Improvements in colorectal cancer mortality rates are concentrated in the northern part of the United States, while southern states continue to fall behind, according to a report in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
Ahmedin Jemal, D.V.M., Ph.D., vice president for surveillance research at the American Cancer Society, said the decrease in death rates ranged from about 37 percent in Massachusetts to no reduction in Mississippi.
"This was very surprising, because when you look at the differences in reductions by state they are huge," said Jemal.
Although colorectal cancer remains the third leading cause of cancer mortality for men and women, rates have been declining nationwide for several decades. The researchers analyzed the temporal trend in age-standardized colorectal cancer death rates for each state from 1990 to 2007.
Overall, states in the South had a lower reduction in mortality than states in the North. The researchers found a strong correlation between higher rates of screening and higher reductions in rates of mortality by state. They speculate that economic disparities may be playing a role in rates of screening. In Mississippi, 18.8 percent of people do not have health insurance, compared with 5.4 percent in Massachusetts. More than 20 percent of the population of Mississippi lives below the poverty line, compared with a national average of 13 percent.
Elizabeth Jacobs, Ph.D., an associate professor of epidemiology and biostatistics at the University of Arizona, said the report shows a significant change in historical trends.
"It used to be that the highest rates of colorectal cancer mortality were in the northeastern part of the United States, but now we've really seen a switch," said Jacobs, an editorial board member of Cancer Epidemiology, Biomarkers & Prevention
. "It shows the importance of access to screening."