Hearing loss has been associated with cognitive decline in older adults [1]. However, because this association is derived from observational studies, whether hearing loss plays a causal role in cognitive decline has been unclear. A recent clinical trial set out to determine whether correcting hearing loss through the use of hearing aids could meaningfully reduce the risk for cognitive decline in older adults.
The ACHIEVE trial included 973 cognitively normal adults with untreated hearing loss between the ages of 70 to 84 years old [2]. Half of the participants received hearing aids along with repeated counseling sessions with an audiologist to learn how to properly use and adjust the devices to meet their needs. The trial included a group of individuals who could be considered healthy agers, with generally healthy lifestyles and few dementia risk factors. Across the board, these individuals remained cognitively healthy throughout the duration of the study. In contrast, the trial also included another group of individuals who were at higher risk for cognitive decline based on cardiovascular, metabolic and socioeconomic risk factors. The study found that the hearing aid intervention resulted in a 48% slowing of global cognitive decline in the high-risk individuals, over the course of the three-year study. The effects were most pronounced in language-related cognitive function.
The SENSE-Cog study, which included 252 participants with dementia, found that correcting vision and hearing impairment through the use of glasses and hearing aids could improve quality of life measures for dementia patients in a clinically meaningful manner [3].
These studies suggest that hearing aids may offer benefits for individuals at risk for dementia as well as those living with dementia. However, the benefits are not derived from the hearing aid alone, but rather by the combination of the hearing aid with sustained support from an audiologist or sensory therapist. In the SENSE-Cog study, the hearing aid-related benefits were not maintained once the sensory support ended. Hearing aids need to be carefully calibrated to each individual, and the settings may need to be changed when used in different contexts. The hearing aids can also be paired with devices, such as a smart phone, to allow for more control over the sound quality.
Unfortunately, most private and government insurance plans in the United States, such as Medicare, are currently not required to cover hearing aids or audiologist visits [4]. Therefore, the out-of-pocket costs for hearing aids, typically several thousand dollars for the device alone, may be out of reach for many older adults with hearing loss. Over the counter hearing aids have recently been approved by the FDA, and may be a less expensive option [5]. However, it is important to also budget for supportive services to ensure that the devices can be customized to your unique hearing needs. The protective effects seen in the clinical trials were dependent on consistent use, so it is critical that the devices properly improve hearing capacity.
Several leading ideas have been put forth to try to explain the connection between hearing loss and cognition [6]. These include biological factors, in which the loss of auditory input negatively impacts brain function, as well as psychosocial factors, such as social isolation and depression. One study including over 400,000 participants sought to determine the contribution of these different mechanisms to how hearing aids benefit cognition [7]. Overall, biological factors appear to be the major contributors, while approximately 10% of the relationship between hearing aid use and reduced risk for cognitive decline appears to be mediated by the reduction in psychosocial risk factors. This suggests that other interventions targeting psychosocial risk factors may also provide cognitive benefit for older adults with hearing loss.
While these studies provide encouraging evidence that properly calibrated hearing aids can help mitigate the risk for cognitive decline in individuals with hearing loss, the best course of action is to try to prevent hearing loss in the first place. Protect your hearing at all stages of life by avoiding exposure to loud sounds and wearing protective ear plugs or muffs in loud environments.
Betsy Mills, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Mills came to the ADDF from the University of Michigan, where she served as the grant writing manager for a clinical laboratory specializing in neuroautoimmune diseases. She also completed a Postdoctoral fellowship at the University of Michigan, where she worked to uncover genes that could promote retina regeneration. She earned her doctorate in neuroscience at Johns Hopkins University School of Medicine, where she studied the role of glial cells in the optic nerve, and their contribution to neurodegeneration in glaucoma. She obtained her bachelor's degree in biology from the College of the Holy Cross. Dr. Mills has a strong passion for community outreach, and has served as program presenter with the Michigan Great Lakes Chapter of the Alzheimer's Association to promote dementia awareness.
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