Hearing loss is a common experience for older adults and is one of the leading causes of nonfatal disease burden for Australians aged 65 years and older [1,2]. Sensorineural hearing loss or presbycusis is the most prevalent hearing-related chronic condition affecting this population; however, it is often underdetected and undertreated. This type of hearing loss cannot be medically or surgically treated [3-6]. The number of adults who suffer from sensorineural hearing loss worldwide is likely to increase rapidly as the population ages [7].

Recent studies have reported that hearing loss among older adults is strongly and independently associated with accelerated cognitive decline [8-13]. Epidemiologic and longitudinal studies have demonstrated that older people aged between 70 and 79 years with hearing impairment, who live in the community, have a 24% increased risk of a decline in cognitive function and may experience a 30% to 40% higher rate of cognitive decline over a 6-year period than those without hearing loss [9,14,15]. The proposed theories to explain the above association relate to the effects of hearing loss on cognitive load and cognition reserve, and the effects of hearing impairment on brain structure and shared pathologic etiology, social isolation, and depressive symptoms [13]. Social isolation and communication impairments caused by hearing loss are known to lead to loneliness and depression in older adults [16,17], often resulting in a negative perception of one’s own health and a decline in daily activities, with associated declines in cognitive performance.

In aural rehabilitation, hearing aid use and auditory training strategies contribute to improving auditory abilities. The basic function of hearing aids is acoustic amplification of sound signals with the aim of restoring the audibility of sounds, thus helping to improve speech perception [18]. Studies have examined the effects of hearing aid use by older adults on a broad range of cognitive functions, such as information-processing speed, memory, and verbal fluency. Preliminary research evidence has suggested that hearing aids may improve the cognitive abilities, social, emotional, psychological, and physical well-being of people [18-21]. Some studies reporting the cognitive and psychological benefits of using hearing aids in elderly people have shown that the effects of hearing aid use are most distinctive in the early periods of use [6]. Despite the high prevalence of hearing loss in older adults, and the consequences for health outcomes, people are generally slow to acquire hearing aids [22]. Less than 25% of people who would benefit from hearing aids actually own them [23]. Existing research in this area, attempting to describe the effects of hearing aids on cognition, often assessed global mental status rather than cognitive performance and often examined only a single measure of hearing [6,19,24], thus limiting the insights gained. These studies also lack data on the duration of hearing impairment and loosely define hearing aid use as the self-reported use of a hearing aid in either or both ears, thus making it unclear about how hearing loss may affect performance on measures of cognition.

Auditory training is the use of instruction, drill, or practice, designed to increase the amount of information that hearing contributes to a person’s total perception [25]. For example, a person with a hearing impairment who is fitted with a new hearing aid may benefit from instruction and practice in recognizing sounds through the aid. Research has shown that new hearing aid users show greater benefit from auditory training than experienced hearing aid users [26]. Auditory training also shares processes in common with cognitive training for improving working memory, attention, and communication. Studies have shown that auditory training can produce prolonged cognitive performance improvements [27,28] and improve speech understanding [29,30]. Other studies have shown that the benefits of training for people with hearing loss in terms of improved speech understanding are best achieved if an integrated auditory-cognitive training approach is adopted [31].

Although the concept of auditory training is not new, its popularity has declined in recent years, and only a small proportion of audiologists (fewer than 10%) offer auditory training to patients with hearing impairment [32]. Also, limited auditory training effort has been directed toward adults with impaired hearing, and the focus of auditory training has historically been directed toward young children with profound or severe to profound hearing loss [33,34].

Studies have investigated the effects of auditory training with laptops and computers, such as with the Listening and Communication Enhancement (LACE) software, on generalization to speech perception, self-report of communication difficulties, and cognition [27,28,33]. The results of these studies have often demonstrated the efficacy of auditory training, despite the computerized method of auditory training perhaps resulting in lower compliance with training protocols [32]. In addition, Saunders et al [35] found that LACE training did not result in improved outcomes over a standard-care hearing aid intervention on its own. Furthermore, according to research studies [36,37], there are still a large number of outstanding questions on the benefits of auditory training, such as which aspects of auditory training protocols contribute to learning, how auditory training generalizes to benefits in everyday communication, how individual characteristics interact with training outcomes to identify candidacy for auditory training, and the identification of outcome measures that are appropriate and sufficiently sensitive.

Research has shown that hearing aid devices alone do not always adequately compensate for sensory losses despite significant technological advances in digital technology [38]. Therefore, the focus of intervention will consider face-to-face auditory training in conjunction with a hearing aid device, whereas the comparator (control) group will consider individualized face-to-face auditory training on its own.

