Hormone replacement therapy may protect against memory loss and Alzheimer’s disease after the menopause, a study by British scientists has suggested.

Women’s memories worsen significantly when they have a medical procedure that mimics the effect of the menopause, before recovering when hormone flow resumes, research at the Institute of Psychiatry in London has found.

The findings, from a team led by Michael Craig, who is trained as both a psychiatrist and a gynaecologist, offer insights into how menopause changes the female brain, and hint that hormone replacemnt therapy (HRT) could protect it against dementia and cognitive decline.

Research by the same group is also promising to unravel how the female hormone oestrogen affects mood, which could lead to new approaches to treating depression and premenstrual syndrome.

Women have a higher risk of Alzheimer’s disease and other forms of dementia than men, even once their longer average lifespans are taken into account, which is often attributed to the influence of female hormones.

Oestrogen has a neuroprotective effect, preventing the build-up of beta-amyloid plaques that form in the brain cells of Alzheimer’s patients, and the risk of dementia may rise when hormone levels fall after the menopause.

HRT may, therefore, protect against Alzheimer’s, but the 2002 Women’s Health Initiative trial found the reverse, as well as suggesting that the drugs may increase breast cancer and cardiovascular disease.

More recent analysis has indicated that while the link to breast cancer is real, the negative effects on heart disease and dementia apply only when HRT is taken by women in their 60s.

“There is growing evidence to support a theory that there is a critical window when you hit the menopause,” Dr Craig told The Times. “If you have HRT at the time of menopause, it may confer significant protection, but if you don’t start it until ten years afterwards the damage may be done.”

To investigate how menopause affects the brain, Dr Craig’s team studied 30 young, premenopausal women who were having surgery at two London hospitals for fibroids – benign womb growths. These patients are generally given a gonadotrophin-releasing hormone agonist, a drug that shuts down the ovaries and induces a temporary menopause. This shrinks the fibroids before surgery.

This effect allowed Dr Craig to examine what happens to the brain when its oestrogen supply is shut off and then reactivated, much as happens when the menopause is followed by a course of HRT.

All the women were given a memory test in which they had to identify words they had seen before. Their average accuracy was about 75 per cent before treatment. This fell to 65 per cent while their ovaries were not working, but then recovered to 75 per cent when oestrogen was restored.

“It’s further evidence that the brain systems that are involved in dementia are adversely affected by loss of ovarian function,” Dr Craig said.

“The findings are consistent with what you would expect to see if oestrogen is protecting against the sort of neurological damage that occurs in Alzheimer’s dementia.”

The researchers also found different patterns of brain activity during induced menopause, in the prefrontal cortex that is involved in higher cognitive functions. While the findings do not prove that HRT protects against dementia, they do suggest that it is likely to, Dr Craig said.

Pros and cons of therapy

— The Women’s Health Initiative involved 16,000 American women who took HRT or a placebo. The HRT group was found to have a higher risk of breast cancer, heart disease, strokes and dementia, and the trial was stopped in 2002

— While the breast cancer link is considered robust, there is now evidence that HRT may protect against heart disease and dementia if taken early Source: Times database

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