Our models suggested that racial residential segregation was a risk factor for Black CRC mortality in urban Delta Region counties, a finding aligned with other CRC disparities research [24, 37]. However, we discovered an inverse relationship in rural Delta counties, namely that racial segregation was associated with lower CRC mortality. While this finding may seem surprising, the relationship between residential segregation and Black cancer outcomes remains unclear. Some studies have found detrimental outcomes (as we did for urban locales) [22–23], while others have shown protective effects (as we did for rural locales) [18, 26, 38], and others have reported non-association [19, 21, 39–40]. It is clear that the interaction of rurality and race, especially in segregated communities, deserves additional exploration in health research. A few hypotheses might provide insight into our novel findings.
First, after the insurance mandate of the Affordable Care Act (ACA) in 2014, multiple positive health outcomes were observed, including increased probability of physician visits and a reduction of overall uninsurance, with reduction in uninsurance seen more prominently in Blacks than in Whites [41]. Furthermore, increases in the percentage of people covered were found to be much greater in rural, compared to urban, settings [42]. Conceivably, rural Black residents of the Delta Region may have benefitted particularly strongly from the ACA, thereby resulting in decreased CRC mortality. Future analyses should compare CRC mortality trends by race in urban and rural Delta counties in years prior to and after the introduction of the ACA to explore whether it might explain why Black residents in segregated rural regions of the Delta experience lower rates of CRC mortality.
A second potential explanation for our findings is that rural segregated communities may have unique features that do not exist in their segregated urban analogues. Ethnic enclaves—geographical areas marked by large concentrations of people of similar races or ethnicities that often feature organizations led by members of these communities—have been shown to impart health benefits via different pathways, such as shared cultural norms [43], stronger social networks [39], increased social capital [18], and less exposure to racism-related stress [40]. However, other highly-segregated areas may be cut off from resources, access, and knowledge [8–11], thus perpetuating unequal balances of power or resources and leaving communities of color with smaller social networks and less support [18]. It is possible that these disparities are more pronounced in urban areas and that social bonds may be stronger in segregated rural communities, thus leading to improved health outcomes.
It is nonetheless important to remember that racial residential segregation is a system of oppression comprised of multiple factors that lend to long-term health outcomes. Due to segregation, Black communities have historically-entrenched and socially- and politically-enforced barriers to economic, educational, and health resources, implications from which continue to be felt today. Although the findings of this paper identified an association between reduced CRC mortality and rural Black segregation, it is important to acknowledge that multiple factors likely drive this relationship, thus underscoring the necessity for continued research dedicated to understanding the long-term effects of segregation on health outcomes.
Finally, it should be noted that our county-level data do not fully capture individual-level factors—such as comorbidities, screening data, median-age of death, or other risk factors—that might partly explain our findings. Data from the 2012–2015 Behavioral Risk Factor Surveillance System (BRFSS) show that rural Blacks self-report lower health-related quality of life, higher cost-related barriers to seeking treatment, lower CRC screening rates, and more comorbidities than rural Whites [44]. Furthermore, precancerous polyps, many of which have little or no symptoms, can take upwards of a decade to progress to CRC [45]. Perhaps, then, rural Blacks in the Delta Region are dying prematurely from complications of other causes (i.e., multiple chronic conditions) before dying from the slower developing consequences of CRC. Poor, rural Black residents have nearly three times greater risk for premature mortality than their more affluent Black and White urban counterparts [46]. Moreover, death rates from the five leading causes of death are highest in rural areas of the United States [47]. Given that the Delta Region as a whole has one of the lowest life expectancies in the country [48], our findings might not fully capture the entire picture related to trends in Black CRC mortality in the Delta Region.
Limitations
While this study imparts critical evidence in the still-inconclusive literature on the effects of racial residential segregation on health outcomes by examining how rurality moderates the relationship between segregation and colorectal cancer mortality, our findings should be interpreted with a few limitations in mind. First, we only examined one geographically isolated area of the United States, the Mississippi Delta Region. Although this region was selected purposively due to its overwhelming colorectal cancer mortality burden [2], researchers should investigate other rural, isolated areas to determine whether they differ from the Delta. Second, many counties in our analysis had missing data for CRC mortality and were thus replaced with values generated via random forest imputation. Although our imputed and non-imputed datasets were similar, there is the possibility that the imputed CRC mortality rates in this study did not truly reflect the CRC mortality rate in a particular county with missing data. Third, our study is limited by the snapshot of health represented from 2011–2015, and general implications about the effects of a socially- and legislatively-enforced historical phenomenon like segregation on health outcomes are thus limited. Fourth, given that the county was the unit of analysis in this study, we were unable to control for individual-level covariates (e.g., stage at diagnosis, median age, comorbidity scores, and individual insurance coverage) that may have partly explained our findings. Finally, our study is correlational in nature and, as such, no causal effects can be inferred based on our findings.