Oestrogen gives women's memories a real boost
WOMEN deprived of oestrogen suffer from memory lapses that vanish when the hormone is replaced, a Canadian expert has found. Her findings are a convincing demonstration that oestrogen has a beneficial effect on cognitive circuits in the female brain.
Previous studies have suggested that mental ability is linked to oestrogen exposure in the womb (New Scientist, 31 July, p 15). There is also some evidence that hormone replacement therapy (HRT) protects the brains of postmenopausal women against degenerative diseases such as Alzheimer's. But little is known about how the hormone shapes the intellect of reproductively active women.
Attempts to monitor changes in cognitive performance throughout the menstrual cycle have proved inconclusive, says Barbara Sherwin of McGill University in Montreal, possibly because oestrogen levels only fluctuate slightly and never fall below a certain threshold. Now Sherwin and her colleagues have followed a group of 100 women in their mid-forties, each of whom suffered a sudden drop in circulating levels of oestrogen after their ovaries and uterus had to be surgically removed.
Sherwin divided the women into two groups, one of which received HRT after the operation, the other a placebo. The women were shown pairs of unrelated words and subsequently had to recall the second of each pair when cued by the first word. The women on HRT scored just as well as they had before their operation. But the placebo group performed significantly worse, Sherwin told a meeting in London last week on the cognitive effects of oestrogen, organised by the Novartis Foundation and the Wellcome Trust.
The women in the placebo group also noticed changes in their own behaviour. They complained of not being able to remember things and of having to make lists, which they had never needed to do in the past. "They weren't demented, they weren't losing their jobs or unable to function," says Sherwin. "Nonetheless it was a documentable decrease."
Sherwin has also looked at a group of women in their early thirties who had uterine tumours. Because the growth of these tumours is promoted by oestrogen, the women had been treated with a drug that suppressed production of the hormone. After treatment, half the women were given HRT. The other half acted as controls.
Again, loss of oestrogen lowered the women's memory scores. Two months after treatment with the oestrogen suppressor had stopped, women given HRT were back to normal. But the controls, whose oestrogen levels still hadn't returned to normal, showed the same memory deficit.
Bruce McEwen, a neuroendocrinologist at Rockefeller University in New York, says Sherwin's work is clearcut. "There are reversible cognitive deficits that are not of enormous magnitude, but enough to bother high-functioning women so that they should report them to their gynaecologist," he says.
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