Kiarri Kershaw, an assistant professor of preventive medicine at Northwestern University, and her colleagues followed 2,280 African-Americans participating in the Coronary Artery Risk Development in Young Adults study.
The subjects were living in highly segregated neighborhoods in Chicago, Minneapolis, Birmingham, Ala., and Oakland, Calif., when the study began in 1985. They were between the ages of 18 and 30 when the study started.
The researchers followed the study subjects for 25 years, when they reached the ages of 43 to 55. Those who moved away from highly segregated neighborhoods to less-segregated neighborhoods and stayed there during that period had significantly lower blood pressure.
Their systolic blood pressure, the first of the two numbers used to measure blood pressure, was one to five points lower, the researchers reported.
While the differences in blood pressure may seem small, that difference among a large number of people could translate into thousands fewer heart attacks and strokes over time. Systolic blood pressure is thought to be the more important number when it comes to developing cardiovascular disease.
"I think it's pretty powerful in the sense that the reasons for their moves were not necessarily for their health, but it has these other added benefits," Kershaw says.
The study did not examine how moving to less-segregated neighborhoods could affect blood pressure. But Kershaw thinks it's probably because of a combination of factors, including experiencing less stress from being exposed to less violence.
"There's a decent-size body of evidence relating stress to blood pressure and that's one pathway that we hypothesize that segregation influences health — through exposure to violence, things like that — that could increase your stress level and then potentially influence blood pressure," Kershaw says.
Less-segregated neighborhoods may also provide more economic opportunities for people and their children and access to better schools, which could also reduce stress, she says.
In addition, those neighborhoods may also make it easier to live healthier lifestyles by having more access to parks, sidewalks, gyms, grocery stores with more fresh produce and pharmacies to get medication.
The researchers found the difference in blood pressure persisted after accounting for other factors that could have played a role, such as changes in income and education.
Kershaw acknowledges, however, that moving to less segregated neighborhoods could increase stress in at least one way — by potentially exposing African-Americans to more racism.
"It's certainly possible that those who move to less segregated neighborhoods experience more exposure to racism, which could be one reason why some African-Americans choose to stay in more segregated neighborhoods," she wrote in an email. She noted that African-Americans living in more segregated neighborhoods tend to have better mental health.
But Kershaw says her study found there was an overall beneficial ffect on blood pressure of leaving a segregated neighborhood.
"The take-home message is that policies that can allow people who are living in segregated neighborhoods to move and live in more integrated neighborhoods have some spillover effects that influences health like blood pressures," Kershaw says.
Others agree. "This study is really important," says Ashish Jha, who studies health policy at the Harvard T.H. Chan School of Public Health and was not involved in the study.