Just a few years out of graduate school, Robert Wood Johnson Health & Society Scholars Allison Aiello, Ph.D., and Jennifer Dowd, Ph.D., have an ambitious goal: To work together to “pave the way for a new understanding of how socioeconomic status gets under the skin,” Aiello explains, “to discover how it affects health and the susceptibility to disease in later life.”
For decades, researchers have attempted to clarify the well-established connection between certain social determinants of health and disease. Aiello, an assistant professor of Public Health and Epidemiology at the University of Michigan School of Public Health (Scholar 2003-2005) and Dowd, an assistant professor of Public Health and Demography at Hunter College School of Health Sciences at the City University of New York (Scholar 2006-2008), have combined their expertise to advance our knowledge of social epidemiology by trying to explain why—in the most straightforward biological sense—poverty and associated conditions have such an impact on long-term wellbeing.
The Role of Latent Pathogens
In their research, Aiello and Dowd discovered a previously unknown factor that appears to play a key role in the development of cardiovascular disease, dementia and other illnesses—the impact of latent infections on the immune system. “We are trying to identify the actual mechanisms that connect certain conditions and we’ve been the first to show that a high immune response to certain pathogens, acquired early in life, causes the immune system to end up in a complex interplay with specific viruses causing inflammation and possibly higher rates of certain diseases,” Aiello said.
“Economists have not really looked at biological processes,” Dowd said. “Economic data on health is generally based solely on mortality data. I’m working on this approach because I think you need more than that to come up with effective economic policies related to health.”
Aiello and Down look first at the burden of multiple, common infections generally thought to be benign throughout life, specifically cytomegalovirus (CMV) and herpes simplex I. They, and other members of their research teams, found that people with lower levels of education had significantly higher immune responses to these viruses. Their study, “Socioeconomic Gradients in Immune Response to Latent Infections,” published in the American Journal of Epidemiology in 2007, was the first to show the relationship between socioeconomic status and a marker of cell-mediated immunity.
The following year, Aiello and Dowd discovered a similar connection between latent infections, socioeconomic position and cardiovascular disease; their work, “Persistent Pathogens Linking Socioeconomic Position and Cardiovascular Disease in the U.S.,” was published in the International Journal of Epidemiology. Further research by the team would reveal associations between latent infections and atherosclerosis, dementia and asthma.
“Overall, what we’ve found is that if you’re living in poverty, you have poorer immune function,” Aiello said, and therefore a more difficult time battling disease. “We looked first at CMV because it’s so prevalent in the population and it was thought to be so benign that it would only cause disease in infants or people with suppressed immune systems. Instead, we found these infections were disproportionately prevalent in groups with lower socioeconomic status from childhood, keeping their immune systems in a persistent interaction with the viruses, causing an immune cascade and inflammation.”
“A lot of these infections were also not necessarily associated with lower socioeconomic status,” Dowd adds. “So now we want to learn how these infections are getting transmitted at such high rates so early in life in these populations.” She also noted that many prevailing explanations, such as the impact of stress hormones on people of lower socioeconomic position, do not fully explain the phenomenon. “We now have an exploratory grant from the National Institutes of Health to push forward, to try and make the links and find out what types of economic and social factors are involved, including things like housing prices and job loss,” Dowd said.
Dowd and Aiello discovered their mutual research interests and decided to work together when they met through the Health & Society Scholar program. “I became Jen’s mentor,” Aiello recalls, “I wanted to work with someone with her background in social science and economics,” she says. Dowd has also conducted research on economic inequality and the markers of stress.
“We are thinking about the public health implications for this work,” Aiello says. “We now have more targets for prevention, possibly vaccination or addressing multiple factors on many levels.” While Dowd and Aiello’s previous studies have focused on specific population groups, their latest research will be the first to look at the pathogen burden in the U. S. population. Their next article, “Socioeconomic Differentials in Immune Response in the U.S,” will be published in an upcoming issue of the journal, Epidemiology. “Together, our research examining infection and immune-response has filled important gaps in understanding the role that socioeconomic determinants play over the life course in creating and sustaining disparities in infection and ultimately, related chronic disease outcomes,” Aiello said. Their new study continues this trend.
In 2001, the Robert Wood Johnson Foundation created the Health & Society Scholars program to produce leaders in the field of population health who would focus on understanding the interconnected roles of biology, behavior, environment, economics and other social factors and health. Each year, the program accepts 18 scholars. As of 2008, 109 scholars had participated.