Original Articles

By Dr. John Hart
Corresponding Author Dr. John Hart
Sherman College of Chiropractic, P.O. Box 1452 - United States of America 29615
Submitting Author Dr. John Hart

Mississippi, Rivers, Neoplasms, Geographic locations

Hart J. Cancer Mortality Rates And North-to-south County Position Along The Mississippi River: An Ecological Study. WebmedCentral EPIDEMIOLOGY 2010;1(10):WMC001088
doi: 10.9754/journal.wmc.2010.001088
Submitted on: 27 Oct 2010 06:32:42 PM GMT
Published on: 27 Oct 2010 09:42:21 PM GMT


Introduction:This study explores the relationship between north-to-south (N-S)geographic positions of counties along the Mississippi River and their cancer mortality rates for a single race.The research hypothesis is that cancer rates increase from N-S.
Methods: In this ecological study, archived age-adjusted cancer mortality data were obtained for counties along primarily the western border of the Mississippi River.Counties were numerically ranked from north-to-south with “1” representing the northern-most county and “47” for the southern-most county. Data analysis consisted of correlation and linear regression with the response variable = cancer mortality and the predictor variable = N-S position.
Results: A statistically significant relationship was observed between N-S county position and cancer mortality (Pearson: r = 0.568, p < 0.0001; linear regression: t = 4.63, p < 0.0001, parameter estimate = 0.661).
Conclusion: In this study, county positions were associated with cancer mortality rates to the extent that the mortality rates increased from N-S. Further research is indicated to explore possible mechanisms involved, such as income and diet.


The annual news by the United Health Foundation that typically reveals a southern state receiving the lowest health ratings, while a northern state typically receives the highest, e.g., in 2006 Minnesota #1, Louisiana #50, 1 prompted this writer to see if other states between Minnesota and Louisiana followed a N-S correlation. That analysis revealed a worsening of cancer mortality from N-S for states bordering the Mississippi River. 2-3 Analysis at the county level 4 however would seem more valid when assessing possible relationships between geographic position along the River and cancer mortality versus at the state level, since counties in a given Mississippi River state, e.g., a county on the eastern side of Tennessee, can be hundreds of miles away from the River.
The previous research at the county level, 4 though more relevant to analysis of the River, was confounded, among other variables, by the inclusion of all races, since different races can have different cancer rates, 5 and since the northern and southern regions of the United States have different race population proportions. Consequently, the present study includes only one race. The race selected was the largest population proportion so as to include more counties having reportable cancer mortality data by the National Cancer Institute (NCI) (too few counts results in no reporting for that county by NCI). Consequently, the white race was selected for the present study.
The purpose of this ecological study is to determine whether cancer mortality increases from N-S along the Mississippi River for a single race, under the following two similar theories: a) health status worsens from N-S, as evidenced by UHF reports and b) river water may be more polluted downstream, thereby possibly becoming a health risk to people using the River’s processed water for drinking. For item a, a literature search was performed in Google Scholar (on 9-22-10) using keywords “health disparities north versus south U.S.” but no relevant articles were found in the first two internet pages. For item b, keywords “health disparities along Mississippi River” were used, also in Google Scholar (on 9-22-10) and one somewhat relevant paper 6 was found within the first two internet pages. That study 6 found decreased life expectancy in the several areas in the U.S. including the area along the Mississippi River. However, no paper was found that studied the question of whether a health outcome, such as cancer mortality, gradually worsens along the particular pathway from north-to-south in the U.S.


From the National Cancer Institute’s databases, the following response variable was selected for counties along the Mississippi River: Annual age-adjusted cancer death rate averages per 100,000 persons, all cancers, white race, both genders, < age 65, for years 2003-2007. 7 The age of < 65 was selected to study the rates below the age of life expectancy. Counties primarily on the western border of the River were included in the present study. These counties belong to the states of, from N-S, Minnesota, Iowa, Missouri, Arkansas, and Louisiana (state map in Figure 1). The western River border counties were used in this study since eastern border counties along the River do not include the more northern counties in Minnesota. In Louisiana, the River “cuts” through (divides) the southern counties. The northern-most county (in Minnesota) was ranked as “1” while the second northern-most county was ranked as “2” and so on (example in Figure 2). Counties in Minnesota that are downstream yet actually located north (or east or west) of their upstream neighboring county, e.g., Beltrami county, were omitted from the study since the study focuses mainly on possible N-S effects and secondarily on possible downstream Mississippi River effects.
Data were analyzed in Excel (Microsoft Corp., Redmond, WA) and SAS 9.2 (Cary, NC). Two statistical tests were performed: Pearson correlation and linear regression. Two-tailed p-values < a Bonferroni-adjusted = 0.025 (traditional alpha of 0.05/2 tests) were considered statically significant.


