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Moderate-to-severe hearing loss was linked with a higher prevalence of dementia, a cross-sectional study of Medicare beneficiaries showed.

Among 2,413 older adults in the National Health and Aging Trends Study (NHATS), dementia prevalence among people with moderate-to-severe hearing loss was higher than it was among people with normal hearing (prevalence ratio 1.61, 95% CI 1.09-2.38), reported Nicholas Reed, AuD, of the Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues.

But among people with moderate-to-severe hearing loss in the study, hearing aid use was associated with a lower prevalence of dementia compared with no hearing aid use (prevalence ratio 0.68, 95% CI 0.47-1.00), they wrote in a .

The findings support a recent systematic review and meta-analysis that showed treating hearing loss led to cognitive benefits. They also support the availability of over-the-counter hearing aids, which people with mild-to-moderate hearing loss now can purchase directly due to .

Reed and colleagues used data from the continuous panel study of Medicare beneficiaries. The NHATS cohort was oversampled for age (53.3% were 80 or older) and race (18.8% were Black). Participant information collected through in-home interviews.

Hearing was assessed with a portable audiometer. Researchers calculated a pure tone average in the better-hearing ear as the mean of four frequencies -- 500, 1,000, 2,000, and 4,000 Hz -- most important for understanding speech.

Normal hearing was defined as a pure tone average of 25 dB or less, mild hearing loss was 26-40 dB, and moderate-to-severe loss was over 40 dB. About a third of participants (33.47%) had normal hearing after weighting; 36.74% had mild hearing loss, and 29.79% had moderate-to-severe loss. People with moderate-to-severe hearing loss tended to be older, male, and white, and had less education than others.

The weighted prevalence of dementia was 10.27% overall. Dementia prevalence rose as severity of hearing loss increased: for normal hearing, it was 6.19%; for mild hearing loss, it was 8.93%; and for moderate-to-severe hearing loss, it was 16.52%.

The study's cross-sectional design was a limitation. In addition, nursing home and residential care residents were excluded from the analysis because the researchers did not have cognitive data about them.

The top modifiable risk factor for dementia prevention is hearing loss, which accounts for 8% of the global dementia burden according to a recent Lancet Commission report.

"This study refines what we've observed about the link between hearing loss and dementia, and builds support for public health action to improve hearing care access," co-author Alison Huang, PhD, also of Johns Hopkins, said in a statement.

How hearing loss is linked to dementia isn't clear and studies point to several possible mechanisms. "Mediation analyses to characterize mechanisms underlying the association and randomized trials to determine the effects of hearing interventions on reducing dementia risk are needed," Reed and colleagues wrote.

Information about hearing loss treatment and cognition from the 3-year randomized trial is expected later this year.

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