The public health impact of hearing loss and cognitive decline on an aging population has been the focus of numerous studies. A July, 2017 Lancet report, for example, suggested hearing loss is one of the strongest modifiable risk factors associated with dementia. Given the high prevalence of hearing impairment in the elderly, and its modifiable nature, hearing aid use to delay or slow down the effects of cognitive decline is a hot topic.
Researchers generally believe there are two theories underpinning the relationship between hearing sensitivity and cognitive ability. The first theory, referred to as the common cause hypothesis, theorizes that hearing loss and cognitive decline share common age-related factors, such as degeneration of tissues within the central nervous system — both cognition and hearing decline at the same rate because the entire system is afflicted in a similar manner. The second theory, commonly known as the cascade hypothesis, posits that prolonged loss of hearing leads to insufficient brain stimulation, leading to cognitive decline as people age.
A study, published in April in the Journal of the American Geriatric Society, sheds light on the relationship between these two common conditions associated with aging, along with the mitigating effects of amplification.
Asri Maharani, Piers Dawes and colleagues at the University of Manchester, in affiliation with the SENSE-Cog WP1 group, examined data drawn from the Hearing and Retirement Study (HRS), which is sponsored by the National Institute of Aging and archived at the University of Michigan. Maharani at al evaluated data collected every two years from adults over the age of 50 between 1996 and 2014. Maharani and colleagues focused on episodic memory performance. Episodic memory was chosen because it is believed to be more sensitive to age than other cognitive variables and has a strong association with dementia.
In the test for episodic memory used in the HRS, interviewers asked participants to immediately repeat simple nouns that were read to them. The total number of words repeated by the participants was scored and this variable was tracked every two years for 18 years. The HRS researchers tracked self-reported hearing aid use by simply asking the participant during the biennial data collection process. The frequency of hearing aid use or quality of the fitting was not tracked by the HRS investigators. The average age of first-time hearing aid use among the group studied was 62 years old.
Hearing Aids Mitigate Trajectory of Cognitive Slowdown
Results for 2,040 self-reported hearing aid users over this 18-year period show the rate of decline on the episodic memory score was slower for self-reported hearing aid users. Episodic memory did decline with age, but the rate of cognitive decline was slower after participants began using hearing aids. These conclusions were made by Maharani and colleagues after adjusting for variables such as overall health, socioeconomic status and other demographic characteristics.
The slower rate of cognitive decline in participants with hearing loss that began using hearing aids supports the cascade hypothesis. As the researchers state in their conclusion, hearing aids may provide individuals with improved auditory input that may delay cognitive decline “by preventing the adverse effects of auditory deprivation or facilitating lower levels of depression symptoms, greater social engagement and higher self-efficacy, which protect cognitive function.”
This study provides further evidence that access to hearing health care has the potential to delay or slow down cognitive decline in older adults with hearing loss. Similar to other studies examining the relationship between hearing loss and cognitive decline, however, the results need to be interpreted with some caution: these studies rely on complex statistical analysis across large pools of patient data to determine the probability of having both conditions. In the clinic, every individual has a unique set of characteristics that make the findings of a large-scale study without the use of a randomized control group difficult to apply. That said, there are some findings from this study that can be generalized across older patient populations, which can be used in the education process.
Educational materials, patient brochures and all other types of communication with the following message are supported by the clinical evidence:
- Hearing aids do not prevent cognitive decline, but there is mounting evidence suggesting hearing aids slow it down.
- Hearing aid users have a greater tendency to be socially engaged, less depressed and more self-confident in their ability to communicate effectively in everyday listening situations, compared to older adults who choose not to use hearing aids. Staying socially engaged and physically active – tasks accomplished in part by using hearing aids – may lessen the effects of dementia.
- Professionally fitted hearing aids as well as other high quality amplification devices need to be recommended to individuals at earlier stages of their hearing loss.
Fuel Medical members can utilize these messages in patient communications to raise awareness within their community of the negative consequences associated with late stage hearing loss identification and encourage adults to seek treatment sooner, if a hearing loss has been identified.
Source: Maharani, A., Dawes, P. et al (2018) Longitudinal relationship between hearing aid use and cognitive function in older Americans. Journal of the American Geriatrics Society. Published online April 26.