Link between hearing and cognition begins earlier than once thought

Summary: Lower levels of cognitive function were observed in people whose hearing was slightly impaired by aging but was still considered to be normal. The findings suggest cognitive impairment starts as soon as hearing becomes imperfect.

Source: Columbia University

Research has shown that adults with age-related hearing loss have higher rates of cognitive decline. Now, a study from researchers at Columbia University Vagelos College of Physicians and Surgeons has found that even the earliest stage of hearing loss–when hearing is still considered normal–is linked to cognitive decline.

The study was published online today in JAMA Otolaryngology-Head and Neck Surgery.

Link Between Hearing Loss and Cognitive Impairment

Age-related hearing loss is one of the most common health disorders of aging, affecting two-thirds of those over age 70. However, few adults are tested for hearing loss, and even fewer are treated. Only 14% of adults with hearing loss in the United States wear hearing aids, the standard treatment.

Because studies show people with age-related hearing loss are more likely to have impaired cognition, it is thought that hearing loss may trigger cognitive decline.

But these studies have only examined people diagnosed with hearing loss, which is defined as the inability to hear sounds under 25 decibels (dB).

“Physicians in this field have used 25 dB–about the loudness of a whisper–to define the border between normal hearing and mild hearing loss in adults, but this level is arbitrary,” says Justin S. Golub, MD, MS, assistant professor of otolaryngology-head and neck surgery at Columbia University Vagelos College of Physicians and Surgeons and a hearing specialist at Columbia University Irving Medical Center and NewYork-Presbyterian Hospital.

“It has been assumed that cognitive impairment wouldn’t begin until people passed this threshold. But no one actually looked at whether this was true.”

Any Hearing Loss May Be Cause for Concern

The researchers looked at data from 6,451 adults (average age 59) who were enrolled in two ethnically diverse epidemiologic studies. Participants underwent hearing and cognitive testing as part of the studies.

Golub and his colleagues found that for every 10 dB decrease in hearing, there was a significant decrease in cognitive ability, a pattern seen across the entire spectrum of hearing.

Surprisingly, the largest decrease in cognitive ability occurred in those whose hearing was just starting to become impaired, just 10 dB off the perfect mark.

“Most people with hearing loss believe they can go about their lives just fine without treatment, and maybe some can,” says Golub. “But hearing loss is not benign. It has been linked to social isolation, depression, cognitive decline, and dementia. Hearing loss should be treated. This study suggests the earlier, the better.”

Can Hearing Aids Prevent Cognitive Loss?

The current study did not address whether hearing loss causes cognitive impairment. It is possible that early declines in both hearing and cognitive performance are related to common aging-related processes, the researchers noted.

This shows a person talking and an ear
Surprisingly, the largest decrease in cognitive ability occurred in those whose hearing was just starting to become impaired, just 10 dB off the perfect mark. The image is in the public domain.

“But it’s also possible that people who don’t hear well tend to socialize less and, as a result, they have fewer stimulating conversations. Over many years, this could have a negative impact on cognition,” says Golub. “If that’s the case, preventing or treating hearing loss could reduce dementia incidence–by more than 9%, according to a recent analysis published in The Lancet.”

A new study, funded by the National Institutes of Health, is now testing the possibility that hearing aids can slow cognitive decline in older people with age-related hearing loss.

More studies are needed before recommending changes in hearing loss categories. “One possibility is to formally introduce a new category, such as borderline hearing loss, ranging from 16 to 25 dB of hearing ability,” says Golub.

Funding: The research was supported by grants from the National Institutes of Health (K23AG057832, L30AG060513, and K24AG045334).

Dr. Golub reports receiving travel expenses for industry-sponsored meetings from Cochlear, Advanced Bionics, and Oticon Medical; consulting fees from Oticon Medical, and Auditory Insight, Optinose, and Decibel Therapeutics; honoraria from Abbott; and departmental educational grants from 3NT, Storz, Stryker, Acclarent, and Decibel Therapeutics.

About this neuroscience research article

Source:
Columbia University
Media Contacts:
Helen Garey – Columbia University
Image Source:
The image is in the public domain.

Original Research: Closed access
“Association of Subclinical Hearing Loss With Cognitive Performance”. Justin S. Golub, MD, MS; Adam M. Brickman, PhD; Adam J. Ciarleglio, PhD; et al.
JAMA Otolaryngology – Head & Neck Surgery doi:10.1001/jamaoto.2019.3375.

Abstract

Association of Subclinical Hearing Loss With Cognitive Performance

Importance
Age-related hearing loss (HL) is a common and treatable condition that has been associated with cognitive impairment. The level of hearing at which this association begins has not been studied to date.

Objective
To investigate whether the association between hearing and cognition is present among individuals traditionally classified as having normal hearing.

Design, Setting, and Participants
Cross-sectional study of 2 US epidemiologic studies (Hispanic Community Health Study [HCHS], 2008-2011, and National Health and Nutrition Examination Study [NHANES], 1999-2000, 2001-2002, and 2011-2012 cycles). The dates of analysis were November 2018 to August 2019. Multivariable generalized additive model (GAM) regression and linear regression were used to assess the association between HL (exposure) and cognition (outcome). Participants included 6451 individuals aged 50 years or older from the general Hispanic population (HCHS [n = 5190]) and the general civilian, noninstitutionalized US population (NHANES [n = 1261]).

Exposures
Audiometric HL (4-frequency pure-tone average).

Main Outcomes and Measures
Neurocognitive performance measured by the Digit Symbol Substitution Test (DSST) (score range, 0-113), Word Frequency Test (range, 0-49), Spanish-English Verbal Learning Test (SEVLT) 3 trials (range, 5-40), SEVLT recall (range, 0-15), and Six-Item Screener (range, 0-6); higher scores indicated better cognitive performance.

Results
Among 6451 individuals, the mean (SD) age was 59.4 (6.1) years, and 3841 (59.5%) were women. The GAM regression showed a significant inverse association between hearing and cognition across the entire spectrum of hearing after adjusting for demographics and cardiovascular disease. In separate multivariable linear regressions stratified by the classic binary definition of HL, decreased hearing was independently associated with decreased cognition in adults with normal hearing (pure-tone average ≤25 dB) across all cognitive tests in the HCHS. For example in this group, a 10-dB decrease in hearing was associated with a clinically meaningful 1.97-point (95% CI, 1.18-2.75) decrease in score on the DSST. When using a stricter HL cut point (15 dB), an association was also present in NHANES. The associations between hearing and cognition were stronger or equivalent in individuals with normal hearing than among those with HL. For example, there was a 2.28-point (95% CI, 1.56-3.00) combined cohort DSST score decrease per 10-dB decrease among individuals with normal hearing vs a 0.97-point (95% CI, 0.20-1.75) decrease among those with HL, with a significant interaction term between continuous and binary hearing.

Conclusions and Relevance
An independent association was observed between cognition and subclinical HL. The association between hearing and cognition may be present earlier in HL than previously understood. Studies investigating whether treating HL can prevent impaired cognition and dementia should consider a lower threshold for defining HL than the current 25-dB threshold.

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