Researchers at Rush University Medical Center (Chicago, IL, USA) conducted a retrospective, case-control study over a two-year period (2008-2010) of a group of 60 women (aged 31-80), with both unruptured and ruptured aneurysms; 65% of the cases were unruptured and 35% were cases where women had ruptured aneurysms. The researchers compared a variety of factors in the case group to that of a control group including 4,682 random females, to determine if a link existed between lower estrogen levels and aneurysm incidence. Both groups were screened with questions related to their gynecologic history and the use of estrogen modifying medications. Some of the variables included menstrual onset, the woman's age at the time of birth of her first child, use and duration of oral contraceptives and hormone replacement therapy, and age of the start of menopause.

The researchers found strong similarities existed across multiple screening factors between the groups; however, when it concerned use of estrogen modifying agents such as oral contraceptives and HRT, there were major differences between the two groups. The rate of oral contraceptive usage in the case group was 60% compared to 77.6% for the control group. Also, the rate of HRT usage was 23.7% for the case group and 44.8% for the control group. When comparing the median duration of oral contraceptive use, results showed that the average duration was 2.6 years for the case group and 5.2 years for the control group. The researchers suggest that the study provides further evidence that estrogen stabilization may play a protective role in women who are at risk of aneurysms. The study findings were presented at the Society of Neurointerventional Surgery (SNIS) annual meeting, held during July 2010 in Carlsbad (CA, USA).

"These differences in the usage of estrogen modifying agents qualify as statistically significant and indicate that women with brain aneurysms use oral contraceptives and hormone replacement therapy less frequently than the general population,” said lead author neurointerventionalist Michael Chen, M.D. "It is reasonable to conclude that the data results support our hypothesis that drops in estrogen that occur in menstruation and particularly at menopause may explain why cerebral aneurysms are more frequently found in women, particularly at menopause.”

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Rush University Medical Center