Trouble sleeping is common in women at menopause, or so conventional thinking goes. Yet the latest word is that it’s during perimenopause—the years leading up to menopause—when the trouble starts to brew. In fact, one in three perimenopausal women suffers chronic insomnia, according to data presented at the 2015 annual meeting of the North American Menopause Society.
Genetic factors may partly explain why insomnia is more common in women than in men. But hormonal changes during perimenopause and later in life are often cited as a more proximal cause of sleep problems that occur in midlife and older women. Here are some details.
During perimenopause, levels of estrogen, progesterone, and other hormones of the reproductive system are in flux. Estrogen production, in decline overall, is wildly erratic. Progesterone secretion stops during menstrual cycles when no ovulation occurs. Fluctuating levels of these and other reproductive hormones are often cited as factors underlying perimenopausal symptoms: irregular and heavy periods, headaches, and hot flashes.
Up to 80 percent of perimenopausal women experience hot flashes. For years women have reported that hot flashes cause night sweats and wake-ups, but only recently has the extent of the sleep disruption shown up in objective testing.
In a study published in 2013 in the journal Sleep, researchers set out to mimic perimenopause by injecting young women with a synthetic hormone that would suppress secretion of estradiol (a form of estrogen). Sixty-nine percent of the women went on to experience hot flashes (called vasomotor symptoms, or VMS, in medical lingo). The researchers hypothesized that nighttime VMS would lead to increased sleep fragmentation—and this is exactly what happened. “The number of nighttime VMS correlated directly with the degree of sleep disturbance,” the investigators concluded.
In another study, published this month in Psychoneuroendocrinology, researchers compared perimenopausal women with insomnia to perimenopausal women without insomnia and this is what they found, as measured by polysomnogram:
- Insomniacs got an average of 43.5 minutes less sleep than women without insomnia.
- Insomniacs were more likely to have hot flashes, and the number of hot flashes predicted the number of awakenings they had.
Hot flashes and night sweats are clearly disruptive to sleep and may increase midlife women’s vulnerability to insomnia.
Which Hormones Are Involved?
Hormonal fluctuations may give rise to both hot flashes and disturbed sleep during the menopausal transition. Estrogen is likely involved, since estrogen replacement therapy (less commonly recommended now than in the past) mitigates these perimenopausal symptoms. But there’s little agreement yet as to which hormonal factors are involved in midlife insomnia.
Researchers at the University of Washington recently analyzed data from the Seattle Midlife Women’s Health Study to see how hormonal factors correlated with the severity of perimenopausal symptoms. Compared with women with moderate and low levels of symptoms, women with severe hot flashes and moderate sleep disturbance
- had lower estrogen levels and higher levels of follicle stimulating hormone (released in the days leading up to ovulation to stimulate the growth of follicles in the ovary)
- tended to have lower levels of epinephrine (or adrenaline) and higher levels of norepinephrine. Epinephrine and norepinephrine are stress hormones.
But other research teams have come up with different results. Here’s what researchers publishing this year in the Journal of Clinical Endocrinology and Metabolism found:
- Estradiol (a form of estrogen) was protective of stable sleep in women ages 18 to 27. But there was no correlation between levels of estradiol and sleep quality in perimenopausal women.
- In perimenopausal women without sleep complaints, increased levels of follicle stimulating hormone did correlate with increased wakefulness at night. Not so in perimenopausal women with insomnia, in whom sleep duration correlated instead with anxiety and depression.
While hormonal fluctuations that occur during perimenopause can undoubtedly interfere with women’s sleep, the actual mix of hormonal factors underlying midlife insomnia is still unknown.
Melatonin and Older Women’s Sleep
One hormone that may be a factor in the sleep problems of older women is melatonin. Studies of young and middle-aged subjects have shown that women tend to have higher melatonin levels than men.
But results of a cross-sectional study of 528 older people showed that the opposite is true for older women. Investigators found that older women excreted 18.4 percent less melatonin in their urine at night than older men. This suggests that some older women may be deficient in melatonin. Unlike younger insomniacs, for whom melatonin supplements often have no effect, older women with insomnia may find that melatonin supplementation improves their sleep.