The relationship between cognitive ability and hearing aid use in older adults has drawn considerable interest over the past several years for obvious reasons: Many nations around the world are coping with a growing aging population, along with many of the consequences that accompany it. Hearing loss and cognitive decline being two of the common ill-effects associated with aging.
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. A subject that Hearing News Watch has covered previously here and here.
Researchers generally believe there are two theories underpinning the relationship between hearing acuity and cognitive ability. The first, 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, commonly known as the cascade hypothesis, posits that prolonged loss of hearing leads to insufficient brain stimulation, leading to cognitive decline as people age.
Recent Study Examines Connection Between Hearing Aid Use and Cognition
A study, published this month 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 it has a strong association with dementia.
In the test for episodic memory used in the HRS, interviewers asked participants to immediately repeat simple nouns they had 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 hearing aid use by self-report, 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 2040 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 enable individuals improved auditory input which 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 healthcare has the potential to delay or slow down cognitive decline in older adults with hearing loss.
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
*featured image courtesy flckr