Psychosocial factors, such as cynical distrust, chronic stress and depression, may be associated with higher levels of inflammatory markers measured in the blood, which in turn are related to an increased risk for cardiovascular disease, according to a report in the January 22 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
A number of studies have linked psychosocial characteristics with cardiovascular disease and death, according to background information in the article. However, the mechanisms by which they are related are unclear. "Research has highlighted the importance of inflammation in the initiation and development of atherosclerosis and in the precipitation of cardiovascular events," the authors write. "Inflammation may be a mechanistic pathway linking psychosocial factors to cardiovascular disease."
Nalini Ranjit, Ph.D., of the University of Michigan, Ann Arbor, and colleagues used data from the Multi-Ethnic Study of Atherosclerosis, a study of 6,814 men and women who were between the ages of 45 to 84 years (average age 62.2) when they enrolled, between 2000 and 2002. Participants filled out a questionnaire with demographic information, and several separate questionnaires that assessed the psychosocial risk factors of depression and chronic stress. Cynical distrust was measured at a follow-up visit between 2002 and 2004. Blood samples obtained at the initial examination were analyzed for IL-6, C-reactive protein and fibrinogen, all markers for inflammation.
The researchers found graded associations between all three psychosocial factors and inflammatory markers. "The strongest and most consistent associations were observed for cynical distrust, which was positively associated with all three inflammatory markers," the authors write. "Chronic stress was positively associated with the IL-6 level and had a moderately positive association with the CRP level, whereas depression was associated only with the IL-6 level."
"Associations of psychosocial factors with inflammatory markers were reduced by 20 percent to 55 percent after adjustment for behavioral factors and by 45 percent to 100 percent after adjustment for body mass index (BMI) and diabetes, mostly owing to the effect of BMI," they continue. "No associations remained after controlling for socioeconomic position, behaviors, BMI and diabetes."
According to the authors, this suggests that at least part of the link may be due to the mediating role of behaviors--for instance, psychosocial factors may increase the chance that an individual takes up behaviors such as smoking, which results in higher levels of inflammatory markers. Stress and psychosocial factors may contribute to obesity and related metabolic problems, thus explaining the weakening of the association after controlling for BMI and diabetes. In addition, "socioeconomic position is likely to be an antecedent to psychosocial characteristics, as well as to other factors (e.g. behaviors, BMI and diabetes) associated with inflammation," the authors write. However, further studies are needed to determine the nature of the relationship between inflammation and these mediating factors..
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