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Switching on sleep
Light, hormonal changes may affect how women sleep

by Sue Dremann

Dr. Kin Yuen spoke before a packed room of sleep-deprived women, recounting her own bout with sleeplessness. It came during her pregnancy.

"I was a zombie," she said.

Yuen, the medical director of the Bay Sleep Clinic in Menlo Park, spoke recently at the Littlefield Women's Health Public Forum. The forum is a free monthly lecture series on women's health issues sponsored by Women's Health at Stanford.

Chronic sleep deficit affects 40 percent of American adults — to the degree that sleepiness interferes with their daily activities, according to the Stanford Hospital & Clinics Sleep Disorders Center.

Until recently, 75 percent of sleep-related research was conducted on men, according to the National Center on Sleep Disorders Research. But sleep studies in the last five years have increased for women.

There are important sleep-related physiological differences in women, including the timing of nocturnal growth-hormone secretion and different brain-wave activity through the night, according to the center.

Researchers are just beginning to understand the differences sleep plays in normal development, maturation, aging and disease propensity. Sex hormones influence sleep and circadian rhythms, and sleep affects neuroendocrine function, which could potentially have different effects on behavior, the center noted.

The female sex is a risk factor for insomnia, and insomnia is a risk factor for depression, the report noted.

The cumulative effect of repetitive insomnia that can occur every month for 40 years in a woman's life are not known, according to the Sleep Disorders Center.

But Yuen said a Harvard study on nurses who worked swing and graveyard shifts showed an increase in breast and colorectal cancers and cardiovascular disease. Those nurses had a breast-cancer rate 1.5 times above the average. Long sleepers — who are making up for sleep deficits due to insomnia, work schedules or underlying sleep disorders — had a higher incidence of mortality, she added.

Premenstrual syndrome is associated with significantly disturbed sleep quality, according to the National Center on Sleep Disorders Research.

Sleep disturbances during menstruation, particularly during the first two days, occur when there is a fall in progesterone or sensitivity to hormonal fluctuations that occur each month, according to Yuen. As the body retains fluid, airway resistance increases, making it harder to breathe. Women with sleep apnea or asthma also have more problems.

During pregnancy woman experience different sleeping patterns. A flood of progesterone during the first trimester can cause swelling, congestion and breathing irregularities, she said. Women tend to sleep more in a 24-hour period to make up for the lack of quality sleep.

In the second trimester, the total hours of sleep become more normalized, but one in five women still have sleep difficulties during slow-wave sleep, the period when the body rejuvenates itself, she said.

But in the third trimester, the sleep pattern changes. More fragmented sleep occurs, especially during deep sleep or REM, Yuen said.

Certain sleep disorders, such as restless-leg syndrome, periodic limb-movement disorder, sleep apnea and insomnia may emerge during pregnancy. The extent to which they may place women at higher risk later in life are not yet known, the report noted.

Thirty percent of pregnant women begin snoring for the first time during the second trimester. Pregnant women who snore have a two-fold greater incidence of hypertension, pre-eclampsia and fetal growth restriction compared to non-snorers, according to the report.

Among peri-menopausal and menopausal women, many complain of sleep disturbances. Estimates of self-reported menopausal-related insomnia range from 33 to 51 percent, according to the Center on Sleep report.

Hot flashes are often associated with why women wake up at night during peri-menopause, but that isn't definitive. Many women are also waking up who don't have hot flashes. Sleeplessness is now thought to occur due to fluctuations, rather than a drop, in estrogen, Yuen said.

Yuen said evidence is mounting for the protective quality of melatonin, the chemical that helps induce sleep. Melatonin may protect against abnormal cell growth. And sleep may not just be regenerative. Researchers are finding the same inflammation markers in sleep-deprived women as in those with cardiovascular disease. And REM sleep has an important function in memory. When REM is deprived, cognitive function is impaired, Yuen said. Researchers are beginning to look at a possible correlation between reduced REM sleep and diseases such as Alzheimer's she said.

For the chronically sleep deprived, Yuen recommends being evaluated to rule out depression and anxiety. Once that is ruled out, for some people, melatonin supplements may help. Much is not known about the safety and efficacy of herbal preparations, she said. And there are concerns about disease risks from hormone-replacement therapy.

Yuen sees many Silicon Valley retirees who got off the clock and lost track of their sleep patterns. Yuen helps patients reset their body clocks by changing their bed time one hour per week for a month. And she has patients add to their daily light exposure.

A light-receptive layer outside the brain acts like a light switch, turning on chemicals necessary for wakefulness, such as dopamine and ephedrine, she said. Cells responsible for releasing melatonin, which causes sleepiness, shut down when exposed to evening light. Strong light sources from televisions and even bathroom lights can trigger the switches and flood of chemicals that keep patients awake, she said.

For night owls, Yuen recommends limiting strong light exposure to no later than 9 or 10 p.m. Patients expose themselves to sunlight upon waking for 45 minutes to an hour, using either natural light or a light box.

Patients who go to bed at 8 p.m. and wake up at 3 a.m. receive light one hour before bedtime.

"Let the melatonin secretions carry you off to sleep," she said.

Staff Writer Sue Dremann can be e-mailed at sdremann@paweekly.com.