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Cancer Mortality in the Mississippi Delta Region:
Descriptive Epidemiology and Needed Future Research and Interventions
Abstract

The Delta Region is a federally designated, socioeconomically disadvantaged region of the United States covering 252 counties in eight states along the Mississippi River. The objective of this study is to describe the Region’s cancer mortality burden. National Center for Health Statistics data were used to calculate age-adjusted mortality rates and rate ratios for the Delta Region for all cancers, lung, colorectal, breast (female), cervical, and prostate cancers. Rates were also calculated for comparison groups, and were stratified by gender, race, rurality, and socioeconomic status. The all-cancer mortality rate in the Delta Region was higher than all comparison groups across all stratifications. Higher rates were seen for cervical and colorectal cancer across comparison groups and stratifications. Delta Blacks had higher rates than Whites, and rural Delta residents had higher rates than their urban peers for most cancers. Further research and interventions should be conducted to elucidate and reduce these disparities.

Key words

Rural health, minority health, neoplasms, epidemiology

Cancer disparities in the United States are often most unfavorable for minority and low-income populations.1 While the connection between poverty and cancer morbidity and mortality is often studied, cancer links involving poor, rural populations are not as frequently studied. Whatever the racial, socioeconomic, or geographic context, cancer disparities often occur because of lack of access to care, individual health risk factors (e.g., smoking, obesity), and less frequent cancer screening.2-4 These disparities often manifest themselves in poorer outcomes, including shorter survival times and higher mortality rates.5 [End Page 315]

The Delta Regional Authority (Delta Region) is a federally designated region of over 10 million residents in 252 counties across eight states (Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee) along the Mississippi River and the Alabama Black Belt (Figure 1).6 It is a federal-state partnership established in 2000 to foster regional economic development. This region is poor, largely rural, and has a high proportion of Black residents. More than one in five Delta Region residents (20.6%) live in poverty (compared with 14.9% nationwide), and approximately 32.4% of residents are of Black race.6 Furthermore, the Delta Region is also largely rural. In the Delta Region, the population density is 64.9 persons per square mile, compared with 89.5 persons per square mile in the United States as a whole.6

Large portions of the Delta Region have experienced sustained high mortality rates compared with the country as a whole.7 Specifically, one study found that Delta Region residents were 16% more likely to die from cancer than Americans in general.8 However, there is limited research describing how these mortality rates vary by cancer site and race, or in comparison with other regions including regions with similar socioeconomic disparities like Appalachia.8-9 The objective of this paper is to describe the burden of cancer mortality in this socioeconomically disadvantaged region.

Methods

Figure 1. Map of the United States showing the Delta Regional Authority (DRA) Counties.
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Figure 1.

Map of the United States showing the Delta Regional Authority (DRA) Counties.

We analyzed National Center for Health Statistics (NCHS) mortality data accessed through the National Cancer Institute’s Surveillance Epidemiology and End Results [End Page 316] (SEER) program.10 SEER*Stat 8.2.1 software was used to calculate age-adjusted cancer mortality rates per 100,000 population and 95% confidence intervals (CI) using the 2000 U.S. standard population for the most recently available interval of data (2008-2012).11 Cancers were categorized by site using the ninth and tenth revisions of the International Classification of Disease (ICD-9 and ICD-10) and include all (total) cancers, breast (female), cervical, prostate, lung, and colorectal cancers. These cancer types were chosen because they include the leading causes of cancer death, and they have available screening modalities and/or are heavily influenced by modifiable behaviors (e.g., smoking) that may be amenable to public health interventions.

Age-adjusted mortality rates were calculated by geographic region and were stratified by gender, race, and rural-urban status. In addition to the Delta Region, age-adjusted mortality rates were calculated for four other regions for comparison purposes: 1) the United States (U.S.); 2) all non-Delta Region counties in the U.S.; 3) all non-Delta Region counties within the eight Delta Region member states; and 4) Appalachia. These geographical distinctions allow for national, regional, and disparate regional comparisons. The nationwide and non-Delta regions provide broad, national comparisons while the comparison to the non-Delta affiliated counties in Delta Region states provides a direct regional comparison. The Appalachian contrast allows the Delta Region to be compared with another federally designated region with similar socioeconomic disparities. Appalachia has been a federally designated region since 1965, spans 420 counties and 13 states, and is characterized by lower socioeconomic status of its residents and relatively unfavorable rates of cancer morbidity and mortality.9,12-13 Rurality was determined by the United States Department of Agriculture’s Rural Urban Continuum Codes (RUCC), which categorizes counties by their population size and proximity to a metropolitan area.14 RUCCs of 1-3 were classified as urban, and RUCCs of 4-9 were classified as rural.

