Aug 2020 The Hearing Journal
Factors affecting cochlear implant (CI) users’ postoperative performance, such as age at implantation, duration of deafness, and spiral ganglion cell count, are outside of clinicians’ control and cannot be easily modified or modified at all. Researchers have recently identified one potentially important and malleable factor that audiologists have influence over and can use to optimise speech recognition outcomes for CI users: the average number of hours of processor use per day.
This concept is not new when it comes to children with CIs: The positive correlation between consistent CI use and high speech recognition scores is well established in the paediatric population. But evidence that this may also be true for adult CI recipients has only recently come to light - that the average number of hours of device use per day, not the average number of hours listening to speech in noise, is correlated with postoperative performance.
Jourdan T. Holder, AuD, a cochlear implant audiologist and PhD candidate at the Vanderbilt Bill Wilkerson Center, decided to conduct her own study because she observed a similar trend among her patients. “Cochlear implant recipients who had higher speech recognition scores tended to wear their cochlear implant processor more often,” she said. “I was interested to see if this trend persisted in a larger sample.”
Holder and her colleagues conducted correlation analyses for CI-aided speech recognition, including consonant-nucleus-consonant monosyllables and AzBio sentences, and average hours of processor use per day for 300 adult CI users. Holder’s study also yielded a stronger correlation of 0.61. To put the significance of the study result into context, a correlation of 0.6 is stronger than correlations between speech recognition outcomes and other commonly referenced factors such as age at implantation, duration of deafness, and electrode position, and is generally equivalent to correlations between speech recognition and spectral resolution, and spectrotemporal resolution, said Holder. “When studying cochlear implant outcomes, it is rare to see one variable correlate so strongly with speech recognition outcomes in a large sample size of 300 patients,” she said.
The primary importance of this strong correlation lies in the potential malleability of daily cochlear implant use. “Unlike duration of deafness, age at implantation, and electrode position, daily cochlear implant use may be able to be manipulated following implantation to yield improvement in speech recognition outcomes,” Holder said.
The implication of the results of Holder's study extends beyond improving outcomes for individual CI users, however. “Audiologists recommend that patients wear their cochlear implant processors ‘all day’ or ‘all waking hours,’ but we currently lack a data-driven recommendation regarding how many hours per day a patient should wear their processor for optimal performance,” said Holder. “Our work and others show that there is tremendous variability in the number of hours per day that recipients wear their cochlear implant processor, suggesting that the current recommendation may be ambiguous. This study offers a first step toward a data-driven recommendation for daily use, and suggests that higher speech recognition scores may be associated with more consistent processor use.”
Holder's study offers audiologists a good rule of thumb for the average number of hours for CI use per day they should recommend to help optimise patients’ speech recognition outcomes. “Our data suggest that 10.2 hours of processor use per day is associated with average (50%) speech recognition performance,” Holder said. “Greater than 10 hours of daily processor use is associated with above-average speech recognition and lower variability in outcomes for all measures. For example, the participants in our group wearing their processor about 10 hours per day ranged in performance from 24 to 82 percent correct for CNC word recognition, whereas participants wearing their processor 15 hours per day ranged from 40 to 92 percent correct on the same measure. “
Audiologists’ current recommendation of full-time use or all waking hours may be ambiguous for some users, Holder said. “Although this study does not assess causation, it is reasonable for clinicians to use 10 hours of cochlear implant use per day as a minimum recommendation, as 10 hours was associated with average performance,” she said. “Our correlational data suggest that greater than 10 hours of cochlear implant use per day is associated with higher performance, so clinicians may wish to implement higher daily use goals to improve speech recognition performance as we continue to investigate the causal link between these two measures.”