Death rates declined for almost all types of cancer over the study period, according to a team led by Ali Mokdad, PhD, of the Institute for Health Metrics and Evaluation at the University of Washington in Seattle (JAMA, January 24/31, 2017, Vol. 317:4, pp. 388-406). While the study did not speculate as to the reasons for the decline, researchers did track variations in cancer death rates at the county level, finding sharp regional differences in cancer mortality rates across the U.S.
Cancer is the second-leading cause of death, both in the U.S. and globally, and causes a significant economic burden. Cancer death rates have declined in the U.S. in recent years, as has been demonstrated in several studies, but there have been major variations in mortality between different regions.
Previous reports have only addressed cancer mortality in terms of regional variations at the state level, so the researchers decided to look into changes at the county level. In addition to providing more granular detail, this approach also matches up with public health efforts, which tend to be organized at the local level, the researchers noted.
The group analyzed death records from 1980 to 2014 from the U.S. National Center for Health Statistics (NCHS), as well as population counts from the NCHS, the Census Bureau, and the Human Mortality Database.
During the study period, there were 19.5 million cancer deaths. The U.S. cancer mortality rate fell from 240.2 deaths per 100,000 population in 1980 to 192.0 deaths in 2014, a decline of 20.1%.
The rate of decline in mortality rates varied by type of cancer, with testicular cancer showing one of the biggest drops, while death rates from kidney and non-Hodgkin lymphoma cancers showed no change.
|Rate of cancer mortality decline, by cancer type
|Colon and rectum
|Tracheal, bronchus, and lung
Bucking the trend was liver cancer, which actually experienced an 87.6% increase in mortality from 1980 to 2014, from 3.6 deaths per 100,000 population in 1980 to 6.8 deaths in 2014.
In the regional analysis, the researchers found that cancer mortality varied widely by county. Summit County, CO, had the lowest cancer mortality rate in both time periods, with a mortality rate of 130.6 deaths per 100,000 population in 1980 and 70.7 deaths in 2014. The deadliest county for cancer in 1980 was North Slope Borough, AK, with 386.9 deaths per 100,000 population in 1980, while in 2014 that dubious distinction was won by Union County, FL, with 503.1 deaths.
The distribution of higher cancer mortality also varied by disease type, with clusters of breast cancer in the southern belt of the U.S. and along the Mississippi River, while liver cancer deaths were more common along the Texas-Mexico border. Clusters of high kidney cancer mortality were found in North and South Dakota and in counties in West Virginia, Ohio, Indiana, Louisiana, Oklahoma, Texas, Alaska, and Illinois.
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