Mortality Disparities Are Rising as County Poverty Levels Increase

ACS researchers found that the difference in counties' death rates for all causes and 8 of the top 10 causes widened when poverty levels increased.

The Research

Researchers at the American Cancer Society (ACS) recently examined how death rates across the US (except for Alaska and Hawaii) differ by a county's poverty level. They evaluated the association between poverty levels and death rates across counties for all causes and for the 10 leading causes of death in 2020, and they published their results in the clinical and translational journal Med.

The top 10 causes of death that the researchers' focused, accounting for 96.7% of all deaths, were (listed from the condition causing the most deaths to the least):

1. Diseases of the heart, including coronary artery disease (caused from atherosclerosis, the buildup of plaque in the arteries that supply blood  to the heart), which can result in a heart attack; heart            failure; peripheral artery disease (narrowing or blockages in arteries that supply blood to the arms and legs); arrhythmias, and others.
   
   
2. Cancer
   
   
3. Diseases that affect blood flow to the brain (cerebrovascular disease), such as stroke, blood clots or artery blockage, narrowing of the blood vessels (stenosis), and a bulge in a blood vessel that may burst and cause bleeding (aneurysm)
   
   
4. Pneumonia/influenza
   
   
5. Unintentional injury, such as falls, motor vehicle accidents, poisoning, and drug overdose
   
   
6. Chronic obstructive pulmonary disease (COPD), a progressive lung disease that includes emphysema and chronic bronchitis.
   
   
7. Alzheimer’s disease
   
   
8. Type 2 diabetes
   
   
9. Suicide
   
   
10. Kidney disease

The research team looked at death rate changes for two timeframes—1990 through 1994 and 2016 through 2020 (minus the time affected by COVID-19).

They defined the highest and lowest county poverty levels by the proportion of residents with yearly incomes lower than the Federal Poverty Level (FPL): 

• Counties with the lowest level of poverty had less than 10% of residents with incomes below the FPL.
  
  
• Counties with the highest level of poverty had 20% or more of residents below the FPL. 

As an example, the FPL was an income of $26,200 a year for a family of 4 in 2020. 

Here are some of their key findings.

Improving Death Rates

The death improved/declined across all poverty levels and US counties from 1990 through 1994 and from 2016 through 2020 for all causes and for 4 of the leading causes of death: diseases of the heart, cancer, cerebrovascular disease, and pneumonia/influenza.

Improvement in death rate was better in counties with lower levels of poverty. Because there was less improvement in death rate in counties with higher levels of poverty, the disparity in death rates widened between counties with the highest and lowest poverty levels.

The improvement in death rate for all causes had substantial geographic variations. The largest improvements in death rate were concentrated along the East and West coasts and several areas of the northern US. The smallest improvements were in the Midwest, Appalachia, and parts of the South—areas where multiple counties have the highest poverty levels.

Death rates for heart diseases and cancer had the smallest improvements in the South and Midwest.

Pneumonia/influenza had the smallest improvements along the Mississippi Valley and in the Great Plains. 

Worsening Death Rates

The death rate increased/worsened across the nation from 1990 through 1994 and 2016 through 2020 for the 6 other leading causes of death: unintentional injury, COPD, Alzheimer's disease, Type 2 diabetes, suicide, and kidney disease.

The effect of poverty levels on these conditions was mixed. For COPD and type 2 diabetes, death rates improved in counties with the lowest poverty level, but death rates worsened in counties with the highest poverty levels.

Overall, death rates worsened the most for unintentional injury and Alzheimer's disease at all poverty levels studied. For unintentional injury, worsened death rate may largely be due to the ongoing opioid crisis in the US. For Alzheimer's disease, worse death rates may be due in part to aging of the population and also increased reporting of dementia as a cause of death.

Death rates for certain conditions varied by sex. For  females, the death rate improved for all income levels studied for Type 2 diabetes. For males, the death rate improved at all the studied income levels for COPD.

Disparities in Death Rates

Some conditions had worse disparities than others. The largest increases in disparities in death rates between counties with the highest and lowest poverty levels were for type 2 diabetes, pneumonia/influenza, COPD, kidney diseases, and diseases of the heart.

The prevalence of certain risk factors in an area are associated with disparities for condition and county poverty level. The South has a higher prevalence of smoking (a risk factor for cancer, cerebrovascular disease, COPD, and diseases of the heart) and obesity (a risk factor for multiple types of cancer, cerebrovascular disease, diseases of the heart, kidney disease, and Type 2 diabetes). Several Southern states have also not expanded the income levels to qualify for Medicaid, and Medicaid has been linked greater improvement in death rates.

The study authors were ACS researchers in Cancer Surveillance & Health Equity Science: Daniel Wiese, PhD; Hyuna Sung, PhD; Ahmedin Jemal, DVM, PhD; and Farhad Islami, MD, PhD.

Why It Matters

The data from this study may be a catalyst for more research about the factors that affect the relationship between poverty and changes in death rates to find effective interventions to reduce inequities between populations.

More insights can help the nation's health to improve and premature mortality to be reduced, especially in counties with residents living with the highest levels of poverty.