Midnight hot flashes aren’t the only way that menopause disrupts women’s sleep, according to a new study. 

Researchers said women in perimenopause, the earliest stage of the menopausal transition, get less deep sleep and wake up more often in the week before menstruation. 

Menopause Sleep

The symptoms usually appear when a woman is in her late 40s, three to five years before the beginning of menopause. 

The findings were published today in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism.

Read More: Menopause Hot Flashes, Night Sweats Last for 7 Years for Many Women »

Changes in Body Affect Sleep

During perimenopause, women can have irregular menstrual cycles because of fluctuating hormone levels in their body. Younger women generally don’t experience changes in their sleep habits over the course of their menstrual cycle. 

Progesterone has a particularly powerful effect on sleep in the lead-up to menopause, according to the study.

"Menstrual cycle variation in hormones is one piece in the overall picture of sleep quality in midlife women," said a study author, Fiona C. Baker, Ph.D., of the Center for Health Sciences at SRI International in Menlo Park, California, and an honorary research associate at the University of the Witwatersrand in Johannesburg, South Africa. "This research can lead to a better understanding of the mechanisms behind sleep disturbances during the approach to menopause and can inform the development of better symptom management strategies."

Read More: 6 Tips for a Better Night’s Sleep »

How Sleep Was Studied

The researchers watched 20 perimenopausal women sleep in a laboratory twice each, once in the days before menstruation and once during the few days after menstruation.

Using an electroencephalogram to assess the women's sleep and brain activity, the researchers saw that the women enjoyed less deep sleep in the days before menstruation when their progesterone levels were higher. They also woke up more often and had more brief interruptions in sleep.

Eleven of the women had reported difficulty in sleeping at least three times a week for at least a month.

Read More: What You Can Do About Menopause Symptoms »