1. The use of a restorative hearing aid in patients with hearing loss reduced the risk of developing dementia by 19%.
2. Hearing aid use was associated with a 3% increase in cognitive test scores.
Assessment of the level of proof: 1 (Excellent)
Summary of the study: Hearing loss is a common and undertreated condition, especially in elderly patients. It is a known risk factor for developing dementia, as well as other conditions affecting perception. Thanks to technologies such as cochlear implants and other hearing restoration devices, hearing loss is modifiable. This study aimed to determine the effect of hearing loss treatment on patients’ risk of developing dementia and cognitive changes.
The original systematic search yielded 3243 studies, of which 31 eligible studies were included in the qualitative analysis and 18 in the quantitative meta-analysis. Eight studies were included in the meta-analysis of longitudinal assessment (2-25 years) of hearing loss and cognitive function. All studies favored the treatment of hearing loss with a pooled overall estimate of a 19% reduction in risk. Use of restorative hearing aids protected against cognitive decline, re-diagnosis of dementia, and decline in cognitive function from mild impairment to dementia. Finally, analysis of studies assessing absolute cognitive test scores demonstrated a 3% increase in cognitive function from baseline in hearing-impaired patients after starting to use a restorative hearing aid.
The present study by Yeo et al. demonstrated a significant benefit to hearing loss treatment using restorative devices in protecting against cognitive decline. This work is important for quantifying the benefits of restorative hearing aids and may influence funding for this technology for patients with hearing loss. The design of the study and a considerable number of included studies are a major advantage with regard to the strength of the results reported. A main limitation of this study is the inability to compare the severity of hearing loss among the patients included. As such, it is impossible to know whether the effect of hearing restoration devices differs depending on the basic function. Future studies should seek to determine the feasibility of implementing hearing aid solutions at the systems level.
Click here to read this study in JAMA Neurology
Click to read an accompanying editorial in JAMA Neurology
Relevant reading: Hearing loss and risk of dementia later in life
In depth [systematic review and meta-analysis]: A systematic review and meta-analysis were conducted, registered first on PROSPERO. Three databases were searched (PubMed, Embase and the Cochrane Library) for all primary or randomized controlled observational studies of cognitive decline in patients with treated hearing loss. The main outcomes of interest were the diagnosis of dementia or generalized cognitive decline measured by standard tests. Risk of bias assessments were performed using the Ottawa-Newcastle scale, and overall publication bias was determined using funnel plots as well as Egger’s statistical test.
Of the 31 included studies, 2 were randomized controlled trials, 16 were prospective cohort studies, and the others were retrospective or cross-sectional. Twenty-one studies were at moderate risk and 10 were at low risk of bias. The severity of hearing loss was variable among the included participants.
The hazard ratio for any cognitive decline in patients with treated hearing loss and longitudinal follow-up greater than 2 years was 0.81 (95% confidence interval 0.76-0.87). This estimate was based on 8 studies and a pooled group of 126,903 participants. This protective hazard ratio was consistent even when controlling for a number of possible confounders. The meta-analysis also revealed that patients treated with restorative hearing aids were also protected against other forms of cognitive decline: any cognitive impairment (relative risk 0.79, 95% confidence interval 0.65-0, 97), transition from moderate cognitive impairment to dementia (0.73, 0.60-0.88), a new diagnosis of dementia (0.83, 0.77-0.90). A pooled analysis of studies assessing absolute cognitive test scores demonstrated a 3% increase (ratio of means 1.03, 95% confidence interval 1.02-1.04) in cognitive function from baseline in hearing-impaired patients after starting to use a restorative hearing aid.
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