We also performed intra-Delta Region comparisons to assess further the impact of socioeconomic deprivation on cancer mortality rates. We did this by categorizing Delta Region counties in accordance with the Delta Regional Authority’s definition of a distressed county, then calculating the age-adjusted cancer mortality rates for each designation.15 For a county to be considered distressed, it must meet at least one of the following criteria: 1) an unemployment rate one percentage point higher than the national rate over the last two years; and/or 2) a per capita income of 80% or less of the national per capita income. Two hundred sixteen counties in the Delta Region are considered distressed, and 36 counties are non-distressed counties. While the number of counties vary considerably by this designation, the populations within these counties during the study period are more closely comparable (6,666,320 in distressed counties and 3,179,624 in non-distressed counties).

Following the precedents of other studies that made geographic comparisons of age-adjusted cancer rates, we considered there to be a statistically significant difference in rates if the 95% confidence interval of the Delta Region did not overlap the confidence interval of the rate of a comparison region.16-17 In addition to calculation of age-adjusted mortality rates, we calculated rate ratios to compare age-adjusted mortality rates between geographic regions. A p-value less than .05 is indicative of statistical significance for all analyses. [End Page 317]

Results

The 2008-2012 all-cancer age-adjusted mortality rate in the Delta Region was significantly higher than the United States as a whole (200.4 per 100,000, 95% CI = 199.2-201.6 vs. 171.2 per 100,000, 95% CI = 171.0-171.4, respectively) and was significantly higher than all other regions of comparison, including Appalachia (186.7 per 100,000, 95% CI = 186.0-187.4) (Table 1). Gender-specific all-cancer age-adjusted mortality rates were also higher in the Delta Region, especially among males compared with the United States as whole (255.5 per 100,000, 95% CI = 253.4-257.6 vs. 207.9 per 100,000, 95% CI = 207.6-208.2 respectively). Breast and cervical cancer age-adjusted mortality rates (24.9 per 100,000, 95% CI = 24.3-25.5 and 3.4 per 100,000, 95% CI = 3.2-3.6, respectively) were higher compared with the U.S. as a whole, all non-Delta Region counties in the U.S., all non-Delta Region counties within the eight Delta Region member states, and Appalachia. The Delta Region age-adjusted prostate cancer mortality rate (26.0 per 100,000, 95% CI = 25.3-26.7) was also higher than the nation as a whole, non-Delta counties nationwide, non-Delta counties in Delta Region states, and Appalachia. With the exception of female rates, age-adjusted lung cancer mortality rates were significantly higher for both females and males compared with national rates and rates in non-Delta Region counties nationwide, non-Delta Region counties in the eight Delta Region states, and Appalachia. Specifically, age-adjusted lung cancer rates were notably higher among Delta Region males compared with Appalachian males (85.2 per 100,000, 95% CI = 84.0-86.4 vs. 76.2 per 100,000, 95% CI = 75.5-76.9, respectively). Age-adjusted colorectal cancer mortality rates in the Delta Region were higher for both females and males compared with all other regions of comparison.

Age-adjusted cancer mortality rates among both Whites and Blacks were higher in the Delta compared with other regions for multiple cancer types, and rates among Blacks in the Delta were higher than their White Delta Region counterparts (Table 2). Notably, all-cancer mortality rates were higher among both Whites and Blacks in the Delta (191.6 per 100,000, 95% CI = 190.2-193.0 and 231.3 per 100,000, 95% CI = 228.6-234.0, respectively) than the nation as whole (170.9 per 100,000, 95% CI = 170.7-171.1 and 202.0 per 100,000, 95%CI = 201.3-202.7, respectively). Similarly, higher rates were seen in age-adjusted lung cancer and colorectal cancer mortality rates among both Whites and Blacks in the Delta Region compared with their peers nationwide and in Appalachia. Additionally, age-adjusted cervical, breast, and prostate cancer mortality rates in Blacks in the Delta Region were significantly higher than in Blacks in all other regions. With the exception of lung cancer mortality, Blacks in the Delta Region had higher mortality rates than their White Delta counterparts for all cancer types. This is most starkly seen in age-adjusted cervical cancer mortality rates, which were more than twice as high in Delta Region Black women as White women (5.6 per 100,000, 95% CI = 5.1-6.1 vs. 2.6 per 100,000, 95% CI = 2.4-2.8, respectively).

