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18:00 24 February 04
NewScientist.com news service
Post-menopausal women who receive hormone replacement therapy may risk diminished hearing, suggest the results of a new study.
Tests on 64 women over the age of 60 – half of whom were on HRT – showed that those taking HRT had 10 to 30 per cent worse hearing than those not taking HRT.
But the HRT group did not just perform badly on tests that measure how well the ear actually detects a sound – tests on how well the brain processes that information showed that those on HRT had their processing ability reduced by an average of 30 per cent.
“This would be most noticeable in situations where there’s a lot of background noise and information needs to be filtered and prioritized in a way that can be understood. The most obvious situation is a party where a lot of people are talking and you’re trying to listen to one particular person,” explains Robert Frisina at the University of Rochester Medical Center, who led the small pilot study.
“This type of hearing loss occurs naturally as a part of ageing, but it appears as if the ageing process, when it comes to hearing, was accelerated in these women,” he told New Scientist.
It is not understood why HRT might have this effect on hearing, indeed, Frisina had expected the hormones to enhance hearing ability. “These results are very surprising. We thought hormones would help women hear better, because of the presence of estrogen receptors in the ear.”
Fluctuations in estrogen and progesterone cause ionic imbalances in the body, particularly with regard to sodium and potassium levels – a noticeable symptom of this is the water retention that occurs during the menstrual cycle. Frisina speculates that this imbalance may affect hearing.
“The ear is particularly sensitive to ionic imbalance and other studies have shown that hearing ability changes throughout a woman’s menstrual cycle,” he says.
Although the current study is small, Frisina urges women to be cautious of HRT.
“Our findings raise concerns. It’s important to alert women that there could be another significant side-effect of HRT. A much larger study needs to be done,” he says. And, because the inner ear is affected, Frisina cautions that balance problems – a leading cause of injury among the elderly – may also be a concern for women taking HRT.
But John Stevenson, from the British Menopause Society, is skeptical, saying that the study is too small to be conclusive. “I would be very cautious in interpreting the results before a proper prospective large-scale study is carried out.
“If there really was a 30 per cent difference in hearing ability in women who take HRT, then I think we would have been aware of it clinically – patients would have complained about it and clinicians would have reported it,” he told New Scientist.
Previous research has linked HRT to increased risks of breast cancer, heart attacks, and stroke. This latest study was presented at the annual meeting of the Association for Research in Otolaryngology in Daytona, Florida on Tuesday.