Traditional thinking holds that a woman is protected from heart disease and osteoporosis until she goes through menopause.
But new research with monkeys questions that belief, and suggests that the time to start protecting your heart and guarding against bone loss is during perimenopause, or preferably, even earlier.
"Most women think they don't have to worry much about chronic health problems until perimenopause or menopause. But there's a high-risk trajectory that women can get on in their reproductive years that sets the stage for later problems," said Jay Kaplan, head of the section of comparative medicine at Wake Forest University School of Medicine.
Kaplan said his hypothesis is that the quality of ovarian function in the premenopausal period can contribute to your health status later in life. He was scheduled to present his theory and a review of previous studies that support his hypothesis on Monday at the American College of Veterinary Pathologists annual meeting, in Boston.
"Ovarian function varies quite a bit during the premenopausal years," Kaplan said. "And it turns out that reproductive function in both women and monkeys is easily impaired by stress."
He said that women may not even realize their ovarian function is impaired, because they still may cycle normally. But that means these women are being exposed to varying levels of estrogen, which can have an effect on your heart and bone health, he added.
Perimenopause is the time leading up to menopause, which is defined as not having had a period for 12 months. During perimenopause, a woman's body starts making less of certain hormones, such as estrogen and progesterone, and she begins to lose the ability to become pregnant. Perimenopause can start as early as age 35, according to the U.S. National Women's Health Information Center.
In previous monkey studies that Kaplan had conducted, he found that stress reduced estrogen levels and began to cause the buildup of plaque in the blood vessels. Loss of estrogen also contributes to a loss of bone density.
Dominant monkeys, Kaplan said, harass subordinate monkeys continually. The constant stress caused by this harassment reduces estrogen levels in subordinate monkeys, and reduces their fertility levels as well, he said.
The same thing can occur in women in today's society, Kaplan added. But they often won't realize there's a problem unless they're having trouble becoming pregnant or sustaining a pregnancy, he said.
The good news, Kaplan said, is that this loss of estrogen is reversible if treated early on. One way to treat it is to reduce stress, though that isn't always possible. Another option is hormone treatment, he said.
Hormone therapy results from the Women's Health Initiative were disappointing -- the study found hormone-replacement therapy given to menopausal women could increase the risk of breast cancer, heart attack and stroke, rather than prevent illness. But Kaplan and others contend the trials should have been done on younger women.
In another monkey study, Kaplan treated estrogen-deficient monkeys with estrogen before they entered menopause. Doing this helped prevent plaque deposits from building up on blood vessel walls, thus protecting against cardiovascular disease.
Trials of hormone therapy on younger women are currently under way to see if early treatment of estrogen loss can help maintain cardiovascular health, according to Kaplan.
Dr. Steven Goldstein, an obstetrician/gynecologist at New York University Medical Center, and author of Could It Be Perimenopause?, said, "The reality is a lot of heart health begins before menopause."
"Perimenopause is an excellent opportunity to begin a self-assessment and medical report card. Develop a plan with your doctor for your overall health, diet and lifestyle for the second half of your life. Perimenopause is a critical time in women's health," he added.
Until more is known about the effects of earlier estrogen therapy, Kaplan said it's a good idea to try to reduce stress wherever possible.
"Stress does matter. In fact, it matters in ways that women probably don't recognize. Try to learn new coping skills for stress, and extend your social networks," he said.