Tests for normality in SAS for the cancer data were all > 0.05. Therefore the cancer variable was considered to exhibit sufficient normality as a prerequisite for the Pearson and linear regression procedures. Forty-seven counties were identified along the Mississippi River and their descriptive statistics are provided in Table 1. A moderate strength, statistically significant correlation was revealed between cancer death rates and N-S county position. That is, cancer death rates tended to increase from N-S (Pearson r = 0.568, p < 0.0001; R squared = 0.3231; Figure 3). In linear regression, the model utility p-value was < 0.0001, the parameter estimate = 0.66, t = 4.63, and p < 0.0001 (Table 2).


In this study, the linear regression findings suggest that position of a county is predictive (but not in itself causative) of cancer mortality rates. According to the parameter estimate 0.66, an increase of N-S position by 1 from N-S is expected to result in an increase in cancer mortality by 0.66 per 100,000 persons. This means that about one additional death per 100,000 persons is expected per county from north-to-south. Since there are 46 “jumps” (47-1) from county-to-county, from N-S in this sample, 46 x 0.66 = approximately 30 additional cancer deaths expected in the southern-most county compared to the northern-most county. Although this was not actually the case for these two counties located on the extreme ends of the N-S pathway, northern-most counties showed mortality rates in the 40s and 50s per 100,000 persons while some of the southern-most counties showed rates in the 70s, 80s and 90s per 100,000 persons.
Limitations to this study include the following: a) this is an ecological study, therefore causal inferences are not possible, and b) N-S position in itself would not be a causative factor, and that related factors, e.g., income, would more likely be causative factors.
The author was unable to find recent data on the concentration of potentially harmful materials in the Mississippi River at various N-S checkpoints. Even if hazardous content was found in the River, the drinking water itself, after being processed by the water companies, would have to be assessed before any type of conclusion on the possible role of downstream pollution might have.


In this study, cancer mortality rates at the county level rate increased from north-to-south along the Mississippi River. Further study is indicated to determine possible causative factors such as income and diet for these counties. Further study is also indicated to determine if other regions of the country exhibit similar north-to-south phenomena, or east-to-west, etc.  


A version of this paper was presented at the annual meeting of the Mississippi River Research Consortium, 2008, Dubuque, Iowa. 4


1. Associated Press. Healthy state report: Minnesota tops list, Louisiana ranks last. Foxnews.com. December 5, 2006. Available from: http://www.foxnews.com/story/0,2933,234543,00.html
2. Hart J. North-to-south position of Mississippi River states and their health rank.  Earth Science and Public Health: Proceedings of the Second National Conference on USGS Health-Related Research (pp. 20-1). U.S. Geological Survey. Edited by Buxton HT, Griffin DW, and Pierce BS. Scientific Investigations Report 2008-5022. 2008 (Apr 4). [Cited 2009 Aug 25]. Available from:http://pubs.usgs.gov/sir/2008/5022/
3. Hart J. Improved health correlated with ratio of chiropractors in Mississippi River states. Journal of Vertebral Subluxation Research 2007 (Dec 5):1-10.
4. Hart J. North-to-south position of counties along the Mississippi River correlated with selected outcomes. Proceedings of the Mississippi River Research Consortium. April 24, 25, 2008. Dubuque, IA. [Cited 2010 Sept 20]. Available from: http://mrrc.ngrrec.org/mrrc/mrrc.html
5. Albano JD, Ward E, Jemal A, Anderson R, Cokkinides VE, Murray T, Henley J, Liff J, Thun MJ. Cancer mortality in the United States by education level and race. Journal of the National Cancer Institute 2007; 99(18):1384-1394.
6. Ezzati M, Friedman AB, Kulkarni SC, Murray CL. The reversal of fortunes: trends in county mortality and cross-county mortality disparities in the United States. PLoS Medicine 2008; 5(4): e66. doi: 10.1371/journal.pmed.0050066
7. State cancer profiles. Death rates. [Internet]. National Cancer Institute. [Cited 2010 Sept 17]. Available from:  http://statecancerprofiles.cancer.gov/index.html

Table 2

Inferential statistics for counties along the Mississippi River selected for the present study. r = correlation coefficient. PE = parameter estimate. t = t value.

Pearson correlation between county position and cancer:         r = 0.568, p < 0.0001

Linear regression between county position and cancer:           PE = 0.66, t = 4.63, p = < 0.0001

Source(s) of Funding

No specific funding

Competing Interests



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