The researchers found problems in the inner ear and in certain brain function measures that affect hearing. The study's lead researcher, Doctor Robert Frisina of the University of Rochester Medical Center, has urged women considering such therapy to have their hearing checked beforehand and, if they start, every six months thereafter.
The researchers report, "Sensory declines in elderly women, in this case exacerbated by progestin, can significantly interfere with communication abilities, including speech and hearing, professional and economic productivity, family relations, and quality of life."
Dr Robert D Frisina and colleagues used a "rigorous battery of classical and state-of-the art hearing tests assessing both the peripheral (ear) and central (brain) auditory systems," to compare the effects of estrogen alone, estrogen plus progestin, and no HRT (control) on 124 postmenopausal women of ages 60 to 86 years.
Of the 124 subjects, 30 were treated with estrogen alone, 32 with estrogen plus progestin, and 62 served as controls. HRT use among them ranged from 5 to 35 years.
They found that those who were taking progestin as part of their therapy seemed to have a harder time understanding speech than women who were not taking hormones or who were using estrogen only.
The findings of the study appear in tomorrow's issue of Proceedings of the National Academy of Sciences.
The researchers note that the results do not confirm the hypothesis that estrogen alone protects the auditory system, because since none of the tests showed significantly different results between the estrogen and the control groups.
At the end of their study the team recommends that better sensory testing be performed during drug development, especially for drugs intended for use by older individuals.