An argument could be made that some other, yet-to-be-determined physiologic factor may serve as a common cause for both hearing loss and dementia. But Dr. Lin believes that the strength of the epidemiologic evidence suggests otherwise. “If we saw a relatively small effect, it would be logical to dismiss the link between hearing and cognition as just being part of some natural aging process or from unaccounted cardiovascular risk factors. But when you see that strong of a link, it’s unlikely that any degree of confounding by other physiologic risk factors could fully argue away that effect,” Dr. Lin said. “Clearly, something else is going on.”
Explore this issue:May 2013
What Interventions Work?
Dr. Lin acknowledged that a key question remains: Can cognitive declines be reduced by hearing aids and other rehabilitative interventions? “Scientifically, we just have no clue,” he said. “It may be that those interventions are too little, too late. However, from a clinical standpoint—based on my own practice experience—these interventions, whether a hearing aid or cochlear implant, do seem to make a difference.”
He cited the example of an older patient with age-related hearing loss whom he typically treats with hearing aids or other assistive devises and ongoing rehabilitative hearing therapy. “Fairly quickly, you can see the difference in the lives of patients who are treated this way,” he said. “All of a sudden, they are able to engage again; they are no longer isolated. These really can be dramatic effects but, of course, this is just base on clinical impression right now.” He did point out, however, that earlier researchers have made a connection between social isolation, cognitive load and cognitive function (Psychol Aging. 2009;24:761-766).
The next step in Dr. Lin’s research is to investigate whether hearing-loss interventions could in fact reduce the risk of cognitive decline and dementia. “We’ve just submitted a grant to carry out this definitive clinical trial,” he said. The trial will randomize half of a group of older patients with hearing loss to treatment and half to watchful waiting. “Assuming that hearing loss treatment could have even a modest effect on helping reduce cognitive decline, this could be a seminal study that will finally give this issue the degree of public health urgency that it truly deserves.”
To increase awareness about hearing loss and its effects on dementia, Dr. Lin recently began working with the Bloomberg School of Public Health to raise funds for a Center on Hearing and Healthy Aging (see “Multidisciplinary Initiative Seeks to Improve Age-Related Hearing Loss Treatment,” below).