ANN ARBOR—Obesity is a risk factor for heart disease for people without other risk factors.

In a paper out today in the American Heart Association’s journal, Circulation, a group of researchers led by University of Michigan’s Patricia Peyser report the results of a 14-year study of coronary artery calcification in 443 white men and women. The amount of calcification was measured non-invasively using computed tomography (CT) scanners. Calcification is evidence of coronary atherosclerosis, which in turn is strongly associated with the risk of heart attack or death due to heart disease.

The study found that in those considered at lower risk of heart disease, obesity was significantly associated with the progression of coronary artery calcification.

The study linked measures of obesity, waist circumference, waist-to-hip ratio and body mass index, to the progression of coronary artery calcification in people considered at lower risk for heart disease, based on traditional risk factors like age, gender, cholesterol levels, blood pressure and smoking status.  

“We were surprised by the higher rate of progression of calcification in obese people in the lower risk group,” said Peyser, professor of epidemiology at the U-M School of Public Health. “We found that obesity increases the risk of coronary disease for people who have lower traditional risk factors.”

While some studies have looked at calcification of the arteries over a shorter term, the 14-year duration makes the team’s research unique, Peyser said. “The majority of studies look directly at obesity and the risk of having a heart attack. We took a step back and looked at the disease’s progression, before people got to that major event,” Peyser said. “We wanted to see if there are ways to predict who is at risk before the heart attack happens.”

“The important public health message is that prevention of obesity, as well as weight reduction in those already overweight, is important for people with an otherwise favorable risk factor profile for heart disease.”

She noted that when the research team began their work in 1991, only a few institutions had the computed tomography scanners to non-invasively assess calcification. Now, many institutions have CT scanners which are used to assess coronary artery calcification in clinical practice and in research studies.

The project evolved from the Rochester Family Heart Study, a collaboration between U-M and the Mayo Clinic since 1980. Peyser said additional research involving other ethnic groups is needed to better understand the relationship between calcification and heart disease.

“Progression of Subclinical Atherosclerosis: Does Obesity Make a Difference?” involved scientists at U-M and the Mayo Clinic: Andrea E. Cassidy, Lawrence F. Bielak, Yan Zhou, Patrick F. Sheedy II, Stephen T. Turner, Jerome F. Breen, Philip A. Araoz, Iftikhar J. Kullo, and Xihong Lin.

It is based on a $2.7 million, five-year research grant from the National Institutes of Health.

Related links:

The journal Circulation

Patricia Peyser

U-M School of Public Health