A new systematic review and meta-analysis published in Ageing Research Reviews examined the relationship between adult-onset hearing loss and cognitive impairment. Analyzing data from fifty cohort studies involving over 1.5 million participants, the study suggests that hearing loss significantly increases the risk of cognitive decline, dementia, and Alzheimer’s disease (AD).
Hearing loss is a major global health issue affecting an estimated 1.5 billion people worldwide, a number that is expected to rise with the aging population. The World Health Organization and the Lancet Commission on Dementia have identified hearing loss as a potentially modifiable risk factor for dementia, suggesting that treatments like hearing aids might prevent or delay cognitive decline.
“…this meta-analysis of cohort studies provided compelling evidence across diverse study settings and designs of adult-onset hearing loss being a robust and consistent independent risk factor for dementia.”
Hearing Loss and Dementia Risk
This comprehensive review aimed to summarize existing cohort evidence on adult-onset hearing loss as a risk factor for cognitive impairment and dementia. The study explored the dose-response relationship, risk for various dementia subtypes, and potential moderators that might influence this association.
The researchers included cohort studies with participants who had no dementia at baseline, assessed hearing at the beginning of the study, and followed them for at least two years. They used random-effect models and conducted subgroup and meta-regression analyses to examine the impact of different moderators.
Key Findings
The analysis included fifty studies with a total of 1,548,754 participants. The findings revealed that:
- Increased Dementia Risk: Hearing loss was associated with a 35% increased risk of incident dementia (HR=1.35), a 29% increased risk of mild cognitive impairment (MCI) (HR=1.29), and a 56% increased risk of Alzheimer’s disease dementia (HR=1.56). However, the association with vascular dementia was not statistically significant (HR=1.30).
- Dose-Response Relationship: Each 10-decibel worsening of hearing was linked to a 16% increase in dementia risk, indicating a dose-response relationship where greater hearing loss correlates with higher dementia risk.
- Consistency Across Subtypes: The impact of hearing loss on dementia risk did not vary significantly across different types of dementia or other moderators such as baseline age or cardiovascular health.
The findings support the hypothesis that adult-onset hearing loss is a significant risk factor for cognitive decline and dementia. The study’s extensive data and robust methodology provide further evidence that this association is consistent across different populations and study designs.
The research suggests several possible mechanisms for this link, including reduced social interaction and accelerated brain pathology due to hearing loss. However, the potential for residual confounding factors such as age and cardiovascular health cannot be entirely ruled out.
Implications
The study’s findings underscore the importance of early identification and treatment of hearing loss, potentially through the use of hearing aids, as a strategy to reduce the risk of cognitive decline and dementia. This emphasizes the need for regular hearing assessments, particularly in older adults, and integrating hearing care into broader dementia prevention strategies.
“…Adult-onset hearing loss is also potentially treatable, most often with hearing aids. Our findings suggest that this treatment may also reduce dementia risk.”
Despite the large participant pool and diverse settings, variations in hearing and cognitive assessment methods, follow-up durations, and analysis techniques introduced some residual heterogeneity, suggesting that other unexamined factors might also play a role. Nonetheless, the systematic review and meta-analysis provide strong evidence that adult-onset hearing loss is a significant and independent risk factor for dementia.
Addressing hearing loss through interventions like hearing aids could mitigate this risk, highlighting the need to incorporate hearing loss management into public health strategies to reduce the incidence of dementia and cognitive impairment.
Reference:
- Yu, R.-C., Proctor, D., Soni, J., Pikett, L., Livingston, G., Lewis, G., Schilder, A., Bamiou, D., Mandavia, R., Omar, R., Pavlou, M., Lin, F., Goman, A. M., & Costafreda Gonzalez, S. (2024). Adult-onset hearing loss and incident cognitive impairment and dementia – A systematic review and meta-analysis of cohort studies. Ageing Research Reviews, 102346. ISSN 1568-1637. https://doi.org/10.1016/j.arr.2024.102346.
