Black individuals with prostate cancer experience the largest racial disparity in both incidence and mortality of any cancer in the US.^1,2 In addition to genetic factors, disparities in prostate cancer are driven in part by the intersection of structural and social determinants of equity and health.^3,4 Historical events dating back to the trans-Atlantic slave trade have shaped current structural, social, and economic disparities. Slavery in the US set the precedent for the normalization of interpersonal, structural, and systemic racism, which has legitimized an array of laws and practices that routinely advantage White populations while producing cumulative and chronic adverse outcomes for people of color.⁵ The downstream effects of this history impact health care access, delivery, and health behaviors, which in turn contribute to the poorer outcomes we observe in a range of health conditions.

We hypothesize that historical slavery, which is the major inciting event for modern-day structural racism, may be strongly associated with both present-day social determinants of health and prostate cancer incidence. To this end, we devised an ecological study to evaluate the correlation between measures of county-level proportion of enslaved people in the United States in 1860 and present-day prostate cancer incidence among Black and White individuals.

To address the complex structural-social-environmental-biologic interactions that drive cancer incidence and detection, we adapted prior conceptual models to create a new framework that would guide the selection of county-level social determinants of health to add to our statistical models.

Prostate cancer data at the county level were obtained from State Cancer Profiles for 16 Southeastern states in the US.⁶ Total population estimates were derived from the National Center for Health Statistics Bridged-Race Resident Population Estimates for 2015-2019 online database.⁷ Social determinants of health variables were obtained from the American Community Survey (US Census). County- level slavery data were obtained from the 1860 Decennial Census. We applied areal interpolation to map county boundaries from 1860 to modern-day geographic borders.^8,9 Spatial maps were constructed to overlay prostate cancer incidences, the percentage of enslaved persons by county, and selected social determinants. We calculated adjusted incidence rate ratios for the association between county-level historical levels of slavery and prostate cancer incidence.^10,11

Counties in Mississippi and Louisiana tended to have the largest percentages of enslaved individuals in 1860, as well as modern-day prostate cancer incidences. Spatial maps and correlations reveal some of the highest concentrations of enslaved individuals in counties around the Mississippi-Louisiana border (nearly all counties with >80% enslaved population in 1860), central Alabama, Georgia, and into South Carolina (nearly all counties with >60% enslaved population in 1860). Counties in these areas also demonstrate the highest rates of present-day prostate cancer incidence–to–poverty ratios. Strong associations were found between historical slavery and poverty, insurance status, unemployment, and low birth weight. Our multivariable results indicated that after having controlled for all other social variables, every 10% increment in historically enslaved populations in a county was associated with higher county-level incidence of prostate cancer in White men (1.009; 1.003-1.014; P < .01) and Black men (1.014; 1.005-1.024; P < .01).

Although we initially hypothesized that historical slavery would only be associated with prostate cancer incidence among Black Americans, we found a significant association with higher prostate cancer incidence for both White and Black Americans in Southeastern US areas with a higher history of enslaved populations. Historical slavery was also correlated with numerous social determinants of health. The impact of the trans-Atlantic slave trade is woven into the fabric of our health care systems, laws and policies, economic systems, and other fundamental components of life in America. Our analysis demonstrates that this relationship does exist and independently correlates with present-day prostate cancer incidences for both Black and White men. Our study is limited by a lack of genetic data, suppression of incidence data in low-population counties, and unmeasured confounding. The strength of our analysis lies in the novel data linkages and data approaches taken to rigorously evaluate the relationship between a profound historical event and current-day cancer outcomes.

Adverse and inequitable health outcomes have been born out of the tragic and horrific history of slavery that aided the development of our health care systems and research institutions. There is no doubt that this history, which includes experimentation on enslaved people, Black people, and other marginalized populations over a more than 200-year time period, influences and impacts present-day health behaviors and decisions among Black patients. The norms, economies, and policies born out of historical slavery (ie, Jim Crow laws, redlining, mass incarceration) have created structural barriers and a sociopolitical culture that disadvantages not just Black individuals, but individuals of all races who inhabit the communities that were most affected by slavery across the US. This is evidenced by the racial biases in our care and medical decision aids.^12-17 Our analysis demonstrates that the complexities of these interactions are deeper than the correlation between a historical event such as the trans-Atlantic slave trade and present-day structural and social determinants of health and equity. Our findings suggest that our policy solutions for addressing health inequities in diseases such as prostate cancer must acknowledge, account for, and directly address the legacy of historical events that have disadvantaged marginalized communities, such as the tran-Atlantic slave trade.