While earlier observational studies suggested that postmenopausal hormone treatment may improve cognitive functioning in women, studies from the Women’s Health Initiative have shown that estrogen replacement therapy started in postmenopausal women (65 years or older) did not enhance cognitive functioning nor did it decrease the risk of dementia.

In order to assess the effect of estrogen on cognitive functioning, researchers from the Mayo Clinic studied a group of women who had undergone either unilateral or bilateral oophorectomy. In this study, researchers compared 1489 women who had undergone the removal of one or both ovaries (for a non-cancer indication) with 1472 age-matched women who had not undergone oophorectomy. Women were followed for a median of 27 years and were interviewed about their cognitive functioning.

Women who had one or both ovaries removed before menopause were almost twice as likely to develop cognitive problems or dementia as compared to women who did not have this surgery. Furthermore, women who were younger at the time of oophorectomy were more likely to develop dementia than women who were older when their ovaries were removed. In contrast, women who had their ovaries removed before the age of 49 but received estrogen replacement therapy (at least until the age of 50) were not more likely to experience cognitive problems.

This study suggests that estrogen, while it may not enhance cognitive function in postmenopausal women, may have a protective effect on the brains of younger women and that premature estrogen deficiency – as occurs after the removal of the ovaries prior to the onset of menopause — may increase a woman’s risk of developing cognitive problems or dementia at a later age.

Ruta Nonacs, MD PhD

Rocca WA et al. Increased risk of cognitive impairment or dementia in women who underwent oophorectomy before menopause. Neurology 2007; 69:1074.