Extending upon preliminary findings [27,28,36], the objective of this study is to investigate whether wearing hearing aids will improve the impact of individualized face-to-face auditory training on cognition, depression, and social interaction for adults with sensorineural hearing loss in a crossover intervention trial.

The study is based on the following hypotheses:

This study has a randomized crossover trial design. It attained ethics approval on July 22, 2016 (Swinburne’s Human Research Ethics Committee protocol number SHR Project 2016/159).

All participants will undergo an individualized face-to-face auditory training program for a period of 6 months and will be randomly allocated to one of the following groups:

Participants will be tested at baseline, and at 3 and 6 months in terms of cognition, depressive symptoms, social interaction, and hearing satisfaction.

A crossover design is chosen to allow each participant to serve as their own control [39]. Group A participants will have the option to withdraw from the study after 3 months if they decide to purchase hearing aids immediately. Similarly, group B participants will also have the option of withdrawing from the study at any time. As all participants will receive auditory training for the entire duration of the study to address their hearing loss, participants will benefit from the study even when the hearing aid intervention is not in place.

This study is set in Melbourne, Australia. The study will recruit men and women who are living independently—both in supported independent living accommodation and living independently in the community.

To be eligible to participate in the study, participants must satisfy all of the following criteria:

Participants will be unable to participate in the study if they have any significant visual impairment that would prevent reading or performing computer-based tasks requiring color recognition. Additionally, study participants with severe or profound hearing loss will not be eligible to take part in the study. Finally, participants with suspected cognitive impairment (defined as a score ≤24 on the Mini-Mental State Examination [MMSE]) will be excluded.

The primary outcome measure will be changes in cognitive performance as measured by the spatial working memory component of the Swinburne University Computerized Cognitive Assessment Battery (SUCCAB). Reliability and validity assessment has demonstrated that the SUCCAB, especially the spatial working memory component of this battery, is sensitive to aging and intervention and correlates strongly with memory subsets in the Wechsler Adult Intelligence Scale –Fourth Edition [45-47].

Secondary measures include the other SUCCAB cognition measures, social interaction measured using the Berkman-Syme Social Network Index, and depressive symptoms measured using the Geriatric Depression Scale (GDS). Hearing satisfaction (with or without hearing aids) will be measured using the Abbreviated Profile of Hearing Aid Benefit (APHAB) Inventory.

All outcomes will be measured at baseline, after 3 months, and after 6 months (Table 1).

Participant prescreening and assessment will take place at information sessions that will be held at several independent living aged care facilities located in Melbourne and at Swinburne University of Technology. Independent living aged care facilities with existing relationships with Swinburne University of Technology will be chosen. Participants attending information sessions at Swinburne University will be individuals in the community who have expressed interest in assisting with research projects run by the university, and have therefore provided their contact information to be stored in Swinburne’s Centre for Human Psychopharmacology (CHP) database. After providing informed consent, eligible participants will be randomized into 2 equal groups (A and B) for the study, as described in Figure 1.

Allowing for 2.5% significance, 80% power, and a moderate effect size (f=0.25), a power analysis indicated that a repeated measures mixed effects design with 3 repeated measures required a total sample size of 34 participants, split evenly between the 2 groups. This allows for the comparison of changes from baseline to 3 and 6 months for the 2 groups. Except for participants from Swinburne’s CHP database who will need to travel to attend their auditory training sessions at Swinburne University, all other participants will attend their appointments at their facilities. As a result, only a 10% allowance was made for attrition resulting in an overall sample size of 40.

Aged care facility managers will be contacted by telephone to explain the study. If an aged care facility shows interest in the study, researchers will visit the facility to provide the facility manager with more detailed written and oral information. If the facility manager consents for their facility to participate in the study, the study will be advertised at the facility and promotional materials will be distributed to all the residents, inviting them to an information session. Participants from the CHP database will be contacted by the researchers either by telephone or email to explain the study, and participants who express interest will be invited to attend an information session.

At the information session, researchers will explain the purpose and significance of the study. At the same time, a preselection screening will be conducted to identify participants who are willing to wear hearing aids and undergo auditory training to address their hearing loss. Selected participants will be sent a Participant Information and Consent Form package that includes detailed information on the study procedure, a consent form, and a return prepaid envelope. Once written consent is received, participants will be invited to complete baseline measures before enrollment into the study. Recruitment commenced in December 2016.

The following statistical analyses will be performed: