Fall 2017

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Segregation Linked to Elevated Blood Pressure

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Longitudinal study finds blood pressure drop among African Americans who move to less segregated areas.

Segregation impacts blood pressure and harms the health of African Americans, says Kiarri Kershaw, an assistant professor of preventive medicine. “I believe it’s related to the stress of living in these neighborhoods,” says the social epidemiologist, whose work focuses on understanding the contributions of the social environment to cardiovascular health and health disparities.

Kershaw led a Northwestern Medicine study that found the systolic blood pressure readings of African Americans dropped between one and five points when they moved to less segregated neighborhoods. It is the first study to look at the longitudinal blood pressure effects of living in less segregated areas and to compare the effect within the same individuals.

“In a less violent area with better resources, you are more secure about your family’s safety and your children’s future.” — Kiarri Kershaw

The study examined longitudinal associations of racial residential segregation with blood pressure in more than 2,000 African American participants of the Coronary Artery Risk Development in Young Adults study, a national study of adults who have been followed for 30 years (Kershaw used data from the 25-year follow-up). For African American participants who started out in highly segregated neighborhoods (80 percent of the sample), systolic blood pressure dropped 1 mm Hg for those who moved to less segregated neighborhoods. Systolic blood pressure is a greater predictor of heart attacks and strokes in African Americans than diastolic blood pressure.

The participants’ reductions in blood pressure were even more dramatic for a subset of individuals from highly segregated neighborhoods who moved to and remained in low or medium segregated residential areas. Their systolic blood pressure fell from 3 to 5 mm Hg.

“This is a powerful effect,” Kershaw says. “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.”

Less stress, achieved by decreasing exposure to violence and improving opportunities for socioeconomic mobility, is likely a key factor in blood pressure reductions, Kershaw says.

“In a less violent area with better resources, you are more secure about your family’s safety and your children’s future in better schools,” Kershaw says. “You see opportunities for the economic mobility of your kids. And there is better access to good grocery stores, health care and an economically vital business district.”

Racial disparities in hypertension prevalence and related health outcomes represent one of the largest and most persistent sources of health inequities in the United States.

“Several strategies need to be employed at the policy level to reduce the persistent racial health disparities we see in the U.S.,” Kershaw says. “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.”

Such resources include better quality schools and access to public transportation, parks, clinics and supermarkets.

“Findings from our study suggest social policies that reduce segregation, such as the opening of housing markets, may have meaningful health benefits such as the reduction of blood pressure,” Kershaw says.

Kershaw’s work in this field isn’t done yet. She is collecting data in different neighborhoods throughout Chicago to understand how people’s food environment affects their eating decisions. She is using primary data collection and simulation modeling to understand whether and how modifying the food environment influences eating behaviors and obesity.

It’s another way that segregation can influence blood pressure, and Kershaw is excited to see what she finds.