” Rosenberg explains.

Cozier’s next step could be to see if similar associations exist between median housing value and other diseases prevalent among black women. She hopes also to learn more about the correlation her study uncovered — the particular aspects of poorer neighborhoods that are most detrimental to good health. 

“We still need research to know what exactly is the mechanism that goes from community to individual health,” she says.

Or, as Rosenberg puts it, “If this country is really serious about reducing health disparities, it’s got to get serious about reducing some of the inequities in the way people live.”

Chris Berdik can be reached at cberdik@bu.edu.