Hearing loss affects approximately five percent of the world's population (WHO, 2015 http://bit.ly/2gAVBAk). As hearing loss is reported to be associated with social isolation, fatigue, depression, dementia, brain atrophy, and poorer physical and mental health, it is imperative to explore effective interventions to reduce or reverse these negative effects, particularly for the ever-increasing geriatric population in the world.
Using amplification devices to compensate for the loss of hearing sensitivity is one logical intervention. Yet, literature fails to support the effectiveness of such interventions, especially when taking into account the covariates of user characteristics (Int J Audiol. 2015;54:838 http://bit.ly/2gAVF38;J Am Geriatr Soc. 2015;63:2099 http://bit.ly/2gB1JIU). At this point, the general consensus in the scientific community is that both hearing loss and cognitive function are affected by an unknown factor(s) and, therefore, the improvement of hearing sensitivity does not directly effect a change in cognitive function. In addition, the use of hearing aids can improve specific cognitive functions such as working memory, but not general cognition, which encompasses many aspects of mental functions and capabilities.
While most research on amplification and cognitive function used hearing aids without auditory or cognitive training, emerging evidence shows that the combination of cochlear implantation and auditory and cognitive training may generate a different effect pattern. Mosnier and colleagues provided speech and cognitive training to elderly patients after cochlear implantation (JAMA Otolaryngol Head Neck Surg. 2015;141:442 http://bit.ly/2gAZRzQ). The authors reported improvements in users’ cognitive function, communication ability, depression ratings, and quality of life. It would be interesting to examine studies that include both hearing aid and cochlear implant users with and without auditory training.
USE OF HEARING AIDS OR COCHLEAR IMPLANTS AND DEPRESSIVE SYMPTOMS IN OLDER ADULTS
Choi, et al., conducted a prospective study to track depression symptoms on 63 hearing aid and 50 cochlear implant users who are aged 50 years or older and did not receive auditory training (JAMA Otolaryngol Head Neck Surg. 2016;142:652 http://bit.ly/2gB1kGr). The hearing aid participants were either new hearing aid users or previous hearing aid users who had used their hearing aids for less than an hour. All cochlear implant participants received their implants for the first time and reported verbal communication as their primary form of communication. All participants received routine clinical care, during which the participants and their audiologists determined the appropriate hearing technology (hearing aid or cochlear implant).
The participants'cognitive function was assessed using the 15-item Geriatric Depression Scale (GDS) before intervention (baseline), and at six and 12 months after intervention. The answer to each item is “yes” or “no” with a total of 15 possible points. Those who scored >5 are considered to have varying degrees of depression.
All statistical analyses were conducted with adjustments for age, sex, educational level, and history of hypertension, diabetes, and smoking. A confidence interval of 95 percent was used for statistical significance.
As a group, hearing aid users obtained GDS scores of 1.5, 1.1, and 1.3, and cochlear implant participants obtained GDS scores of 2.6, 1.8, and 1.6 at baseline, and at six and 12 months post-intervention respectively. Statistical analyses indicated that only the GDS scores at six months (not at 12 months) were significantly different from the baseline for hearing aid users, whereas scores at both six and 12 months post-intervention were significantly different from the baseline for cochlear implant users. While these results suggest a different treatment outcome pattern between cochlear implant and hearing aid participants, it is likely that both statistical differences were clinically insignificant due to the floor effect.
It is unclear whether the cochlear implant participants received auditory training as part of their clinical services for cochlear implantation and whether the higher attrition rate of hearing aid users at 12 months affected the outcome. A positive outcome of the study is that eight cochlear implant and five hearing aid participants had >5 scores at baseline, but these numbers were reduced by two in both groups at 12 months post-intervention.
AUDITORY REHABILITATION AND TRAINING WITH HEARING AIDS AND COCHLEAR IMPLANTS ON COGNITIVE FUNCTION AND DEPRESSION AMONG OLDER ADULTS
Castiglione and colleagues conducted a prospective study to examine the effects of amplification and auditory training (Audiol Neurotol. 2016;21[suppl 1]:21 http://bit.ly/2gB1gq9). They divided 125 participants into six groups:
- New bilateral hearing aid users with one month of auditory training (unaided thresholds: moderate – severe)
- Bilateral hearing aid users with training (unaided thresholds: moderate – severe)
- Unilateral hearing aid users with training
- Non-hearing aid users with no training (unaided thresholds: mild – moderate)
- Cochlear implant users with training
- Normal hearing participants with no training
Several tests were used to assess different cognitive and mental functions:
- Montreal Cognitive Assessment – cognitive functions
- Geriatric Depression Scale – depression
- Digit Span Test – short-term memory
- Stroop Color-Word Test – executive function, reaction time, and selective attention
The results showed that new hearing aid users (Group A) showed significant improvement in short-term memory after using hearing aids for one month. The experienced hearing aid users (Group B) had better short-term memory in the aided condition than the unaided condition. Although no difference was found in executive function in the two conditions, Group B had lower reaction times in the aided condition. Unilateral hearing aid users (Group C) and normal hearing controls (Group F) had significantly higher cognitive function and lower depression scores than non-hearing aid users (Group D). Cochlear implant users (Group E) displayed significant reduction in depression and improvement in cognitive function one year after implantation. Those with higher cognitive functions tend to have lower aided pure-tone thresholds, better speech recognition thresholds, lower depression scores, and a younger age. There was no statistically significant difference in cognitive functions among Groups C, E, and F at the conclusion of this study.
An integration of the results of the two studies suggests that although a sustained positive effect was not observed in mere improvement of hearing sensitivity, auditory training and active learning could promote long-term positive effects on improving cognitive and mental functions.
Association of Using Hearing Aids or Cochlear Implants With Changes in Depressive Symptoms in Older Adults
Choi JS, Betz J, Li L, et al.
JAMA Otolaryngol Head Neck Surg
Aging, Cognitive Decline and Hearing Loss: Effects of Auditory Rehabilitation and Training With Hearing Aids and Cochlear Implants on Cognitive Function and Depression Among Older Adults
Castiglione A, Benatti A, Velardita C, et al.
2016;21(suppl 1):21 http://bit.ly/2gB1gq9