"We're not talking overt incidents. It's not racism in the form of being chased down the street because you have brown skin or being called a name," Lewis said. "We're talking about subtleties -- everyday insults that build up over time."
The women's scores over the years were averaged on a four-point scale, and in 2001 the participants underwent an examination known as a CT scan to measure coronary artery calcification -- buildup of calcium inside arteries that supply blood to the heart. It is considered an early stage of heart disease -- the nation's leading cause of death.
The more discrimination the women reported, the more likely they were to have calcification, the researchers found. After accounting for age, geographic location and education, the researchers found that for every unit of increase in perceived discrimination, the odds of having calcification nearly tripled. The chances of having calcification remained 2 1/2 times higher even after the researchers took into consideration such factors as high blood pressure, cholesterol, smoking, age and body weight.
"It's a strong association," Lewis said in a telephone interview before her presentation.
Although the study involved only women, it is likely the findings also would hold true for men, and possibly for other ethnic groups, as well, Lewis said. "We're seeing a real risk factor here."
Other research has suggested that chronic stress may increase the risk of heart disease by raising levels of stress hormones, such as cortisol, as well as boosting levels of inflammation in the body, Lewis said.
"We believe it's the accumulated burden of this subtle racial discrimination that's having this effect," Lewis said. "It's not just having this experience once or twice but having it over and over again throughout a person's life."
Other researchers agreed, noting that stress can also suppress the immune system.
"I think the findings clearly indicate that racism matters a lot," said David R. Williams, an expert on racial disparities in health at the University of Michigan at Ann Arbor. "A lot of people dismiss reports of discrimination as just something that's in people's minds. What these data suggest is these minor incivilities and minor incidents of discrimination are actually consequential for physiologic function, and adversely affect health."
Norman Anderson, the chief executive officer of the American Psychological Association who has done research in this area, called the research "groundbreaking."
"It's one of the first to link exposure to discrimination to a specific disease process," Anderson said.
But other researchers were skeptical, saying the researchers had failed, for example, to differentiate whether the women had actually experienced discrimination or just thought they had.
