Hearing aid interventions to mitigate cognitive impairment: A critical review of the literature and meta-analysis

Aging-related hearing loss (ARHL) is epidemiologically linked to the development of Alzheimers Disease (AD). The mechanisms underlying this relationship are not known and have important therapeutic implications. If ARHL is causally linked to the development of AD, then correction of hearing loss via hearing aids should mitigate cognitive impairments in AD and more aggressive campaigns to treat ARHL, which is widely undertreated, would be warranted. Here, we critically examine the literature involving the use of hearing aids to treat ARHL and examine the impact of hearing aids on cognition. Although many studies report beneficial effects of hearing aids on cognition, most of these studies have significant flaws in their experimental design, making it difficult to judge their outcomes. In our selection process, we prioritized randomized studies and those with blinded and placebo-controlled outcomes. We evaluated a total of 10 papers that met inclusion criteria. Within our literature review, we found two randomized placebo-controlled studies that examined the impact of hearing aids on cognition in cognitively-impaired or vulnerable older individuals with minimal risk of bias. Meta-analysis of these two studies did not yield a statistically significant benefit of hearing aid use after 6 or 12 months of use. We propose that the current literature on this topic currently lacks compelling evidence to demonstrate that hearing aid use directly benefits cognition or delays AD. We further recommend strategies for improving clinical trial design to bring greater clarity to this important issue.