MINNEAPOLIS – Women with no history of sleep disorders often report sleep problems–especially difficulty falling asleep–as they undergo menopause. Their complaints were validated by a sleep study of more than 700 women presented at the annual meeting of the Associated Professional Sleep Societies.
“These data provide, for the first time, objective findings to support this common sleep complaint in postmenopausal women,” said Edward O. Bixler, Ph.D., vice chair of the sleep research division at Pennsylvania State University, Hershey.
To confirm the association between menopause and poor sleep and to seek a possible mechanism for this connection, Dr. Bixler and his colleagues conducted single-night polysomnographies on 715 women with a mean age of 49 years. Of these, 400 women were premenopausal, 120 were postmenopausal and using hormone therapy (HT), and 195 were postmenopausal but not using HT.
Women sleep as well as or better than men until they reach menopause, but sleep needs change with age, Dr. Bixler noted. With this fact in mind, the researchers used a group of 609 men who were at least 45 years old (with an average age of 49 years) as controls for the study. The average body mass index for both genders was 26.9 kg/m
The results of the single-night sleep test showed that the postmenopausal women who were not on hormone therapy took an average of 15 minutes longer to fall asleep compared with women on HT, and an average of 10 minutes longer to fall asleep compared with the men. These differences were statistically significant. The average time it took for the male controls to fall asleep was not significantly different from that of premenopausal women (a difference of 1.6 minutes) or of postmenopausal women who were taking hormone therapy (a difference of 5.6 minutes).
“What was unexpected was that we didn't find an increase in daytime sleepiness,” Dr. Bixler noted. He proposed that the lack of daytime sleepiness might be a result of the reduced need for sleep that is a natural part of aging. “As you age, you are less likely to be sleepy during the day even though you are sleeping less at night,” he said.
When the researchers looked at short-wave sleep, which is associated with the brain's ability to recharge, think, and remember, they found no differences between premenopausal women and male controls.
But postmenopausal women who didn't use HT were twice as likely to have slow-wave sleep as were male controls, and postmenopausal women who used HT were four times as likely to have slow-wave sleep as were male controls. Therefore, postmenopausal women who used HT were twice as likely to have short-wave sleep as were women who didn't use HT.
The data suggest that sleep latency is a valid symptom among menopausal women without a history of sleep disorders, especially among those who are not using HT. Based on these findings, menopausal women may be at increased risk for developing chronic insomnia that may require treatment, Dr. Bixler added.
“We would speculate that [menopausal changes] may be triggers for the onset of primary insomnia in vulnerable women,” he said.