That’s the opposite of what scientists had expected to find. For years, they had hypothesized that supplemental hormones might be a way for women to fend off hearing loss or further improve their hearing as they aged. Robert D. Frisina, a neuroscientist at the University of Rochester Medical Center and researcher at the National Technical Institute for the Deaf, located at the Rochester Institute of Technology (RIT/NTID), and his colleagues wanted to test the theory by checking to see if women taking estrogen as part of hormone therapy had better hearing than women not taking hormone therapy.
With funding from the National Institutes of Health, researchers at RIT/NTID and the University of Rochester medical school conducted a pilot study, published in 2004, comparing the hearing of 64 women between the ages of 60 and 86. Half of the women were taking hormones, either a combination of estrogen and progestin (the type of hormones that symptomatic women who have not had a hysterectomy typically take), or estrogen alone (the type of hormones that symptomatic women who have had a hysterectomy generally take). A control group took no hormones. The composition of each group was carefully matched.
But when the results came in, there was little or no improvement detected in the group taking estrogen only, and the women taking combined hormone therapy (estrogen and progesterone) scored significantly worse on simple hearing tests than those getting a placebo. Specifically, the group taking combined hormone therapy scored 10 to 30 percent worse, depending on the type of hearing test used. They did particularly badly on hearing tests that measured their ability to make out what someone was saying to them in a noisy room, the kind of situation you might encounter at a bustling cocktail party or restaurant.
Because the pilots had so few participants, a larger study was needed to confirm the results. So the same researchers recruited 124 healthy women (ages 60 to 86) who had been taking hormones for five to 35 years to do the same retrospective single-blind study on a larger scale and monitored their hearing with more-sophisticated tests. The results were published online last week in the Proceedings of the National Academy of Sciences, and they echo the earlier findings. Once again, the group taking combined hormones had a documented hearing loss of 10 to 30 percent compared to the women who hadn’t taken any hormones. That’s a loss equivalent to aging another five to 10 years. In fact, those taking the combined hormones did worse on every type of hearing test they got—from the standard “pure tone” test (where you raise your hand to signal the tester that you’ve heard something) to more sophisticated tests that measure sound echoing out of the ear.
Since the women taking estrogen only did not experience any hearing loss, researchers have concluded that the likely culprit is progesterone. That fits with some anecdotal evidence from women prescribed supplemental progesterone to help maintain a pregnancy; they often complain that their hearing gets noticeably worse while they’re on the medication. A few studies have also shown that young women don’t do as well on auditory testing during the portion of their menstrual cycles when progesterone is highest.
What happens now? More research is needed, said Frisina. “Not much is known about progesterone,” he said. “One of the questions people ask is, “Is this problem reversible?’ We don’t know. We also don’t know if hearing is affected in younger women taking combined hormones for a shorter time.” Frisina said researchers are also interested in studying whether birth-control pills (which include progesterone) have a negative effect on younger women’s hearing, and whether all types of progestogens (natural and synthetic) cause similar damage.
In the meantime, Frisina says, along with increased risk of stroke, blood clots, heart disease, breast cancer and dementia, hearing loss should be one more thing women consider when deciding whether to take combined hormone therapy to relieve hot flashes, night sweats and vaginal dryness. That’s especially true for women who already have hearing problems, he said. And he advises those who decide to use combined hormones to get their hearing checked every six months.
This research also raises the intriguing notion that menopause—when the body’s natural production of progesterone comes to a complete halt—might give women a kind of hedge against age-related hearing problems. More research is needed to answer that question as well.
