Stress links poverty to inflammation, heart disease
At a glance
- Researchers found that people with lower incomes had more stress-related brain activity, which was linked with greater inflammation in the body.
- Those with more inflammation had a higher risk of heart attack and other heart problems over the following years.
- This stress-driven inflammation may account for almost a third of the increased risk of heart disease in people with lower incomes.
Poverty can take a toll on health. People with lower incomes have a higher risk of many diseases, including heart disease, diabetes, and cancer. Some of this risk is driven by reduced access to health care. Lifestyle factors also play a role. For example, people with lower incomes have higher rates of smoking. But after accounting for such factors, extra unexplained risk remains.
Researchers have proposed that the body's stress response may link poverty with disease risk. Long-term stress can increase inflammation in the body. Chronic inflammation is thought to play a role in the development of many health conditions.
In a previous study, researchers led by Dr. Ahmed Tawakol from Harvard Medical School used PET imaging to scan the bodies and brains of almost 300 people without known heart disease. They measured brain activity in an area called the amygdala, which helps regulate the body's stress response. They also looked for markers of inflammation in immune cells and arteries.
That study found that people with higher levels of stress had increased activity in the amygdala and more inflammation in their arteries. They also had a higher risk of having a major cardiovascular event such as a heart attack or stroke over the next several years.
In follow-up research, Tawakol and his colleagues looked at the contribution of income to this inflammatory pathway. They focused on 289 of the study participants who had their current address recorded. The researchers used data from the U.S. Census to gather average neighborhood income for each participant. They then added this information to their model. The study was funded in part by NIH's National Heart, Lung, and Blood Institute (NHLBI). Results were published on July 2 in the Journal of the American College of Cardiology.
People who lived in lower-income neighborhoods had higher levels of stress-related activity in their amygdalas. The increased amygdala activity was associated with greater inflammatory cell production in bone marrow and more inflammation in arteries.
The participants living in the lowest-income neighborhoods had four-fold greater risk of a major cardiac event over the next five years than those living in the highest-income neighborhoods. This risk was about three- to six-fold higher after adjusting for smoking, obesity, other known cardiovascular disease risk factors, and access to health insurance.
The team calculated that this pathway linking the brain to inflammation could account for 28 percent of the total effect that poverty has on the risk of heart disease.
"These observations point to a mechanism that may be an attractive target for future therapies aimed at reducing disparities in health outcomes," Tawakol says.
The methods used in the study can't directly show that stress caused by poverty led to the observed increase in heart disease risk. Further research is needed to understand the factors that trigger this inflammatory response and test potential interventions.
-by Sharon Reynolds
For further information on this and other health topics, visit the web site of the National Institute of Health at www.nih.gov.