Hearing loss is a common consequence of aging. Almost three-quarters of American adults aged 70 and over have some degree of hearing loss. One unanswered question has been to what extent hearing loss interferes with age-related cognitive decline and influence.
In a new study, researchers at the University of California, San Diego School of Medicine report that hearing loss is associated with accelerated cognitive decline with age, although the impact of mild hearing loss may be mitigated by higher education.
The results are published in the February 12, 2019 issue of the Journal of Gerontology: Series A Medical Sciences.
A team of scientists, led by senior author Linda K. McEvoy, Ph.D., professor in the departments of radiology and family medicine and public health, followed 1,164 participants (mean age 73.5 years, 64 percent of women) in the Rancho Bernardo Longitudinal Study of Healthy Aging up to 24 years. All had undergone hearing and cognitive function assessments between the years 1992 to 1996 and had up to five subsequent cognitive assessments at approximately four-year intervals. None used a hearing aid.
The researchers found that almost half of the participants had mild hearing loss, with 16.8 percent suffering from moderate to severe hearing loss. People with more severe hearing loss performed worse on the initial visit on a pair of commonly used cognitive assessment tests: the Mini-Mental State Exam (MMSE) and the Trail-Making Test, Part B. Hearing loss has been associated with a greater decline in performance on these tests over time, both for people with mild hearing loss and for those with more severe hearing loss.
However, the association of mild hearing loss with the rate of cognitive decline has been altered by education. Mild hearing loss was associated with a more pronounced decline in study participants without a university degree, but not in those with a higher education. Moderate to severe hearing loss was associated with a more pronounced decline in MMSE, regardless of education level.
âWe speculate that higher education can provide sufficient cognitive reserve to counter the effects of mild hearing loss, but not enough to overcome the effects of more severe hearing loss,â McEvoy said.
The degree of social engagement did not affect the association of hearing loss with cognitive decline. âIt was a somewhat unexpected discovery,â said first author Ali Alattar. “Others have postulated that cognitive impairments related to hearing loss may result from social isolation, but in our study, participants with hearing loss were as socially engaged as those without hearing loss.”
The results, the authors said, underscore the need for physicians to be aware that elderly patients with hearing impairments are at greater risk for cognitive decline. They also stressed the importance of preventing hearing loss at all ages, as hearing loss is rarely reversible. An important way to protect hearing, they said, is to minimize exposure to noise as it is the greatest modifiable risk factor for hearing loss.
Co-authors include: Jaclyn Bergstrom, Gail A. Laughlin, Donna Kritz-Silverstein, Erin L. Richard, Emilie T. Reas, Jeffrey P. Harris, and Elizabeth Barrett-Connor, all at UC San Diego.
Funding for this research comes, in part, from the UC San Diego School of Medicine and National Institutes of Health Clinical Research Fellowship (R01-AA021187, R01-AG054067, R01-AG028507, R37-AG007181, R01- DK31801, UL1TR001442).