A new study published in the February 2011 issue of Archives of Neurology shows that adults with hearing loss have a greater chance of developing dementia, a risk that increases as their deafness worsens.
By Joni Doherty, MD, Ph.D.
A new study published in the February 2011 issue of Archives of Neurology has confirmed what a lot of physicians who take care of patients with hearing loss and dementia have suspected for a while: that adults with hearing loss have a greater chance of developing dementia, a risk that increases as their deafness worsens.
The investigation into the potential association between hearing loss and dementia focused on 639 men and women between the ages of 36 and 90, none of whom had dementia at the start of the study in 1990.The research participants were given cognitive and hearing tests between 1990 and 1994, followed by patient tracking through 2008 (for an average of about 12 years) to monitor for signs of dementia and/or Alzheimer's. A little less than 30 percent of the study participants had some hearing loss at the start of the study, which was funded by the National Institute on Aging.
Overall, 9 percent of the participants went on to develop Alzheimer's disease or another form of dementia. And the study found that the more severe the hearing loss was, the greater the risk of developing dementia. Mild, moderate, and severe hearing loss were associated with a two-fold, three-fold, and five-fold higher risk of later dementia, respectively, in comparison to normal hearing.
"This work suggests that there is a strong predictive association between hearing loss as an adult and the likelihood of developing cognitive decline with aging," said study lead author Dr. Luigi Ferrucci, chief of the U.S. National Institute on Aging's Longitudinal Studies Section, as well as director of the Baltimore Longitudinal Study of Aging. The reasons are not known, however. "The brain might have to reallocate resources to help with hearing at the expense of cognition," says the lead researcher, Frank R. Lin, M.D., an ear surgeon at Johns Hopkins Hospital in Baltimore. That may explain in part why straining to hear conversations over background noise in a loud restaurant can be mentally exhausting for anyone, hard of hearing or not, he adds. In other words, we listen with our ears but hear with our brains. It may simply not be possible to separate audition and cognition.
Or it may be that hearing loss and dementia might share a common, unknown cause. Elderly people who are hard of hearing might also have extra difficulties coping with declining mental function. In addition, the social isolation and loneliness sometimes brought about by hearing impairment could also fuel the dementia.
Lin and his colleagues have begun researching the effect of hearing aids on the risk of dementia. "Whether or not it can help dementia, we don't know yet," he says. "But in the meantime, there's no reason not to take your hearing loss seriously and pursue some type of treatment."