Summary: A longitudinal study finds that hearing impairment in older adults is linked to faster cognitive decline. Higher education appears to reduce this effect for mild hearing loss, but not for moderate-to-severe loss.
Source: UCSD
Hearing loss is a common consequence of aging, and its relationship to cognitive decline is an important public health concern. Nearly three-quarters of U.S. adults aged 70 and older have some degree of hearing impairment, but how this sensory loss affects long-term cognitive trajectories has remained unclear.
Researchers at the University of California San Diego School of Medicine examined this question in a large, long-running study of older, community-dwelling adults. Their results indicate that hearing impairment is associated with accelerated cognitive decline over time. Importantly, the negative impact of mild hearing impairment on cognition was reduced among participants with a college education, suggesting that educational attainment may provide some cognitive reserve against the effects of mild hearing loss.
The study, published in the Journal of Gerontology: Series A, followed 1,164 participants from the Rancho Bernardo Study of Healthy Aging. The group had a mean age of 73.5 years at baseline and was 64 percent female. All participants had hearing acuity and cognitive function assessed between 1992 and 1996 and then received up to five additional cognitive assessments over a period of as long as 24 years. None of the participants used hearing aids during the study period.
Hearing acuity was categorized using a standard pure-tone average (PTA) threshold: normal (PTA ≤25 dB), mild impairment (PTA >25–40 dB), and moderate-to-severe impairment (PTA >40 dB). Nearly half of the participants (49.8 percent) had mild hearing impairment, and 16.8 percent had moderate-to-severe impairment.
At the initial testing visit, participants with more severe hearing impairment performed worse on common cognitive measures, including the Mini-Mental State Exam (MMSE) and the Trail-Making Test Part B (Trails B). Over the full follow-up period, both mild and moderate-to-severe hearing impairment were associated with greater decline on these measures. In fully adjusted statistical models, mild hearing impairment and moderate-to-severe impairment were both linked to steeper deterioration in MMSE and Trails B scores, with stronger effects observed for the more severe category.
The study found a notable interaction between hearing impairment and education. Mild hearing loss was linked to faster MMSE decline among participants without a college degree, but this association was not observed among those with a college education. In contrast, moderate-to-severe hearing impairment predicted faster MMSE decline irrespective of educational level. The authors interpret this to mean that higher education may provide cognitive reserve sufficient to buffer the effects of mild hearing loss, but not the more pronounced impacts associated with greater hearing impairment.
Contrary to some prior hypotheses, degree of social engagement did not change the relationship between hearing loss and cognitive decline in this sample. First author Ali Alattar noted that this was somewhat unexpected, since social isolation has been proposed as one pathway linking hearing impairment to cognitive problems. In this cohort, participants with hearing impairment were as socially engaged as those without it.
These findings have practical implications for clinicians and public health. The authors recommend routine screening for hearing impairment in older adults, given its association with accelerated cognitive decline and the fact that hearing loss is often irreversible. Preventive actions—especially reducing exposure to loud noise, the primary modifiable risk factor for hearing loss—are emphasized as important across the lifespan.
Funding: Supported in part by the UC San Diego School of Medicine Clinical Research Fellowship and by National Institutes of Health funding.
Publication: Journal of Gerontology: Series A, published February 12, 2019. Article title: “Hearing impairment and cognitive decline in older, community-dwelling adults.”
Key findings summary:
- Hearing impairment is common in older adults and is associated with faster cognitive decline on standardized measures.
- Mild hearing impairment affected cognitive decline more among those without college education; higher education appeared protective for mild loss.
- Moderate-to-severe hearing impairment predicted cognitive decline regardless of education level.
- Social engagement did not modify the association in this cohort.
- Routine screening and preventive strategies—particularly reducing loud noise exposure—are recommended.
Background: Hearing impairment is prevalent among older adults and has been identified as a risk factor for cognitive impairment and dementia. This study evaluated the association of hearing impairment with long-term cognitive decline in community-dwelling older adults.
Methods: A population-based longitudinal study followed adults who did not use hearing aids, assessed for hearing acuity and cognitive function between 1992 and 1996, and followed for up to 24 years with repeat cognitive testing. Hearing was classified by pure-tone average into normal, mild, and moderate/severe impairment.
Results: Of 1,164 participants (mean age 73.5 years, 64% women), 49.8% had mild hearing impairment and 16.8% had moderate/severe impairment. Hearing impairment was associated with steeper decline on the MMSE and Trails B. The MMSE association with mild impairment was limited to participants without a college education; moderate/severe impairment was associated with steeper MMSE decline irrespective of education. Associations did not differ by sex or APOE ε4 status and were not influenced by social engagement.
Conclusions: Hearing impairment predicts accelerated cognitive decline in older adults and should be routinely screened for. Higher education may provide cognitive reserve that mitigates the effects of mild hearing loss but does not appear to offset the impact of moderate-to-severe impairment.
Original study authors include Ali A. Alattar, Jaclyn Bergstrom, Gail A. Laughlin, Donna Kritz-Silverstein, Erin L. Richard, Emilie T. Reas, Jeffrey P. Harris, Elizabeth Barrett-Connor, and Linda K. McEvoy. DOI: 10.1093/gerona/glz035