Estrogen Could Prevent Brain Aneurysms in Post-Menopausal Women

Author:  Suvash Shrestha
Institution:  Kathmandu Medical College, Nepal
Date:  October 2010

A recent study showed that oral contraceptives (OC) and hormone replacement therapy (HRT) could protect against the formation of brain aneurysms and rupture of cerebral blood vessels in postmenopausal women. Researchers from Rush University presented their findings at the 7th annual meeting of the Society of Neurointerventional Surgery in California.

Michael Chen, the lead author, stated that two previous extensive trials prompted them to conduct the study. Those two trials found that 70% of cerebral aneurysms, widening of blood vessels in the brain, occurred (on average) in 52-year-old post-menopausal women. Since this is the age when women experience a significant drop in estrogen level, Chen and his team hypothesized that estrogen plays an important role in the prevention of aneurysms. In fact, previous studies have shown that estrogen helps to maintain normal tissue collagen, thus providing tensile strength to the tissue. In estrogen-deficient conditions, the walls of the blood vessels become weak and, consequently, are more likely to widen as a result.

"By understanding the potential link between low levels of estrogen and aneurysms, we can focus our areas of study with the hope of providing women who are at risk for brain aneurysms with preventative therapies," said Chen.

In controlled case studies conducted between 2008 and 2010, Chen and his colleagues examined 60 women with cerebral aneurysms. Thirty-five percent of these patients were found to have ruptured vessels. The researchers then randomly selected approximately 4,700 women from the general population to make up the control group. Chen and his colleagues compared different variables between the two groups, including age at menstrual onset, age at the time of her first child, use and duration of OC and HRT, and menopausal age.

The two groups were similar in many factors. Their median age was 53 years. The average body mass index (the ratio of body weight to height) was 27.1 for the case group and 25.2 for the control group. Ten percent of the experimental group and eleven percent of the controls had their first pregnancy after they were thirty years old. The average age of menstrual onset was thirteen for both groups.

However, the case studies showed that the two groups were significantly different in terms of their usage of estrogen-modifying agents like OC and HRT. Only about 25% percent of the case group, compared to 45% percent of the controls, used HRT. Likewise, only 60% of case group used OC in contrast to the 78% of their control counterpart. In addition, those in the control group used OC for nearly twice as long as those with cerebral aneurysms.

"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 Chen. "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."