For most cancer types, both rural and urban cancer rates in the Delta region were higher than other regions, and rates were also higher in the rural Delta compared with the urban Delta Region (Table 3). The all-cancer age-adjusted mortality rate was higher in the rural Delta Region (205.7 per 100,000, 95% CI = 203.9-207.5) compared with the urban Delta Region (196.4 per 100,000, 95% CI = 194.8-198.0). In both the rural [End Page 318]

Table 1. AGE-ADJUSTED CANCER MORTALITY RATES PER 100,000 IN THE DELTA REGION AND OTHER REGIONS Notes: CI = Confidence Interval
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Table 1.

AGE-ADJUSTED CANCER MORTALITY RATES PER 100,000 IN THE DELTA REGION AND OTHER REGIONS

Notes: CI = Confidence Interval

[End Page 319]

Table 2. AGE-ADJUSTED CANCER MORTALITY RATES PER 100,000 BY RACE IN THE DELTA AND OTHER REGIONS Notes: CI = Confidence Interval
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Table 2.

AGE-ADJUSTED CANCER MORTALITY RATES PER 100,000 BY RACE IN THE DELTA AND OTHER REGIONS

Notes: CI = Confidence Interval

[End Page 320]

Table 3. AGE-ADJUSTED CANCER MORTALITY RATES PER 100,000 BY RURALITY IN THE DELTA AND OTHER REGIONS CI = Confidence Interval
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Table 3.

AGE-ADJUSTED CANCER MORTALITY RATES PER 100,000 BY RURALITY IN THE DELTA AND OTHER REGIONS

CI = Confidence Interval

[End Page 321]

and urban Delta Region, all-cancer mortality rates are significantly higher than cor-responding rural and urban areas of other region in the country. Age-adjusted breast cancer mortality rates in both the rural and urban Delta Region are also higher than other comparable regions, but there was no significant difference in rates between the rural and urban Delta Region. Both cervical and prostate cancer mortality rates showed a similar relationship as breast cancer with higher rates among both the rural and urban Delta Region compared with other regions, but no difference between rural and urban Delta Region. Age-adjusted lung cancer mortality rates were higher in both the rural and urban Delta Region compared with most other regions in the country, while the rural Delta had higher mortality rates than the urban Delta Region (65.9 per 100,000, 95% CI = 64.9-66.9 vs. 57.7 per 100,000, 95% CI = 56.8-58.6, respectively). Age-adjusted colorectal cancer mortality rates showed similar differences with higher rates in both the rural and urban Delta Region, and higher rates in the rural Delta Region (20.8 per 100,000, 95% CI = 20.2-21.4 vs. 18.9 per 100,000, 95% CI = 18.4-19.4, respectively).

Intra-Delta Region comparisons based upon socioeconomic designation indicated some modest differences in age-adjusted cancer mortality rates between distressed and non-distressed counties (Table 4). Distressed counties had higher age-adjusted all cancer rates than non-distressed counties for both genders combined and for males and females separately. There were no significant differences in age-adjusted breast or cervical cancer mortality rates between distressed and non-distressed counties. Distressed counties had a higher age-adjusted prostate cancer mortality rate compared with non-distressed counties. Age-adjusted colorectal cancer mortality rates for both genders combined as well as for males and females separately were modestly higher in distressed counties compared with non-distressed counties in the Delta Region.

The Delta Region had significantly higher rate ratios (RR) compared with other geographic areas for all cancers (p < .0001 for all comparisons) (Table 5). When compared with the non-Delta United States, the starkest higher rate ratios were seen with cervical cancer (RR = 1.49, 95% CI = 1.39-1.59), lung cancer (RR = 1.31, 95% CI = 1.30-1.33), and colorectal cancer (RR = 1.29, 95% CI = 1.26-1.31). When compared with non-Delta counties within the eight Delta Region states, the highest rate ratios were seen in cervical (RR = 1.28; 95%CI = 1.18-1.38) and colorectal (RR = 1.17, 95% CI = 1.14-1.20) cancers. Cervical (RR = 1.32, 95% CI = 1.22-1.44) and prostate (RR = 1.23, 95% CI = 1.19-1.27) cancers were greatest in the Delta Region compared with Appalachia.

