By the year 2050, an estimated 100 million people or nearly one in 85 individuals worldwide will be affected by dementia. In a new study, hearing loss may be associated with increased risk of dementia and the development of Alzheimer's. In addition, risk increases as hearing loss becomes more severe.
According to MediLexicon.com, dementia is the loss, usually progressive, of cognitive and intellectual functions, without impairment of perception or consciousness; caused by a variety of disorders, (structural or degenerative) but most commonly associated with structural brain disease. Dementia is characterized by disorientation, impaired memory, judgment, and intellect, and a shallow labile affect.
Alzheimer's is the most common form of dementia, a general term for memory loss and other intellectual abilities serious enough to interfere with daily life. Alzheimer's disease accounts for 50 to 70 percent of dementia cases.
The study's authors explain:
"A number of mechanisms may be theoretically implicated in the observed association between hearing loss and incident dementia. Hearing loss may be casually related to dementia, possibly through exhaustion of cognitive reserve, social isolation, environmental differentiation [elimination of sensory nerve fibers] or a combination of these pathways."
However it is important to note that dementia may be over diagnosed in individuals with hearing loss, or those with cognitive impairment may be over diagnosed with hearing loss. The two conditions may share an underlying neuropathologic process.
The study continues:
"If confirmed in other independent cohorts, the findings of our study could have substantial implications for individuals and public health. Hearing loss in older adults may be preventable and can be practically addressed with current technology (e.g., digital hearing aids and cochlear implants) and with other rehabilitative interventions focusing on optimizing social and environmental conditions for hearing. With the increasing number of people with hearing loss, research into the mechanistic pathways linking hearing loss with dementia and the potential of rehabilitative strategies to moderate this association are critically needed."
Of the participants, 125 had mild hearing loss (25 to 40 decibels), 53 had moderate hearing loss (41 to 70 decibels) and six had severe hearing loss (more than 70 decibels). During a median (midpoint) follow-up of 11.9 years, 58 individuals were diagnosed with dementia, including 37 who had Alzheimer's disease.
The risk of dementia was increased among those with hearing loss of greater than 25 decibels, with further increases in risk observed among those with moderate or severe hearing loss as compared with mild hearing loss. For participants age 60 and older, more than one-third of the risk of dementia was associated with hearing loss.
The study concludes:
"Unfortunately, there are no known interventions that currently have such effectiveness. Epidemiologic approaches have focused on the identification of putative risk factors that could be targeted for prevention based on the assumption that dementia is easier to prevent than to reverse. Candidate factors include low involvement in leisure activities and social interactions, sedentary state, diabetes mellitus and hypertension."
The risk of developing Alzheimer's disease specifically also increased with hearing loss, such that for every 10 decibels of hearing loss, the extra risk increased by 20 percent. There was no association between self-reported use of hearing aids and a reduction in dementia or Alzheimer's disease risk.
Written by Sy Kraft, B.A.