Untreated hearing loss increases dementia risk in middle-aged and older adults, new research confirms.
A large observational study from the United Kingdom showed a 42% increased risk for dementia in people with hearing loss compared with their peers with no hearing trouble. In addition, there was no increased risk in those with hearing loss who used hearing aids.
"The evidence is building that hearing loss may be the most impactful modifiable risk factor for dementia in mid-life, but the effectiveness of hearing aid use on reducing the risk of dementia in the real world has remained unclear," Dongshan Zhu, PhD, with Shandong University, Jinan, China, said in a news release.
"Our study provides the best evidence to date to suggest that hearing aids could be a minimally invasive, cost-effective treatment to mitigate the potential impact of hearing loss on dementia," Zhu said.
The study which was published online April 13 in Lancet Public Health, comes on the heels of the 2020 Lancet Commission report on dementia, which suggested hearing loss may be linked to approximately 8% of worldwide dementia cases, as reported by Medscape Medical News.
For the study, investigators analyzed longitudinal data on 437,704 individuals, most of whom were White, from the UK Biobank (54% female; mean age at baseline, 56 years).
Roughly three quarters of the cohort had no hearing loss and one quarter had some level of hearing loss, with 12% of these individuals using hearing aids.
After the researchers controlled for relevant co-factors, compared with people without hearing loss, those with hearing loss who were not using hearing aids had an increased risk for all-cause dementia (hazard ratio [HR], 1.42; 95% CI, 1.29-1.56).
No increased risk was seen in people with hearing loss who were using hearing aids (HR, 1.04; 95% CI, 0.98-1.10).
The positive association of hearing aid use was observed in all-cause dementia and cause-specific dementia subtypes, including Alzheimer's disease, vascular dementia, and non–Alzheimer's disease nonvascular dementia.
The data also suggest that the protection against dementia conferred by hearing aid use most likely stems from direct effects from hearing aids rather than indirect mediators, such as social isolation, loneliness, and low mood.
Zhu said the findings highlight the "urgent need" for the early use of hearing aids when an individual starts having trouble hearing.
"A group effort from across society is necessary, including raising awareness of hearing loss and the potential links with dementia; increasing accessibility to hearing aids by reducing cost; and more support for primary care workers to screen for hearing impairment, raise awareness, and deliver treatment such as fitting hearing aids," Zhu said.
Writing in a linked comment, Gill Livingston, MD, and Sergi Costafreda, MD, PhD, with University College London, note that with addition of this study, "the evidence that hearing aids are a powerful tool to reduce the risk of dementia in people with hearing loss, is as good as possible without randomized controlled trials, which might not be practically possible or ethical because people with hearing loss should not be stopped from using effective treatments."
"The evidence is compelling that treating hearing loss is a promising way of reducing dementia risk. This is the time to increase awareness of and detection of hearing loss, as well as the acceptability and usability of hearing aids," Livingston and Costafreda add.
High-Quality Evidence -- With Caveats
Several experts offered perspective on the analysis in a statement from the UK-based nonprofit Science Media Centre, which was not involved with the conduct of this study.
Charles Marshall, MRCP, PhD, with Queen Mary University of London, said that the study provides "high-quality evidence" that those with hearing loss who use hearing aids are at lower risk for dementia than are those with hearing loss who do not use hearing aids.
"This raises the possibility that a proportion of dementia cases could be prevented by using hearing aids to correct hearing loss. However, the observational nature of this study makes it difficult to be sure that hearing aids are actually causing the reduced risk of dementia," Marshall added.
"Hearing aids produce slightly distorted sound, and the brain has to adapt to this in order for hearing aids to be helpful," he said.
"People who are at risk of developing dementia in the future may have early changes in their brain that impair this adaptation, and this may lead to them choosing to not use hearing aids. This would confound the association, creating the appearance that hearing aids were reducing dementia risk, when actually their use was just identifying people with relatively healthy brains," Marshall added.
Tara Spires-Jones, PhD, with the University of Edinburgh, said this "well-conducted" study confirms previous similar studies showing an association between hearing loss and dementia risk.
Echoing Marshall, Spires-Jones noted that this type of study cannot prove conclusively that hearing loss causes dementia.
"For example," she said, "it is possible that people who are already in the very early stages of disease are less likely to seek help for hearing loss. However, on balance, this study and the rest of the data in the field indicate that keeping your brain healthy and engaged reduces dementia risk."
Spires-Jones said that she agrees with the investigators that it's "important to help people with hearing loss to get effective hearing aids to help keep their brains engaged through allowing richer social interactions."
This study was funded by the National Natural Science Foundation of China and Shandong Province, Taishan Scholars Project, China Medical Board, and China Postdoctoral Science Foundation. Zhu, Livingston, Costafreda, Marshall, and Spires-Jones have no relevant disclosures.