Procedures and intervention
During the first visit, a clinical history was taken. Also, the Montreal Cognitive Assessment (MoCA) was applied [29,30] to guarantee no previous cognitive impairment (based on normative scores for hearing-impaired individuals [31]) and to exclude those individuals who could possibly introduce bias into the results of the proposed intervention. Hearing aids (receptor-in-the-ear, RIE) were then fitted according to the previously performed randomization. The acoustic gain prescription and the algorithms activated are described in Figure 1. After the first fitting, microphone probe measurements were made so as to ensure that both Groups A and B received at least 50% Speech Intelligibility Index (SII) in speech mapping for weak intensity sounds and at least 80% SII for medium-to-strong sounds. We activated the premium and basic features as shown in Figure 1. Checks were also carried out in Group C to ensure that the non-amplifying hearing-aid (placebo) did not exacerbate auditory deprivation of these control subjects. All participants were instructed on the use of the hearing aids and were given the contact of the researchers to remedy any problems arising during the use of the devices. After fitting the hearing aids, part of the Brief Neuropsychological Assessment Instrument was applied (NEUPSILIN) [32] to assess attention and memory abilities (for further details on this neuropsychological test, please read Fonseca et al., 2008 [33]). The patients we studied in this protocol did not pay for any device or health service as it happens in our health service which is financed by the Brazilian Public Health System (named SUS).
At the end of the consultation, cortical auditory responses were determined using a HEARLabĀ® device according to the protocol recommended by Durante et al. [34] with speech stimuli (/m/, /g/ and /t/ at intensities of 55, 65 and 75 dB). Only latencies of P1 and N1 waves were employed. At the end of that visit, the next visit was scheduled (12 weeks later). During the period between the visits, the researchers contacted the patients every two weeks to ensure that hearing aids were being used properly.
Twelve weeks after the first visit, the participants returned to the service and were reassessed using the same NEUPSILIN tasks. Cortical auditory responses were measured again with the HEARLabĀ® device according to the previously applied protocol. At the end of that visit, participants completed the International Outcome Inventory for Hearing Aids (IOI-HA), which investigated self-perceived usage, benefit, residual activity limitation, overall satisfaction, residual participation restriction, residual impact on others and quality of life change [35].