Counties Experiencing Persistent Poverty Have Higher Cancer Mortality Rates

Throughout the United States, counties experiencing persistent poverty have disproportionately higher rates of cancer mortality, according to a study published in Cancer Epidemiology, Biomarkers & Prevention.

In recent decades, advances in early cancer detection tests and treatment have contributed to lower overall mortality and higher survival rates. However, disparities persist across the cancer control continuum among individuals living in poverty. Increased exposure to carcinogens, low educational attainment, and lack of access to care all contribute to the association of individual-level poverty and substantial cancer risk.

“In addition, people living in poverty have high rates of cancers caused by occupational, recreational, or lifestyle exposures (eg, colorectal, laryngeal, liver, and lung) and by human papillomavirus infection (eg, anal, cervical, and oral),” the authors wrote.

Although cancer mortality has been found to be increased in counties with high levels of current poverty, less is known about mortality rates in counties which have experienced persistent poverty, defined as at least 20% of residents in poverty (below the federal poverty level) from 1980, 1990, and 2000.

Roughly 10% of all counties in the United States experience persistent poverty, and they are primarily located in the rural South. “Compared with other areas, persistent poverty counties have greater minority populations, more children under the age of 18, less formal education, and greater unemployment,” researchers said.

Investigators analyzed county-level data on cancer mortality from the National Center for Health Statistics collected between 2007 and 2011. Mortality rates were calculated as number of deaths per 100,000 people. For breast and cervical cancers, rates were calculated per 100,000 women; for prostate cancer, rates were calculated per 100,000 men.

Counties were classified as experiencing current poverty based on American Community Survey 5-year estimates. Sample t tests and multivariate linear regression were used to assess mortality by persistent poverty and compare rates with counties experiencing current poverty.

A total of 395 counties were classified as experiencing persistent poverty, encompassing 20,668,552 residents, while 871 counties were classified as experiencing current poverty between 2007 and 2011.

Analyses revealed:

• Overall cancer mortality was 179.3 (standard error [SE] = 0.55) deaths/100,000 people/year in nonpersistent poverty counties and 201.3 (SE = 1.8) in persistent poverty counties (12.3% higher; P < .0001).
• Cancer mortality was higher in persistent poverty vs nonpersistent poverty counties for overall cancer mortality as well as for several type-specific mortality rates: lung and bronchus, colorectal, stomach, and liver and intrahepatic bile duct (all P < .05).
• Among counties experiencing current poverty, those also experiencing persistent poverty had elevated mortality rates for all cancer types as well as lung and bronchus, colorectal, breast, stomach, and liver and intrahepatic bile duct (all P < .05).
• Median household income was almost one-third lower in persistent poverty counties (mean = $32,339; median = $32,156; interquartile range (IQR) = $28,705-$36,020] vs nonpersistent poverty counties (mean = $47,154; median = $44,745; IQR = $39,883-$51,440; P < .0001).

In addition to the impacts of limited access to care and social determinants of health, researchers noted that “people living in persistent poverty counties may have higher levels of chronic stress (due to factors such as insecure employment, adverse experiences, social isolation, etc) that could give rise to physiologic aberrations (eg, chronic inflammation) that result in elevated cancer incidence.”

The study was unable to account for residential history, marking a limitation, as researchers could not determine if the amount of time spent in a persistently poor county affected cancer mortality risk.

“To prevent health disparities, we need tools, people, and systems to ensure that everyone in this country has access to the tools they need to thrive, including socioeconomic opportunities, equity, and respect, as well as prevention resources and health care services,” said Jennifer L. Moss, PhD, a lead author of the study.

“We need interventions in these communities to change cancer-causing behaviors, to make cancer screening more accessible, to improve treatment, and to promote quality of life and survivorship.”

Reference

Moss JL, Pinto CN, Srinivasan S, Cronin KA, and Croyle RT. Persistant poverty and cancer mortality rates: an analysis of county-level poverty designations. Cancer Epidemiol Biomarkers Prev. Published online September 30, 2020. doi:10.1158/1055-9965.EPI-20-0007