13 February 2018
Companion papers detailing a multicenter double-blind randomized placebo-controlled trial investigating the effects of hearing aids (HA) on cognitive and functional outcomes for persons with Alzheimer's disease (AD) were recently published in the Journal of Alzheimer's Disease [1,2]. While there is ample evidence of comorbid cognitive and sensory decline as well as increased risk of dementia for persons with age-related hearing loss (ARHL), there has been very little research as to the effects of treatment of hearing loss for persons with Alzheimer's disease and related dementias (ADRD). It is commendable to undertake the challenge of implementing a double-blind randomized placebo-controlled trial. Such a trial would have the potential to provide definitive evidence regarding the efficacy of treating hearing loss as a key component of providing care for persons with ADRD.
Although the authors describe the treatment in the study as "hearing aids", the treatment for hearing loss, in fact, is restoring audibility, which is typically achieved through evidence-based fit hearing aids. Given that returning audibility is the treatment proposed in this study, one would expect a protocol to have been used in order to ensure that audibility was achieved for participants. At a minimum, one would expect data to be reported related to what level of audibility was returned to individuals which would have come in the form of measuring the output of the hearing aids in the individual's ear canal and reporting the speech intelligibility index achieved for various input levels (especially soft and moderate input levels). These data would be essential in interpreting the results of this study.
The authors indicate that "the gain rule used for amplification was based on a proprietary fitting algorithm (Adaptive Phonak Digital), derived from the National Acoustic Laboratories' nonlinear fitting method version 1." As Sanders et al.  revealed in their article entitled "Manufacturer's NAL-NL2 fitting fail real-ear verification", the method used in this study actually ensures a lack of increased audibility for soft and moderate inputs. In fact, the NALNL1 proprietary fitting version used by the authors is even poorer in terms of audibility than NAL-NL2 investigated by Sanders et al. . This alone would predict the finding of no difference between the placebo (actually mild gain) and hearing aid (also mild gain due to underfitting created by this proprietary fitting algorithm) conditions used in this study.
The authors state that "it seemed important to conduct a rigorous interventional study to investigate potential benefits in terms of psychological symptoms, of auditory rehabilitation of elderly patients suffering both ARHL and AD". A rigorous interventional study would have required an evidence-based approach to fitting and verifying the audibility provided by the amplification used in the study, and this was not accomplished. The study reports essentially no difference between the group with hearing aids and the placebo control group (mild gain amplification) on cognitive status, functional abilities, or behavioral symptoms. Given the essential lack of audibility difference in the hearing aid and placebo condition due to the hearing aid fitting protocol, this null finding is to be expected.
The authors also used self-reported or care-giver reported use data in their analysis. Taubman et al.  among others have reported that individuals are not accurate in reporting use time by the day or week, both over and underestimating usage. The investigators used hearing aids that include a data logging feature that could have provided them with accurate use data given the number of visits that were included in the study. It is impossible to know if individuals who never or rarely wore their hearing aids were included in this analysis because the analysis relied on self-report.
If the authors are able to continue this work, we hope they will employ best practices when fitting and verifying hearing aids so this important work can be interpreted in light of a known treatment (audibility and hours of use) that has been applied as compared to a true placebo.
The authors acknowledged in the discussion that comprehensive aural rehabilitation was not included in the protocol and that this may have impacted the results. We agree that informational counseling, device use, and communication training may be essential to the success of this group of patients. However, no amount of counseling will make up for an inadequately fit hearing aid. This type of investigation must first ensure that an audible signal is being returned to the patient and then appropriate aural rehabilitation can be expected to have the greatest impact.
Finally, with regards to the primary outcome measure, the authors set a 'success' criterion of < 6 points of decline on the Alzheimer's disease Assessment Scale Cognitive Subscale (ADAS-Cog). This value was based on the expected decline of cognitive scores per the literature on ADAS-Cog in an AD population; however, both the active HA group and the placebo group performed better than this expected decline. This may be explained by both of these groups essentially having very mild gain hearing aids, which may have provided some minimal benefit but no difference between the group because of the fitting issues discussed above.
In summary, the findings from these papers should not deter families or providers from seeking to identify and treat ARHL in persons with ADRD. The potential benefit of HA treatment will come from an evidence-based HA fitting procedure that ensures that audibility is returned to the individual followed by an aural rehabilitation program that assists the patient and family/caregivers in understanding communication strategies and the reality of adjustment to routinely using amplification.
Sara K. Mamo1 and Catherine V. Palmer2, 3,4
1Department of Communication Disorders, University of Massachusetts Amherst
2Department of Communication Science and Disorders, University of Pittsburgh
3Department of Otolaryngology, University of Pittsburgh
4University of Pittsburgh Medical Center (UPMC)
 Adrait A, Perrot X, Nguyen MF, Gueugnon M, Petitot C, Collet L, Roux A, Bonnefoy M; ADPHA study group (2017) Do hearing aids influence behavioral and psychological symptoms of dementia and quality of life in hearing impaired Alzheimer's disease patients and their caregivers. J Alzheimers Dis 58, 109-121.
 Nguyen MF, Bonnefoy M, Adrait A, Gueugnon M, Petitot C, Collet L, Roux A, Perrot X; ADPHA study group (2017) Efficacy of hearing aids on the cognitive status of patients with Alzheimer's disease and hearing loss: A multicenter controlled randomized trial. J Alzheimers Dis 58, 123-137.
 Sanders J, Stoody T, Weber J, Mueller HG (2015) Manufacturers' NAL-NL2 fittings fail real-ear verification. Hear Rev 21, 24.
 Taubman L, Palmer C, Durrant J, Pratt S (1999) Accuracy of hearing aid use time as reported by experienced hearing aid wearers. Ear Hear 20, 299-305.