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Leaving segregated neighborhoods linked to lower blood pressure among blacks, study finds

REUTERS/Lucy Nicholson
Research has suggested that even small changes in blood pressure at the population level can save thousands of lives.

For black adults, moving out of racially segregated neighborhoods is associated with a decline in blood pressure — a drop significant enough to result in a reduction in heart attacks and strokes, according to a study recently published in JAMA Internal Medicine.

The study examined data collected over several decades from more than 2,000 black adults who, at the start of the study, lived in highly segregated neighborhoods in four major metropolitan areas — including Minneapolis. When those adults moved to a less segregated neighborhood, their systolic blood pressure fell 1 to 5 millileters of mercury (mm Hg), on average, the study found.

Furthermore, the longer they lived in a low- or medium-segregated neighborhood, the more dramatic the drop.

Those improvements may seem modest, but other research has suggested that even small changes in blood pressure at the population level can save thousands of lives. High blood pressure — or hypertension — is a major risk factor for heart disease and stroke.

“This study provides stronger, more direct evidence that segregation impacts blood pressure and harms the health of African-Americans,” said Kiarri Kershaw, the study’s lead author and an assistant professor of preventive medicine at Northwestern University, in a released statement. “I believe it’s related to the stress of living in these neighborhoods.”

More than two decades of data

As background information in the study points out, “residential segregation has been identified as a fundamental cause of black-white health disparities because of its effect on access to a wide range of health-promoting resources and opportunities, including quality education, health food options, and social capital.”

One of those health disparities appears to involve higher blood pressure. Indeed, some studies have found that — among black communities — the greater the segregation, the greater the prevalence of hypertension. Until now, however, no study had looked at whether blood pressure improved when people moved away from highly segregated neighborhoods.

For the current study, Kershaw and her colleagues used 25 years of data collected from 2,280 black participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study, which has been following a group of more than 5,000 black and white adults since 1985 to see what factors influence the development of heart disease over a lifetime. All of the participants were aged 18 to 30 when they were enrolled in the study.

CARDIA recruited its participants from four urban areas: Minneapolis; Chicago; Birmingham, Ala.; and Oakland, Calif.  For their study, Kershaw and her colleagues looked at the specific neighborhoods where the 2,280 black participants lived during each of the six times their blood pressure was tested over a 25-year period. They then categorized the racial segregation level of each neighborhood as high, medium or low, based on the percentage of black residents in the neighborhood compared to the percentage in the larger metropolitan area.

‘A powerful effect’

At the beginning of the study, 1,861 of the study’s participants (81.6 percent) were living in a high-segregation neighborhood, while 278 (12.2 percent) were living in a medium-segregation neighborhood and 141 (6.2 percent) in a low-segregation one. Almost all the participants (94 percent) moved at least once over the course of the study, and more than half (51.7 percent) moved three or more times. 

An analysis of the data revealed that when the participants moved out of a high-segregation neighborhood, their systolic blood pressure tended to decrease — by an average of 1 mm Hg.

Northwestern

People who moved out of highly segregated neighborhoods permanently (for the remainder of the study’s 25-year follow-up period) experienced the biggest improvements. Those individuals saw their blood pressure fall by an average of 3 to 5 mm Hg.

The findings persisted even after researchers adjusted for other factors known to influence blood pressure, including marital status, body mass index, smoking history, physical activity levels and income.

“This is a powerful effect,” said Kershaw. “In terms of impact, just 1 mm Hg of reduction of the systolic blood pressure at the population level could result in meaningful reductions in heart attacks, strokes and heart failure.”

Limitations and implications

The study is observational, which means it cannot prove a direct causal link between living in a high-segregation neighborhood and higher blood pressure. It can show only a correlation between the two. Also, although the study’s retention rates were high, some participants were lost to follow-up (did not return for all the health checkups) — a factor that may have biased the results.

Still, as Kershaw and her colleagues point out, the findings add to “the small but growing body of evidence that policies that reduce segregation may have meaningful health benefits.” 

"Several strategies need to be employed at the policy level to reduce the persistent racial health disparities we see in the U.S.," said Kershaw. "This includes policies that improve access to resources for those living in segregated neighborhoods and policies that provide residents living in segregated neighborhoods with the opportunity to move to neighborhoods with better access to resources."

Those resources include, she added, better quality schools and greater access to public transportation, parks, clinics and full-fledged grocery stores.

FMI: You can access the study through the JAMA Internal Medicine website.

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