Salary, Schooling, Inflammation Linked

Nov. 19, 2007 -- The blood may hold chemical clues about the relationship between income and health.

A new study shows that people with lower incomes and fewer years of formal education tend to have higher blood levels of two inflammatory chemicals.

High levels of those chemicals -- interleukin-6 (IL-6) and C-reactive protein (CRP) -- have been linked to heart disease.

It's not that a person's salary or schooling determines their health. But education and income often sync up with a person's opportunities, access to medical care, and other factors.

In the new study, the University of Michigan's Nalini Ranjit, PhD, and colleagues measured IL-6 and CRP levels in some 6,800 U.S. men and women aged 45-84.

Data included participants' education, income, BMI ( body mass index, which relates height to weight), waist circumference, smoking, drinking, physical activity, diabetes, and medications.

Participants also rated their depression, hostility, and chronic stress.

In all of the groups studied -- white, African-American, Chinese, and Hispanic -- lower incomes were linked to higher levels of IL-6.

In whites and African-Americans, lower levels of education were linked to higher levels of IL-6.

The patterns were similar for CRP, Ranjit's team reports.

Being overweight was the most common link between education, income, and higher levels of IL-6 and CRP.

But it wasn't just about weight. Hostility and smoking also mattered. There may be multiple factors that connect increased inflammation and lower income, according to the study.

The study doesn't show how participants' inflammation and health fared over time.

The results appear in tomorrow's edition of Circulation.