Dementia and hearing-aid use: a two-way street

Abstract

Objectives: Hearing-aid use may reduce risk of dementia, but cognitive impairment makes use more challenging. An observed association between reduced hearing-aid use and incident dementia could reflect either or both of these causal paths. The objective was to examine the effects of each path while minimising contamination between paths.

Methods: Health records data from 380,794 Veterans who obtained hearing aids from the US Veterans Affairs healthcare system were analysed. Analysis 1 (n = 72,180) used multivariable logistic regression to model the likelihood of incident dementia 3.5-5 years post hearing-aid fitting for patients free of dementia and mild cognitive impairment (MCI). Analysis 2 (n = 272,748) modelled the likelihood of being a persistent hearing-aid user at 3 years 2 months after fitting, contrasting subgroups by level of cognitive function at the time of fitting. Analysis time windows were optimized relative to dataset constraints. Models were controlled for available relevant predictors.

Results: The adjusted OR for incident dementia was 0.73 (95% CI 0.66-0.81) for persistent (versus non-persistent) hearing-aid users. The adjusted OR for hearing-aid use persistence was 0.46 (95% CI 0.43-0.48) in those with pre-existing dementia (versus those remaining free of MCI and dementia).

Conclusion: Substantial independent associations are observed in both directions, suggesting that hearing-aid use decreases risk of dementia and that better cognitive function predisposes towards persistent use. Research studying protective effects of hearing-aid use against dementia needs to account for cognitive status. Clinically, hearing devices and hearing care processes must be accessible and usable for all, regardless of their cognitive status.

Keywords: causality; dementia; hearing aid; older people; persistence.

Figure 1

Flowcharts showing the criteria used to determine patient inclusion and resulting Ns for analysis 1 (left) and analysis 2 (right). See text for further explanation.

Figure 2

Visualisation of raw data (filled symbols) and adjusted regression models (stroke symbols) for analyses 1 and 2. Numbers indicate N for each data point. Patients aged 100+ not shown (N < 20). (A) Dementia incidence at 3.5 to 5 years post hearing-aid fitting for 72,180 patients free of dementia and MCI prior to 3.5 years post hearing-aid fitting. Adjusted model datapoints were obtained by assigning each patient their probability of incident dementia predicted by the model, then averaging in each patient age group.   and  , persistent;   and  , non-persistent hearing-aid users at 3.5 years post fitting. (B): Hearing-aid use persistence at 3 years 2 months post hearing-aid fitting for 272,748 patients. Adjusted model datapoints were obtained by assigning each patient their probability of hearing-aid use persistence predicted by the model, then averaging in each patient age group.   and  , prevalent-dementia group (prevalent dementia at time of hearing-aid fitting);   and  , high-functioning group (no dementia or MCI at any time up to 31 December 2017).