With no truly effective treatment for dementia yet available, there is increased interest in lifestyle factors that may delay or prevent the onset of dementia. Previous studies have shown that hearing loss is associated with increased risk of dementia and cognitive decline. There are 3 main hypotheses for this association: The Common Cause Hypothesis; The Cognitive Load Hypothesis; and the Cascade or Sensory Deficit Hypothesis (Figure). In this systematic review and meta-analysis of 31 studies involving nearly 140,000 subjects by Yeo and colleagues, it was determined that correcting hearing loss with cochlear implants or hearing aids may lead to both short- and long-term reductions in risk for cognitive decline. In the short-term, use of hearing restorative devices led to a 3% improvement in general cognition, and in the long-term, there was a 19% reduction in risk of cognitive decline. These data are very encouraging and promote the early detection (and correction) of hearing loss.

Figure: A. The Common Cause Hypothesis posits that both hearing loss and cognitive decline are due to the same neurodegenerative process. B. The Cascade Hypothesis or Sensory Deficit Hypothesis proposes that auditory deprivation leads to cognitive decline via decreased socialization, depression, and reduced sensory input. C. The Cognitive Load Hypothesis suggests that hearing loss diverts cognitive resources from memory functions to auditory processing. The three hypotheses (Common Cause, Cascade, and Cognitive Load) are not necessarily mutually exclusive; each may play a role in the connection between hearing loss and dementia. Therefore, hypothetically, treating hearing loss (e.g., with cochlear implants or hearing aids) may potentially help prevent, or delay the onset of, dementia. (Stahl’s Illustrated Alzheimer’s Disease and Other Dementias, 2018)

References:

Yeo BSY et al. JAMA Neurology 2022; Epub ahead of print. Abstract

Stahl SM, Morrissette DA. Stahl's Illustrated Alzheimer's Disease and Other Dementias. New York, NY: Cambridge University Press. 2018.