Do the brains of men and women age differently?

Some studies have suggested that the brains of men and women age differently, but there's little consensus as to how they differ. Some researchers found that men's brains were more vulnerable to the effects of age than women. Other studies showed the reverse to be true, and still others found that men and women differ in the types of cognitive decline they experience.

Additionally, some researchers have suggested that diseases such as hypertension, heart disease, and diabetes may be a more critical factor in brain aging than gender.

It has also been suggested that for women, estrogen may have a protective effect on the brain. This has been found to be true in studies with animals. When female rodents were deprived of estrogen, they lost critical connections between neurons in their brains. Scientists theorized that hormone replacement therapy for postmenopausal women, which replaces estrogen, might slow down age-related cognitive decline.

A recent study from the Women's Health Initiative, however, casts doubt on that theory. The study, reported in the May 28, 2003, issue of the Journal of the American Medical Association, showed that healthy women taking estrogen and progestin hormone replacement therapy were twice as likely to develop dementia as women taking placebo. Furthermore, the combination hormone therapy did not protect women from developing mild cognitive impairment. However, it may be that only estrogen alone is effective. A study of the possible preventive effects of estrogen-only therapy on healthy women who have had a hysterectomy is still ongoing. A study of rhesus monkeys published in the July 2003 issue of the Journal of Neuroscience lent support to the theory, finding that cyclic estrogen replacement in female monkeys whose ovaries had been removed reversed age-related cognitive decline.