Does Estrogen Affect Older Women’s Sleep Disorders?

Despite questions about the usefulness of estrogen replacement therapy as a way to reduce the risk of heart disease in women, scientists want to know just how the powerful hormone affects the sleep, body temperature, and memory of women after menopause.

The “Siesta Study” at the University of Washington in Seattle will attempt to provide answers to those questions and some clues to how estrogen can be used to improve the quality of life of older women. It’s not uncommon for women in their mid-50s and older to experience sleep disorders, shifts in body temperature, and memory loss: Could estrogen help?

“We want to know how estrogen affects those areas of functioning–especially sleep,” says Karen Moe, PhD, a sleep researcher with the University of Washington School of Medicine. “Several studies show that estrogen replacement therapy improves sleep by reducing the number and duration of nocturnal awakenings, shortening the latency to sleep onset, and increasing REM [deep] sleep.”

Sleep’s Missing Link

But, Moe adds, there is a lack of scientific information about how the shifting hormonal balance of women after menopause affects sleep.

Specifically, the study will look at what Moe calls the “missing link” in a three-part linkage between estrogen levels, “system X” (which includes vasomotor symptoms and body temperature), and sleep.

The links between estrogen levels and system X and between system X and sleep are fairly well understood, but the relationship between estrogen levels and sleep is only guesswork until more research is completed.

“We want to find out whether estrogen affects sleep through a direct action on the brain or through an indirect effect through some other system,” Moe says. “The latter seems the more likely scenario. We also want to see if estrogen’s effects on the circadian body rhythms might affect sleep.” Circadian rhythms are the natural physiological responses of the body throughout the day-night cycle.

Approximately 100 nonsmoking women between 55 and 80 and at least 5 years past menopause will be enrolled in the 3-4-year study. The double-blind, placebo-controlled study will use a standard dose of 1 milligram of estradiol (an estrogen) and involve two 72-hour inpatient stays at the University of Washington Medical Center 6 months apart.

Screening for Heart Risks

“The volunteers are very carefully screened,” Moe says. “Those with preexisting heart disease are not allowed in. Also anyone with diabetes, a history of breast cancer, blood clots, major sleep problems, or excessive overweight will be excluded.”

Participants will keep sleep diaries and have their sleep patterns recorded and analyzed during visits to the medical center before and after taking either estrogen or placebo.

“We’ll also measure the effects of estrogen replacement on stress reactivity in women, as well as memory functioning,” Moe adds.

Participants will be given “mental challenges,” such as giving an impromptu speech before a group of people with only a few minutes’ notice, and then be tested for memory. Their blood cortisol levels (a hormone produced in response to stress) will be measured before, during, and after these tests. In addition, they will be asked to perform cognitive tests to see if estrogen does help improve memory, as experience with Alzheimer’s patients indicates.

“We know that when you give estrogen to older women, their cortisol levels and other hormonal stressors go down,” says Moe.

Risks Versus Benefits

Approximately 25,000 women participating in the federal Hormone Replacement Therapy trial to see whether estrogen replacement therapy actually reduces risk of heart disease in healthy, postmenopausal women learned recently that the treatment might temporarily increase the risk in certain circumstances.

It’s estimated that 10 million American women take an estrogen replacement drug to ease the symptoms of menopause, such as hot flashes, and to prevent menopause. The widespread belief that estrogen also protects against heart disease is not backed by scientific evidence, according to Michael Criqui, MD, an investigator in the federal study and professor of family medicine at the University of California, San Diego.

“There are risks associated with estrogen,” Moe says. “It’s a very powerful hormone. We need to do the basic research to get a better understanding of sleep in older women to know how estrogen affects all systems of the body, especially the brain. All of the measures in the Siesta Study are neurological markers.”

Another reason for looking into the role of estrogen in sleep may have a direct bearing on other aspects of health in older women.

Sedatives & Older Women

“Older women receive a disproportionate number of sedative-hypnotic prescriptions for sleep problems compared to older men,” Moe says. “Chronic sedative-hypnotic use can worsen already-poor sleep and lead to other effects from sedation, falls and subsequent fractures, and cognitive impairment.”

Perhaps correcting the hormonal imbalances that occur in many women with menopause can correct other problems, such as sleep disturbances, without resorting to other drugs that can have disastrous side effects, she says.

“A very large number of women are on estrogen replacement therapy,” Moe says. “Older women are increasingly being prescribed estrogen on a chronic basis to help reduce osteoporosis, cardiovascular disease, and possibly the risk of developing Alzheimer’s disease. “But much remains to be learned about the neurobiological effects of estrogen replacement therapy–including [how it relates to] sleep, temperature regulation, circadian rhythms, and stress reactivity.”

Article by: Robert Miskimon, Medical Writer

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