Treating Hearing Loss With Hearing Aids for the Prevention of Cognitive Decline and Dementia

BACKGROUND AND OBJECTIVES: Hearing loss is a risk factor of cognitive decline and dementia. We sought to investigate the effect of hearing aid (HA) use on cognition and dementia risk in older adults with hearing impairment.

METHODS: We emulated a target trial using data from Australian participants of the ASPirin in Reducing Events in the Elderly study. In the target trial, eligible participants were dementia-free, had moderate hearing impairment, and had no previous HA use. The treatment strategies were "use HAs" and "do not use HAs." Outcomes included overall cognition, dementia (DSM-IV criteria), and cognitive impairment (cognitive decline or dementia). The emulation used new HA prescription and frequency-of-use data measured by questionnaire, as well as cognition data from semiannual assessments over 7 years. Self-reported hearing problems were used as a proxy for moderate hearing impairment. Using the parametric g-formula, we estimated observational analogs of the intention-to-treat effect, using HA prescription to emulate allocation. Analyses for cognition outcomes were restricted to survivors. Multiple imputation was used for missing covariate and cognitive outcome data. We also emulated a second target trial with treatment strategies of (1) never, (2) rarely/sometimes, and (3) often/always use HAs.

RESULTS: Across imputed data sets, a median of 2,777 eligible individuals were included, with a median of 664 receiving a new HA prescription. The mean age was 75 years, and 48% were female. The estimated 7-year mean overall cognition scores among survivors were similar under HA prescription and no HA prescription (mean difference 0.03 SDs; 95% CI -0.14 to 0.21). The estimated 7-year risk of dementia was 5.0% under HA prescription and 7.5% under no HA prescription (risk ratio [RR] 0.67; 95% CI 0.37-0.97), and that of cognitive impairment was 36.1% under HA prescription and 42.4% under no HA prescription (RR 0.85; 95% CI 0.70-1.00). The risks of dementia and cognitive impairment were inversely associated with the frequency of HA use.

DISCUSSION: We found that HA use in older people with hearing impairment may reduce dementia risk, although differences in age-related cognitive change were insubstantial. We cannot rule out residual confounding as an explanation for our findings. Long-term randomized trials of HAs for dementia risk are justified.

CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that the use of hearing aids did not change overall cognitive scores in people 70 years and older with moderate hearing impairment as compared to those who used hearing aids.