By the time Americans reach their 70s, two-thirds experience hearing loss. Indeed, age-related hearing loss is the third most common geriatric health condition and one that Justin S. Golub, MD, MS, an otologist/
Dr. Justin Golub
According to recent research, including studies by Dr. Golub’s team at Columbia, this troublesome and often inevitable condition in later life may also increase the risk of cognitive problems and dementia. “There is a growing interest in age-related hearing loss as a public health issue, particularly as several major studies have shown that older adults with hearing loss are more likely to develop Alzheimer’s disease and related dementias compared to those with normal hearing,” says Dr. Golub. “While it is not known at this time whether hearing loss causes dementia, theoretical models propose a causal link. For example, hearing loss can result in social isolation or difficulty processing the higher content of speech. Over time, this might reduce cognitive stimulation and render the individual more prone to dementia.”
Among Dr. Golub’s research endeavors are investigations into the associations and effects of age-related hearing loss on the brain, including whether worsening hearing is associated with higher β-amyloid burden; neuropsychiatric complications of hearing loss; and whether age-related hearing loss may increase the risk of dementia and depression.
Does Early Hearing Loss Lead to Dementia?
Although there is no conclusive evidence linking hearing loss to dementia, studies have raised this possibility and several have also linked this condition to Alzheimer’s disease with one model suggesting that it may lead to dementia through changes in brain structure. To examine this further, Dr. Golub and his Columbia colleagues led a cross-sectional analysis of a prospective cohort study to examine potential mechanistic associations between hearing loss and dementia using brain imaging biomarkers of dementia. The availability of amyloid positron emission tomography (PET) has made it possible to non-invasively measure the accumulation of brain β-amyloid plaques.
To their knowledge, the Columbia researchers note that this is the first study to show an association between hearing loss and brain β-amyloid, the characteristic pathologic feature of Alzheimer’s disease.
In their study, the researchers analyzed the association between audiometric hearing loss – measured by either pure-tone average or word recognition score in the better ear – and the extent of β-amyloid plaque of Alzheimer’s disease according to PET scans. The cross-sectional study focused on participants in the Northern Manhattan Study of Metabolism and Mind, a community-based prospective study based at Columbia. Of the 460 subjects in the Northern Manhattan Study, 118 had been given a hearing test and of those, 98 individuals had brain β-amyloid measured by PET scan.
The study’s findings, which were published in the March 2021 issue of The Laryngoscope, demonstrated that worsening hearing was associated with higher β-amyloid burden, a pathologic hallmark of Alzheimer’s disease. According to the authors, “Audiometric hearing loss was independently associated with brain β-amyloid measured on PET scan. The association was robust to the adjustment of multiple confounders, including demographics, education, cardiovascular disease, and hearing aid use.”
The authors added that future longitudinal and randomized controlled studies should examine whether hearing loss is causally related to Alzheimer’s and related dementias.
Exploring Links to Neuropsychiatric Concerns
The neurocognitive profile of individuals with age-related hearing loss is not well understood.
To this end, Dr. Golub collaborated with colleagues in the New York State Psychiatric Institute in a study to categorize the neuropsychological profile of hearing loss. The study cohort drew on the National Alzheimer’s Coordinating Center’s database and included individuals with normal cognition and those with mild cognitive impairment and dementia.
The researchers’ analysis of 8,529 older adults found important relationships between hearing loss, neurocognitive performance, and incident dementia. At baseline, they discovered that hearing loss untreated was associated with decreased cognitive ability on measures of executive function and language fluency compared to those without hearing loss. Hearing aids appeared to help minimize decline in neurocognitive performance at baseline. However, more than 45 percent of the individuals with untreated hearing loss and nearly 50 percent with treated hearing loss demonstrated executive dysfunction during follow-up. Specifically, lower performance across all cognitive domains – global cognition, attention, processing speed, executive function, episodic memory, and language fluency – predicted an increased risk for dementia over an average follow-up period of 5.6 years.
The Columbia researchers emphasized that future studies using cognitive batteries designed for hearing impaired populations are needed to further assess the cognitive profile of age-related hearing loss. This research may then identify targets for early interventions, such as effective hearing remediation, to alter the trajectory of a phenotype at high risk for dementia. The results of the study appeared in the 2021 issue of the Journal of Alzheimer’s Disease.
