ENHANCE: a comparative prospective longitudinal study of cognitive outcomes after 3 years of hearing aid use in older adults

Abstract

Background: With an aging population, the prevalence of hearing loss and dementia are increasing rapidly. Hearing loss is currently considered the largest potentially modifiable risk factor for dementia. The effect of hearing interventions on cognitive function should therefore be investigated, as if effective, these may be successfully implemented to modify cognitive outcomes for older adults with hearing loss.

Methods: This prospective longitudinal observational cohort study compared outcomes of a convenience sample of prospectively recruited first-time hearing aid users without dementia from an audiology center with those of community-living older adults participating in a large prospective longitudinal cohort study with/without hearing loss and/or hearing aids. All participants were assessed at baseline, 18 months, and 36 months using the same measures.

Results: Participants were 160 audiology clinic patients (48.8% female patient; mean age 73.5 years) with mild-severe hearing loss, fitted with hearing aids at baseline, and 102 participants of the Australian Imaging, Biomarkers and Lifestyle Flagship Study of Aging (AIBL) (55.9% female patient; mean age 74.5 years). 18- and 36-month outcomes of subsets of the first participants to reach these points and complete the cognition assessment to date are compared. Primary comparative analysis showed cognitive stability for the hearing aid group while the AIBL group declined on working memory, visual attention, and psychomotor function. There was a non-significant trend for decline in visual learning for the AIBL group versus no decline for the hearing aid group. The hearing aid group showed significant decline on only 1 subtest and at a significantly slower rate than for the AIBL participants (p < 0.05). When education effects on cognitive trajectory were controlled, the HA group still performed significantly better on visual attention and psychomotor function (lower educated participants only) compared to the AIBL group but not on working memory or visual learning. Physical activity had no effect on cognitive performance trajectory.

Conclusion: Hearing aid users demonstrated significantly better cognitive performance to 3 years post-fitting, suggesting that hearing intervention may delay cognitive decline/dementia onset in older adults. Further studies using appropriate measures of cognition, hearing, and device use, with longer follow-up, are required.

Keywords: cognitive performance; delay; dementia; hearing aids; hearing loss; intervention; risk factor.

Figure 1

Comparative cognitive performance over 36 months for the HA and AIBL groups on the Cogstate Brief Battery. Scoring is based on speed and accuracy; therefore, increased scores indicate poorer performance. Relative to HA participants, scores for AIBL participants increased over time, while those for HA participants remained relatively stable.

Figure 2

Estimated mean trajectories of cognitive change over 36 months, controlling for education, on the Cogstate Brief Battery visual attention subtest. Trajectories are net of individual specific characteristics that influence baseline cognitive performance. The x-axis shows days since baseline. The y-axis shows primary outcome raw scores. All baselines have a zero mean by construction as mean individual fixed effects have been subtracted out. AIBL participants are deteriorating significantly faster than HA participants (note reverse scoring means increasing scores indicate worse performance). After controlling for education, lower and higher educated participants in the HA group performed significantly better on visual attention than both lower and higher educated AIBL group participants.

Figure 3

Estimated mean trajectories of cognitive change over 36 months, controlling for education, on the Cogstate Brief Battery working memory subtest. Trajectories are net of individual specific characteristics that influence baseline cognitive performance. The x-axis shows days since baseline. The y-axis shows primary outcome raw scores. All baselines have a zero mean by construction as mean individual fixed effects have been subtracted out. AIBL participants are deteriorating significantly faster than HA participants (note reverse scoring means increasing scores indicate worse performance). When education was controlled, higher educated HA participants performed significantly better than higher educated AIBL participants.

Figure 4

Estimated mean trajectories of cognitive change over 36 months, controlling for education, on the Cogstate Brief Battery psychomotor function subtest. Trajectories are net of individual specific characteristics that influence baseline cognitive performance. The x-axis shows days since baseline. The y-axis shows primary outcome raw scores. All baselines have a zero mean by construction as mean individual fixed effects have been subtracted out. AIBL participants are deteriorating significantly faster than HA participants (note reverse scoring means increasing scores indicate worse performance). After controlling for education, lower educated participants in the HA group performed significantly better on psychomotor function than lower educated AIBL group participants.