Inflammation key factor in low socioeconomic status link with CVD

Inflammation key factor in low socioeconomic status link with CVD

By Caroline Price

22 November 2007

Circulation 2007; 116: 2383-2390

MedWire News: Low socioeconomic status is linked to increased levels of serum inflammatory markers, which may explain why it is associated with higher rates of cardiovascular disease (CVD), according to a report in the journal Circulation.

The study of over 6000 men and women revealed that lower income was associated with higher concentrations of interleukin (IL)-6, and C-reactive protein (CRP) in several race and ethnic groups.

"This study helps to explain some of the puzzle as to why poor people have more heart disease," commented Nalini Ranjit (University of Michigan, Ann Arbor, USA), who led the study group.

The researchers reviewed data on 6814 US adults aged 45 to 84 years in the Multi-Ethnic Study of Atherosclerosis (MESA). They conducted race- and ethnicity-stratified analyses to estimate the associations of household income and education with IL-6 and CRP before and after adjustment for factors such as infection and medication use, psychosocial factors, behaviors, adiposity, and diabetes.

Household income was inversely associated with levels of the markers in all race/ethnic groups. Each standard-deviation decrease in income, the equivalent of around US$40,000 (€27,000), was associated with between 6% and 9% higher IL-6 and CRP levels, with the greatest increase in risk among White individuals.

By contrast, the association between education and income was inconsistent across race/ethnic groups. Each standard-deviation decrease in education level was associated with 6-14% higher levels of IL-6 and CRP in White and Black groups, whereas no association was seen for Chinese and Hispanic populations.

"When we adjusted the model for other possible confounding markers such as infection, there was no significant effect on the findings," Ranijit noted. "But when you look at body mass index, it shrinks the effect of income or education on IL-6 and CRP, meaning the associations are mediated by adiposity."

Other factors contributing to the observed associations included a generalized attitude of cynical distrust, which explained some of the link between education and IL-6 levels in all groups, and smoking, which partly accounted for this association in Black and White populations.

"Our results suggest that persons of lower socioeconomic position have greater inflammatory burden that those of high socioeconomic position as a result of the cumulative effects of multiple behavioral psychosocial and metabolic characteristics," the authors write.

"If the role of inflammation in causing multiple chronic diseases is confirmed, inflammation may represent a common element through which low socioeconomic position is related to CVD and other chronic diseases of aging."

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