Racial, economic segregation linked to cancer mortality
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High levels of racial and economic segregation appeared associated with higher cancer mortality rates across more than 3,000 U.S. counties, according to results of an ecological study.
The findings, published in JAMA Oncology, showed a 20% increased risk for cancer mortality among residents of highly segregated counties compared with residents of integrated counties.
Background and methods
Residential segregation has a long history in the U.S. and although overt segregation is now illegal, racial minority and low-income groups are still separated from privileged white populations in many areas, Lu Zhang, PhD, assistant professor in the department of public health sciences at Clemson University, told Healio.
“Residential segregation has been shown to be a structural risk factor for several adverse health outcomes,” Zhang said. “However, the association between residential segregation and cancer mortality has not been comprehensively investigated.”
Zhang and colleagues examined this association across 3,110 U.S. counties for all cancer types and for the 13 most deadly cancer types.
Researchers reviewed county-level sociodemographic data from the 2015 to 2019 American Community Survey linked with county-level mortality data from the same period. They used multilevel linear mixed modeling to calculate adjusted mortality rate ratios and measured residential racial and economic segregation by the Index of Concentration at the Extremes (ICE) and categorized counties into five quintiles, with quintile 1 being the most deprived and quintile 5 being most privileged.
Age-adjusted cancer mortality served as the main outcome.
Findings
Results showed age-adjusted mortality rates for all cancers for the five ICE categories of 179.8 per 100,000 population for the most deprived counties, followed by 177.3, 167.6, 159.6 and 146.1 for the most privileged counties (P < .001 for trend).
Researchers observed adjusted mortality rate ratios — compared with the most privileged counties (quintile 5) — of 1.22 (95% CI, 1.2-1.24) for the most deprived counties (quintile 1), 1.17 (95% CI, 1.15-1.19) for the second quintile, 1.1 (95% CI, 1.09-1.12) for the third quintile and 1.06 (95% CI, 1.04-1.08) for the fourth quintile.
Moreover, researchers found associations of segregation with increased mortality for 12 of the 13 most common cancer types, including adjusted RRs that ranged from 1.06 (95% CI, 1.02-1.09) for brain and other nervous system cancers to 1.49 (95% CI, 1.43-1.54) for lung and bronchus cancers.
“Although we hypothesized that residential segregation was associated with cancer mortality, the strength of the associations still surprised us,” Zhang said. “Residents of highly segregated counties had a 50% increased risk for lung cancer mortality vs. those living in integrated counties.”
Implications
The findings indicate that residential segregation is a social determinant of health, according to Zhang.
“To improve cancer outcomes and reduce disparities, efforts are needed to address this structural risk factor and intervene on the factors that mediate residential segregation and cancer outcomes,” she said. “The pathways between segregation and cancer outcomes are still not clear. Therefore, our team will continue to investigate the mechanisms of the associations between segregation and cancer outcomes to inform interventions for reducing the impact of segregation on health.”
The neighborhood factors that underlie the association between racial residential and economic segregation and poor cancer outcomes did not happen overnight, according to an accompanying editorial by Victoria L. Seewaldt, MD, associate director of population sciences research and chair and professor in the department of population sciences at City of Hope, and Robert A. Winn, MD, director and Lipman chair in oncology at VCU Massey Cancer Center.
“These poor cancer outcomes are the result of longstanding racist and discriminatory policies implemented at the national, state and individual level, such as redlining and chronic disinvestment,” they wrote. “To remedy these inequities, formerly redlined neighborhoods need to be made safe and walkable. Highways that were built to divide and destroy [Black] neighborhoods need to be rerouted — and neighborhoods reconnected and revitalized. To reduce the effect of heat, parks and green spaces need to be placed in formerly redlined neighborhoods.”
Change is needed to end these disparities in cancer mortality, they continued.
“The will to change needs to come from all levels and from all people — but especially from neighborhoods,” they wrote. “In the words of Thurgood Marshall, ‘Where you see wrong or inequality or injustice, speak out, because this is your country. This is your democracy. Make it. Protect it. Pass it on.’”
References:
- Seewaldt VL, et al. JAMA Oncol. 2022;doi:10.1001/jamaoncol.2022.5272.
- Zhang L, et al. JAMA Oncol. 2022;doi:10.1001/jamaoncol.2022.5382.
For more information:
Lu Zhang, PhD, can be reached at lz3@clemson.edu.
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