Women who develop thick waists and high cholesterol at menopause may be at higher risk of heart disease because they also have more damage to their arteries, U.S. researchers reported.

They believe their findings may help explain why older women who took hormone replacement therapy had higher rates of heart attacks and strokes. They also may offer the possibility that younger women can safely take HRT if they want to.

Menopausal women who had more abdominal fat and higher cholesterol, already linked with heart disease, also appeared to be experiencing more oxidative stress, Kerrie Moreau of the University of Colorado at Boulder and colleagues reported.

Both circumstances are known to be linked with heart disease but this is the first time the two have been specifically linked to one another, Moreau said in a telephone interview.

"We know arteries become stiffer when we get older. We were trying to figure out why that is," Moreau said.

"One mechanism is the development of oxidative stress -- free radicals that can damage cells in our body. We were able to pinpoint what type of post-menopausal women this is associated with. Those women who have more body fat accumulation in the abdominal region appeared to have more oxidative stress."

After menopause many women undergo a shift in body fat so that there is more fat in the abdomen. This can cause the sympathetic nervous system, which controls blood vessel function, to become elevated and stiffen the arteries.

And because the women are no longer producing estrogen, a natural antioxidant, they begin to suffer from artery disease, Moreau proposed.

TESTING OXIDATIVE STRESS

Moreau and colleagues studied 31 healthy, sedentary women and found that the arteries of women past menopause were 56 percent less elastic than those of premenopausal women.

They tested oxidative stress by giving the women intravenous infusions of ascorbic acid -- better known as vitamin C and a powerful antioxidant.

When the postmenopausal women were given ascorbic acid, elasticity in their carotid arteries improved by about 26 percent, Moreau's team reports in the American Heart Association journal Hypertension.

Moreau stresses that the effects of the vitamin C are temporary and that the body quickly excretes the high levels used in her study.

What it may show is that estrogen therapy may help prevent some of this damage, if used before it happens.

"We can't say you should take estrogen," she stressed.

But several researchers have noted that the studies that were the basis of pulling millions of women off hormone replacement therapy included women with an average age of 65 -- well past menopause and perhaps suffering from already damaged arteries.

"Chances are the vessels are already aged and they could be getting stiffer," Moreau said.

"When we give hormone therapy to an unhealthy vessel, it can actually cause bad things to happen. So maybe if you initiate hormone therapy in a healthy vessel, right around the age of menopause, we could probably see some different things."

She agrees with others who want to investigate the possibility that HRT given to younger women, just going through menopause at 45 to 55, might prevent the damage. Some women who have severe symptoms such as hot flashes may opt for HRT, and watching their health years later may give an answer.