High-frequency migraine headaches, which occur at least 10 days a month, are more common in women during the transition to menopause, according to a new study.

"For years women have been telling me as a headache doctor that their headaches worsen in perimenopause," but it hadn't been directly studied, said lead author Dr. Vincent T. Martin of the University of Cincinnati College of Medicine and co-director of the Headache and Facial Pain Program at the UC Neuroscience Institute.

Symptoms like hot flashes, irritability, insomnia and depression may start during the hormonal changes of perimenopause, when periods become irregular, but menopause does not officially begin until periods have stopped for one year.

"Since the average age of menopause is 51 to 52, and the average transition is five to 10 years, women may see a worsening of their migraines as early as 42 to 47 years old if they are going to have an average-age menopause," said North American Menopause Society executive director Dr. JoAnn V. Pinkerton. "The variability for normal menopause is 45 to 55, so women could see an intensification before or after that time."

Changes in brain chemicals may cause blood vessels to swell or dilate, putting pressure on nearby nerves and structures and causing a migraine, Pinkerton told Reuters Health by email.

"Hormonal fluctuations appear to act as triggers for migraines, although the actual mechanism is not known," said Pinkerton, who was not part of the new study.

Martin and his coauthors used data from a 2006 survey of more than 3,000 women ages 35 to 65 who experienced migraines before and during menopause and who self-reported headache symptoms and details of their menstrual cycles.

About 8 percent of women who were still having regular periods reported high-frequency migraines of more than 10 days per month. That rate rose to more than 12 percent of those in perimenopause and about 12 percent of postmenopausal women whose periods had stopped altogether, as reported in Headache: The Journal of Head and Face Pain.

Risk of headache was highest during late perimenopause, before periods stopped completely, when estrogen levels are low.

Women who have premenstrual symptoms earlier in life are likely to be hormonally sensitive and have a higher risk for migraines later, Martin told Reuters Health by phone.

"Probably in perimenopausal women it's strictly hormones, but in menopausal women there was a huge uptake in medications to treat headaches," Martin said. "If you start using a lot of these pain medications that might cause something called rebound headaches, which may be different."

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Depression rates increase during menopause as well, and women who are depressed may be more likely to report headaches as severe, he said.

During perimenopause, hormones can increase or decrease unexpectedly as the ovaries are "sputtering," he said.

"Every life event in a woman has the potential for changing migraines, including her first period, pregnancy and perimenopause," Martin said.

If hormones are triggering headaches, they may be moderated with birth control pills or a hormone estrogen patch, he said.

"Postmenopause, once hormonal fluctuations have diminished and hormone levels are consistently low and stable, the migraines often improve or stop," Pinkerton said. "Hormone therapy given for hot flashes may worsen or improve migraines."

"Migraines are one of the most common causes of disability in the workplace of any disease," Martin said. "If your headaches are occurring more than 15 days per month, if you're using a lot of medications, or if you're not getting reasonable relief from the treatments that your primary care physicians prescribe, then seek out a pain specialist."