Although researchers have suggested for years that estrogen is connected to migraines, there haven't been any studies that reveal the exact nature of this connection. Now, a new study has revealed that women with a history of migraines experience rapid drops in estrogen levels in the days prior to menstruation compared to women with no history of migraines. No other connections between migraines and other hormone patterns were found.

In addition, the study suggests that women with a history of migraines experience a faster drop in estrogen levels regardless of whether they experience a migraine during their current menstrual cycle.

"These results suggest that a 'two-hit' process may link estrogen withdrawal to menstrual migraine," said Jelena Pavlovic of the Albert Einstein College of Medicine and lead author of the study. "More rapid estrogen decline may make women vulnerable to common triggers for migraine attacks such as stress, lack of sleep, foods and wine."

During the course of the study, the team examined 114 women with a history of migraines and 223 women with no history of migraines. In particular, they looked at the participants' history, daily headache diaries and hormone data. The average age of the women was 57 years old.

The team measured hormone levels through the analysis of daily urine samples of one monthly cycle, while peak hormone levels, average daily levels and day-to-day rates of decline were obtained during the five-day period following the hormone peak in their cycles.

The results revealed that in the two days following peak estrogen levels in the luteal phase of the menstrual cycle, estrogen levels in women with migraine history declined by 40 percent, compared to just 30 percent for women without a history of migraines.

Furthermore, the rate declined by 34 picrograms per milligram of creatinine (pg/mgCr) in women with a history of migraines compared to 23 pg/mgCr in women without a history of migraines.

"Future studies should focus on the relationship between headaches and daily hormone changes and explore the possible underpinnings of these results," Pavlovic said.

Despite the suggestions of the study, the group of women with no migraine history contained significantly more Chinese and Japanese women than the group of women with a history of migraines, which contained more black and white women. Further studies should conduct similar analyses on groups with a more even proportion of ethnicities, as sex hormone levels can differ by race and ethnicity.

The findings were published in the June 1 issue of the journal Neurology.