A Systematic Review and Meta-analysis re: Association of Age-Related Hearing Loss With Cognitive Function, Cognitive Impairment, and Dementia
- Adults with hearing loss experience a 30-40 percent faster decline in cognitive abilities*
- Adults with hearing loss are up to five times more likely to develop dementia*
- Hearing loss is linked to accelerated brain shrinkage*
Recently, a systematic review of dozens of these studies confirmed the link. It was published in February’s JAMA Otolaryngology-Head & Neck Surgery.
The review promotes new thinking that a preventative strategy for dementia — by reducing proven risk factors — may be more beneficial than post-diagnosis therapy. By treating hearing loss, you can play a role in mitigating one of the risk factors associated with dementia.
Question Is age-related hearing loss associated with an increased risk for cognitive decline, cognitive impairment, and dementia?
Findings In this systematic review and meta-analysis of 36 epidemiologic studies and 20 264 unique participants, age-related hearing loss was significantly associated with decline in all main cognitive domains and with increased risk for cognitive impairment and incident dementia. Increased risks for Alzheimer disease and vascular dementia were nonsignificant.
Meaning Age-related hearing loss is a possible biomarker and modifiable risk factor for cognitive decline, cognitive impairment, and dementia.
Importance Epidemiologic research on the possible link between age-related hearing loss (ARHL) and cognitive decline and dementia has produced inconsistent results. Clarifying this association is of interest because ARHL may be a risk factor for outcomes of clinical dementia.
Objectives To examine and estimate the association between ARHL and cognitive function, cognitive impairment, and dementia through a systematic review and meta-analysis.
Data Sources and Study Selection A search of PubMed, the Cochrane Library, EMBASE, and SCOPUS from inception to April 15, 2016, with cross-referencing of retrieved studies and personal files for potentially eligible studies was performed. Keywords included hearing, cognition, dementia, and Alzheimer disease. Cohort and cross-sectional studies published in peer-reviewed literature and using objective outcome measures were included. Case-control studies were excluded.
Data Extraction and Synthesis One reviewer extracted and another verified data. Both reviewers independently assessed study quality. Estimates were pooled using random-effects meta-analysis. Subgroup and meta-regression analyses of study-level characteristics were performed.
Main Outcomes and Measures Hearing loss measured by pure-tone audiometry only and objective assessment measures of cognitive function, cognitive impairment, and dementia. Cognitive function outcomes were converted to correlation coefficients (r value); cognitive impairment and dementia outcomes, to odds ratios (ORs).
Results Forty studies from 12 countries met our inclusion criteria. Of these, 36 unique studies with an estimated 20 264 unique participants were included in the meta-analyses. Based on the pooled maximally adjusted effect sizes using random-effects models, a small but significant association was found for ARHL within all domains of cognitive function. Among cross-sectional studies, a significant association was found for cognitive impairment (OR, 2.00; 95% CI, 1.39-2.89) and dementia (OR, 2.42; 95% CI, 1.24-4.72). Among prospective cohort studies, a significant association was found for cognitive impairment (OR, 1.22; 95% CI, 1.09-1.36) and dementia (OR, 1.28; 95% CI, 1.02-1.59) but not for Alzheimer disease (OR, 1.69; 95% CI, 0.72-4.00). In further analyses, study, demographic, audiometric, and analyses factors were associated with cognitive function. Vascular dysfunction and impaired verbal communication may contribute to the association between hearing loss and cognitive decline.
Conclusions and Relevance Age-related hearing loss is a possible bio-marker and modifiable risk factor for cognitive decline, cognitive impairment, and dementia. Additional research and randomized clinical trials are warranted to examine implications of treatment for cognition and to explore possible causal mechanisms underlying this relationship.