Discussion

We used NCHS data to evaluate cancer mortality rates in the Delta Region compared with other geographic regions. The age-adjusted all-cancer and colorectal cancer mortality rates in the Delta Region for both sexes combined and for females and males separately was notably higher than other regions, including the socioeconomically disadvantaged Appalachian region. Higher rates in the Delta Region compared with other regions were observed in cervical cancer and male lung cancer mortality rates. Furthermore, both Whites and Blacks in the Delta Region had higher all-cancer and colorectal cancer mortality rates than their peers in other regions and the nation as a [End Page 322] whole. Blacks in the Delta Region had higher age-adjusted breast, cervical, and prostate cancer mortality rates than Blacks in other areas. Additionally, Blacks in the Delta Region had higher cancer mortality rates than their White Delta Region counterparts. Analysis of rural and urban cancer mortality rates indicates that, for all cancers and lung and colorectal cancers, the rural Delta Region had higher rates than their urban Delta Region counterparts. In both the rural and urban Delta Region, age-adjusted mortality rates for breast, prostate and cervical cancers were higher than rural and urban comparison regions. Differences between cancer mortality rates in distressed and non-distressed counties within the Delta Region were either modest or not statistically significant. Rate ratios indicated significantly higher rates in the Delta Region, compared with all other regions for all cancer types, including the similarly disparate Appalachian region. Cervical cancer mortality showed the highest rate ratio when comparing the Delta Region with other regions.

Table 4. CANCER MORTALITY RATES PER 100,000 IN DISTRESSED AND NON-DISTRESSED COUNTIES IN THE DELTA REGION Notes: CI = Confidence Interval
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Table 4.

CANCER MORTALITY RATES PER 100,000 IN DISTRESSED AND NON-DISTRESSED COUNTIES IN THE DELTA REGION

Notes: CI = Confidence Interval

To our knowledge, our study is the first to describe the comprehensive cancer mortality burden in the Delta Region as a federally designated region. Our findings corroborate previous studies showing an increased risk of cancer-related death and higher rates of colorectal cancer mortality in the Lower Mississippi Delta region, which [End Page 323]

Table 5. CANCER MORTALITY RATE RATIOS IN THE DELTA REGION *p &lt; .0001 Ref = reference group
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Table 5.

CANCER MORTALITY RATE RATIOS IN THE DELTA REGION

*p < .0001

Ref = reference group

[End Page 324]

overlaps much of the Delta Regional Authority’s Delta Region designation, compared with the nation as a whole.8,18 However, there is still a dearth of studies exploring cancer disparities in the Delta Region as a federally designated region. Additionally, our study is the first to compare cancer rates in the Delta Region to a similarly disadvantaged region—Appalachia. The lack of studies may be due, in part, to the fact that the Delta Regional Authority is a relatively new designation (created by congressional legislation in 2000).6 In comparison, Appalachia was federally designated as a region that would benefit from targeted economic development since 1965 and has also benefitted from substantial studies examining health based upon region-specific data.14 Our findings underscore the importance of research to elucidate the causes of these increased cancer mortality rates in the Delta Region to help guide development of interventions to effectively target this regional disparity.

Additionally, these analyses indicate that racial disparities exist in the Delta Region, and that the cancer burden in Blacks in the Delta Region was greater than their peers nationwide and in other similarly disparate regions such as Appalachia. The higher cancer mortality burden among Blacks supports previous studies that have indicated racial cancer disparities nationwide and within the Lower Mississippi Delta region.19-20 However, the increased cancer mortality rates in Blacks in the Delta Region compared with another disparate region, Appalachia, indicates that further research should be conducted to better understand the etiology of Delta-specific racial disparities. This will, in turn, help researchers, public health professionals, and clinicians better target needed interventions.

