For African-Americans, the isolation of living in a racially segregated neighborhood may lead to an important health issue: higher blood pressure.
A study published Monday in JAMA Internal Medicine suggested blacks living in such areas experienced higher blood pressure than those living in more diverse communities. Moving to integrated areas was associated with a decrease in blood pressure, and those who permanently stayed in localities with low segregation saw their pressure fall on average nearly 6 points.
Kiarri Kershaw, assistant professor of preventive medicine at Northwestern University in Chicago and lead author of the study, said the findings reinforce the close relationship between social policy and community health outcomes.
“It lends credence to the notion that we should bring public health practitioners and health policy officials to the table to make these decisions,” she said. Researchers used data from a long-term study that has followed 2,280 African-Americans over the course of 25 years, checking in every three to seven years to track blood pressure.
Heart disease is the leading cause of death in the United States, and African-Americans are disproportionately affected by the condition. According to the American Heart Association, 46 percent of non-Hispanic black men and nearly 48 percent of non-Hispanic black women live with a form of heart disease, while about 36 percent of non-Hispanic white men and 32 percent of non-Hispanic white women do.
Georges Benjamin, executive director of the American Public Health Association, said the burden to address such disparities falls on society at large.
“It doesn’t just hurt African-Americans or people of color. This hurts everybody,” he said. “Because everyone pays not just in terms of humanity, but in terms of dollars.”
Doctors generally record two numbers for blood pressure: the diastolic pressure — the blood’s force inside the veins when the heart is at rest — and the systolic pressure, which gauges the blood’s force when the heart beats. Blood pressure is measured in millimeters of mercury, or mmHg (using mercury’s chemical element symbol), with systolic pressure reported first, such as 115 mmHg over 75 mmHg.
Researchers found residential segregation was associated with changes in systolic blood pressure, which is tied to adverse cardiovascular events, such as a heart attack. The findings did not show any changes in diastolic blood pressure.
The scientists also collected data on a variety of other social indicators including level of education, poverty and marriage status. They ranked the level of segregation in participants’ neighborhoods as “low,” “medium” and “high” based on the number of African-Americans in the larger area.
When compared to African-Americans living in highly segregated locations, participants living in medium-segregation neighborhoods recorded blood pressure that was on average 1.33 mmHg lower. Those residing in low-segregation areas were an average 1.19 mmHg lower.
Blood pressure for black residents who permanently moved into medium segregation locations decreased on average 3.94 mmHg. African-Americans who stayed in low-segregation locales saw an average decrease of 5.71 mmHg.
Although single-digit changes do not appear impressive, a separate study published in 2015 found a 1 mmHg decline in blood pressure led to 20 fewer heart failures and 10 fewer cases of coronary heart disease and stroke per 100,000 black individuals.
“At the population level, a 1 mmHg reduction can result in substantial reduction in poor cardiovascular events,” Kershaw said.
The research is part of the Coronary Artery Risk Development in Young Adults (CARDIA) study, partially funded by the federal government, which has tracked participants since 1985. The four CARDIA sites are Chicago, Birmingham, Ala., Minneapolis and Oakland, Calif.
For several decades, researchers have been looking into the effects of residential segregation on health disparities. A 2001 article by David R. Williams and Chiquita Collins identified segregation as a “fundamental cause of racial differences in health” because of its role in dictating access to other determinants of health like education and employment.
Mark Huffman, a practicing cardiologist and assistant professor of preventive medicine and medicine-cardiology at Northwestern University, said this study’s findings reinforce the importance of his patients’ environments. Medicine alone cannot address the disparities created by segregation, he said, and practitioners must be cognizant of how well their patients can adhere to the recommendations given to them in the doctor’s office.
“I need to get to know my patients — about where they live and what it’s like — to be able to understand how they can implement my recommendations … that are easy to say and hard to implement,” said Huffman. “And certainly harder to implement if doctors don’t understand where their patients live, work and play.”