Preference and Outcomes for Fast Versus Slow Compression in Hearing Aids for Older Adults: A Randomized Control Trial

To determine whether normally aging older adults, fitted with hearing aids, report a benefit from, or a preference for, slow or fast-acting compression, and whether this relationship is influenced by cognitive ability, hearing loss, or previous experience with hearing aids.

A single-blinded, crossover randomized control trial. Fifty-six participants were recruited from the population attending a UK National Health Service (NHS) hearing assessment clinic, both new and experienced hearing aid users. Participants were aged 56 to 85 years, with symmetrical mild-to-moderate hearing loss. Participants trialed hearing aids for 2 months in each of two settings, slow or fast-acting compression. Speech recognition in quiet and in noise were measured, unaided and aided after fitting with each compression setting. A battery of cognitive tests, self-reported hearing aid outcomes and the participant's preference for the first or second fitting were also collected at the end of the trial.

Seventy-seven percent of participants stated a preference for one of the compression speed settings. A roughly equal number of participants preferred fast or slow-acting compression. Hearing thresholds were the only predictive factor for compression speed preference: the larger the hearing loss, the more likely it was that patients preferred a slower compression speed. Neither cognitive scores nor the degree of experience with hearing aids predicted the preference for either compression speed. Objective benefit, measured by speech understanding in quiet and in noise, was not affected by compression speed.

Participants with a greater degree of hearing loss tended to prefer slow-acting compression. The optimum boundary between the preference for "fast" versus "slow" compression speed was a four-frequency average hearing threshold of 35 dB HL in the better ear. When the default compression speed was set to "fast" for those with an average hearing threshold below 35 dB HL, and to "slow" for those with a greater degree of hearing loss, this setting correctly reflected a user's preference in about four in five cases. Neither compression speed offered a significant benefit for speech recognition in noise and quiet. Likewise, neither cognitive performance nor previous experience with hearing aids predicted the amount of reported benefit or preference. Limitations to the study included a positive association between hearing threshold and experience with hearing aids. The study also demonstrated a strong association between the preference and the order of compression speed provided, with users tending to prefer the second fitting.