High level of heart fat may increase risk of coronary artery disease in postmenopausal women

Postmenopausal women who had greater volumes of paracardial adipose tissue (PAT) had a higher risk of coronary artery disease, according to an analysis of a longitudinal, community-based study.

The trial also found that greater volumes of epicardial adipose tissue (EAT) were significantly associated with a higher risk of coronary artery disease regardless of menopausal status, age, race and traditional cardiovascular disease risk factors.

Lead researcher Samar R. El Khoudary, PhD, MPH, BPharm, of the University of Pittsburgh Graduate School of Public Health, and colleagues published their results online in the Journal of the American Heart Association on Jan. 29.

The researchers mentioned that EAT is the fat that directly covers the heart and is the energy source for the heart, while PAT is fat that is outside of EAT and has no known heart-protective functions.

"For the first time, we've pinpointed the type of heart fat, linked it to a risk factor for heart disease and shown that menopausal status and estrogen levels are critical modifying factors of its associated risk in women,” El Khoudary said in a news release. “Clearly, epicardial and paracardial fat are distinct types of heart fat that are found to be greater in postmenopausal women for different reasons with different effects on heart disease risk—and thus should be evaluated separately when searching for ways to help women avoid heart disease.”

This trial, known as SWAN (Study of Women’s Health Across the Nation) Cardiovascular Fat Ancillary Study, enrolled 3,302 adults in 1996 and 1997 at study sites in Boston, Detroit, Oakland, Los Angeles, Pittsburgh, Chicago and Newark, New Jersey.

The women were 42 to 52 years old and had electron beam computed tomography scans performed at baseline to measure EAT and PAT. The researchers also used the C-150 Ultrafast CT Scanner from GE Imatron to measure coronary artery calcification (CAC).

The mean age of participants was 50.9 years old, while 38 percent were black, 58 percent were pre- or early perimenopausal, 10 percent were late perimenopause and 32 percent were postmenopausal. Participants with a CAC of 10 or higher were more likely to be older, postmenopausal and obese and had higher systolic blood pressure and body mass index.

The researchers found that EAT and PAT levels were significantly associated with greater odds of CAC presence after adjusting for age, race, study site and menopausal status. In addition, each 1-SD unit increase in log PAT was associated with a 102 percent higher risk of CAC presence and an 80 percent increase in CAC extent among postmenopausal women compared with pre- or early perimenopausal women.

Further, the association between PAT and CAC extent was stronger in women with lower estradiol levels, according to the researchers. They added that the association between PAT and CAC extent was dependent on estradiol levels and were menopause specific, while associations between EAT and CAC measures were not significantly modified by menopausal status.

“Our findings of significant associations of CAC measures with EAT volumes in women at midlife are in agreement with previous studies in other populations, which suggests a significant role of EAT in the pathogenesis of [coronary artery disease],” the researchers wrote. “Higher heart fat volumes are associated with [cardiovascular disease] risk factors, [cardiovascular disease] events and CAC.”

The researchers cited a few limitations of the study, including its cross-sectional design. The study also might not be generalizable to women of other ages or other racial and ethnic groups. In addition, they mentioned the findings of the extent of CAC and PAT should be interpreted with caution because of wide confidence intervals.

“Although greater volumes of EAT were significantly associated with CAC, only the association of CAC with volumes of PAT was dependent on menopausal status and [estradiol] levels,” the researchers wrote. “Our findings suggest PAT as a potential menopause-specific [coronary artery disease] risk marker and maintain that EAT and PAT are distinct fat depots that should be evaluated separately. The current study supports the need to monitor and target heart fat depots for intervention in women at midlife.”