We also found that cancer mortality varied between the rural Delta Region and other rural regions in the country. This corroborates some of our previous work evaluating intra-rural differences in cancer incidence.21-22 Previous research utilizing the SEER 18 registries found that both rural lung and colorectal cancer incidence different by SEER region.21 We also found that, in Illinois, lung cancer incidence rates differed across rural regions of the state, even after accounting for smoking and socioeconomic status.22 Such findings suggest that regions such as the Delta Region and Appalachia, while similarly rural and poor, should not be seen as homogeneous. Furthermore, as suggested by Meilleur and colleagues, these findings underscore the importance of considering rurality as a contextual factor, not solely a descriptive factor, for cancer outcomes.23

Additionally, our findings indicated that there were either no differences or only modest differences in age-adjusted cancer mortality rates between distressed and nondistressed counties in the Delta Region dependent upon the cancer type. These findings are similar to those of a study exploring cancer incidence in Appalachia in which they found that there was virtually no difference in cancer incidence rates between Appalachian counties with greater socioeconomic deprivation and more affluent counties.24 This suggests that, within these designated regions, factors beyond socioeconomics may play a role in cancer disparities. Specifically, our findings indicate that there may be a confluence of geographic, social, cultural, health care access, and environmental factors, outside of economic factors, within the Delta Region that may affect cancer mortality. However, future research could both help explicate the effect of socioeconomics on cancer mortality in the Delta Region using more refined measurements and assess other factors that affect poorer cancer outcomes in the Region. [End Page 325]

The higher mortality rates for the cancers examined suggest that the Delta may benefit both from public health and health promotion efforts targeting cancer screening access and uptake and health behavior modification (e.g., smoking cessation), and from collaborative efforts of researchers, clinicians, and community-based organizations. For example, Appalachia has experienced similar cervical cancer disparities, and interventions have effectively increased Pap smear screening adherence.25 Similar interventions, but based upon regional characteristics, may reduce cervical cancer disparities in the Delta. In a broader scope, the Appalachian Community Cancer Network has successfully addressed cancer disparities in that region through interstate community-academic partnerships funded in part by the National Cancer Institute.26 Again, development of similar networks, but modified for region-specific resources and organization, may help facilitate the reduction of cancer health disparities across the Delta Region.

Limitations

These analyses have limitations. First, as this study is solely descriptive in nature, analyses did not control for relevant potential risk factors such as socioeconomic status, health behaviors, or cancer screening patterns that may affect mortality rates and comparisons across regions. Still, the data indicate a disproportionate cancer burden in the Delta Region compared with other regions, even for cancers not affected by screening (e.g., lung cancer, as data were collected before the new screening guidelines) or behavior (e.g., prostate cancer). Future research should examine the factors that contribute to these cancer disparities in the Delta Region. Furthermore, because the population in the Delta Region was primarily White or Black, rates for other racial groups were not calculated to provide a more precise and refined characterization of racial disparities.

Conclusions

Substantially disproportionate cancer incidence and poor outcomes were identified in the Delta Region. These disproportionately poor cancer statistics were most striking in Blacks and all residents of rural parts of the Delta Region. Higher rates were found in comparison with the country as a whole and compared with another socioeconomically disadvantaged region (i.e., Appalachia). These findings suggest that further research is needed to elucidate the causes of greater cancer burden in this region. Additionally, these disparities indicate that health behavior and screening initiatives and regional research and community partnerships may help ameliorate the cancer burden in this region.

Whitney E. Zahnd, Wiley D. Jenkins, and Georgia S. Mueller-Luckey

MS. WHITNEY E. ZAHND is a Research Development Coordinator in the Population Health Science Program/Center for Clinical Research at Southern Illinois University School of Medicine. DR. WILEY D. JENKINS is an Associate Professor in the Department of Family and Community Medicine and Science Director of the Population Health Science Program at Southern Illinois University School of Medicine. MS. GEORGIA S. MUELLER-LUCKEY is a Statistical Research Specialist in the Center for Clinical Research at Southern Illinois University School of Medicine.

For correspondence please contact Whitney Zahnd at Southern Illinois University School of Medicine, Center for Clinical Research, Population Health Science Program, 201 E. Madison St., P.O. Box 19664, Springfield, IL 62794-9664, Phone: 217-545-2428, Email: wzahnd@siumed.edu.

Acknowledgments

Wiley D. Jenkins is supported in part by a grant from the National Cancer Institute (1P20CA192987-01A1).

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