Low-income adults are more likely to have very high levels of C-reactive protein (CRP), a risk factor for heart disease, according to a study led by researchers at the University of Southern California.
The study, published in the current issue of Brain, Behavior and Immunity, finds that among adults with income levels at or below the poverty line, 15.7 percent had very high levels of CRP, compared to only 9.1 percent of those in families above the poverty line.
"We have long known that poor people have worse health," said Eileen Crimmins, corresponding author and professor in the USC Leonard Davis School of Gerontology. "This paper provides evidence that people living at or near the poverty line are almost twice as likely to have very high CRP, which poses risks for long-term, chronic conditions like heart disease and cognitive loss. This may be one of the explanations for why poor people age faster."
CRP is produced as part of the immune response to inflammation. In healthy individuals, CRP levels return to normal after infection or injury subsides. However, some people have chronically elevated levels of CRP. Recent studies have shown high levels of CRP to be a useful predictor of heart disease.
Recent illness, chronic conditions and lifestyle account for some but not all of the explanations for the association between high CRP levels and socioeconomic standing.
"We found that even after accounting for various risk factors, people in poverty still had higher CRP," said Dawn Alley, another corresponding author and a recent doctoral graduate from the USC Davis School. "This suggests that even beyond issues like health behaviors and chronic conditions, there is something about poverty that makes people sick, and at least part of this effect is working through CRP."
The study also found that African Americans, Hispanics and women are more likely to have high levels of CRP, and that obesity is the largest contributor to above normal CRP levels.
The findings, which were funded by the National Institutes of Health, provide a better understanding about risk factors for poor health outcomes later in life.
The Division of Geriatrics at the UCLA School of Medicine also contributed to the study.