Cochlear Implants and Commercial Motor Vehicle Driver Safety

1. Cochlear Implants and Commercial Motor Vehicle Driver Safety Evidence Report PREPARED FOR: Federal Motor Carrier Safety Administration Medical Review Board Meeting, June 30, 2011 Prepared By: Michelle Tregear, PhD Senior Research Analyst Manila Consulting Group

2. Objective of Evidence Report To examine issues pertaining to the potential impact of cochlear implants (for severe-to-profound hearing loss) on commercial motor vehicle (CMV) driver safety.

3. Background • Cochlear implants • An electronic device implanted in the inner ear for those with severe or profound sensorineural hearing loss (~70 dB thresholds or greater) • Reason this is important to FMCSA • Use of a cochlear implant may enable individuals with severe hearingimpairments to pass FMCSA’s hearing requirements

4. Current Hearing Requirements for CMV Drivers • Hearing requirements per 49 CFR 391.41(b)(11): • Perceive a forced whispered voice, in one ear, at not less than five feet. OR • Have an average hearing loss (as tested by audiometry), in one ear, less than or equal to 40 decibels (dB).

5. Hearing – CMV Drivers • Why is functional hearing important for driving? • Hear warning sounds that may allow the driver to react to a potential hazard before it is visible • Detect problems with a vehicle • To facilitate communication between the driver and others (e.g., dispatchers, loading dock personnel, passengers, and law enforcement officers).

6. Background • Preliminary questions we asked: • Background statistics on hearing loss • What are the different types of cochlear implants, and what types of hearing loss are they used to treat? • What are the criteria and/or indications for a cochlear implant? • What are the epidemiological factors associated with cochlear implantation? (e.g., prevalence)

7. Targeted Evidence Search • Key Questions: • How effective are cochlear implants (e.g., is auditory function following cochlear implantation restored to a level that would permit safe driving as established by existing Federal standards for hearing?) • What is the nature of hearing capability following cochlear implantation (e.g., sound localization), and are there associated factors that may not be conducive with safe driving? • Are there any other factors associated with cochlear implantation that may increase crash risk (e.g., disrupted vestibular function)?

8. Background - Hearing Loss The sixth-leading chronic disabilityin the United States Primary cause: age-related; ≥50% of all hearing loss occurring over age 65 Approximately 36 million American adults suffer from hearing loss Men more likely to be deaf or have hearing loss (4.3% and 2.4%) Sensorineural hearing loss is the most common form (~90% of all hearing losses); Conductive hearing loss (<10%)

9. Background - Devices ** For design improvements and labeling changes

10. Background – Indications for Cochlear Implants • Indications have evolved over time • Previously – only postlingually deafened adults (0% accuracy on monosyllabic word test); profoundly deaf • Currently – adults and infants, both pre- or postlingually deafened (50% or less accuracy on word test; 60% or less on open-set sentence recognition); severe-to-profound hearing loss (~70 dB)

11. Background - Epidemiological Factors • Who receives the device? • Children and adults with binaural sensorineural hearing loss • How widespread is their use? • Worldwide, about 60,000 cochlear implants have been placed during the past 20 years, approximately one half of them in adults • Data vary as to how many individuals in the U.S. are potential candidates for receiving cochlear implants. These figures range from 250,000 to 1 million people • What are the current trends of cochlear implant devices? • Primarily unilateral, but growing use of bilateral implantation

12. Key Questions • Key Question 1: • How effective are cochlear implants, and is auditory function following cochlear implantation restored to a level that would permit safe driving as established by existing Federal standards for hearing?

13. Key Question 1: Cochlear Implant Efficacy and Functionality • Information limited to single systematic evidence review • Bond et al. (2009) compared hearing ability in individuals with: • Unilateral CI vs. no assistive hearing device • Unilateral CI vs. hearing aids • Bilateral CI vs. unilateral CI • Pre- and post-implant measures (subjects acted as own control) • Outcomes considered: • Speech perception • Quality of life • Sensitivity to sound

14. Key Question 1: Bond et al. (2009)Unilateral CI vs. no assistive device • 4 studies; n=948 patients total; primary outcome: speech perception • Tested both before and 3-18 months after surgery • All studies reported improvements in speech perception measures following cochlear implantation compared to pre implant measures with no assistive device (see handout #1)

15. Key Question 1: Bond et al. (2009)Unilateral CI vs. hearing aid • 4 studies; n = 248 patients total; primary outcome: speech perception; also speech production, localization, quality of life • Tested both before and 6-12 months after surgery • All studies reported improvements in speech perception measures following cochlear implantation compared to pre implant measures with hearing aid • Improved sound production (one study) • Improved quality of life (one study) • No benefit for sound localization (one study) (see handout #2)

16. Key Question 1: Bond et al. (2009)Bilateral CI vs. unilateral CI • 4 studies; n = 127 patients total; primary outcome: speech perception, sound localization, and quality of life • Note: Sound localization addressed in key question 2 • Speech perception was found to be improved in quite and in noisy conditions • In some studies the speech perception benefit was either borderline or not significant (see handout #3)

17. Key Question 1: Summary of Results • Evidence indicated that, compared with non-technological support, cochlear implants appear to lead to improvements in functional hearing, ability to understand speech and improve quality of life • Improvements most strongly associated with duration of pre-implantation deafness and age at implantation • Bilateral implants appear to be associated with improvements in hearing in noisy situations and understanding speech • In all studies, there was wide individual variation in improvement

18. Key Question 2: Cochlear Implant and Sound Localization • 5 studies and 1 systematic review of 29 studies • Relevant comparisons: • Sound localization with unilateral CI (alone or bimodal) • Sound localization with bilateral CI • Outcome assessed: • Sound localization

19. Key Question 2: Sound LocalizationSummary of Evidence • Unilateral CI recipients: poor sound localization ability (performance close to chance) • Bilateral CIs and/or bimodal stimulation demonstrated varying degrees of significant improvement compared to unilateral CI recipients or contralateral ear hearing aid • Bilateral implants conferred up to 30 degrees improvement in localization acuity over unilateral use • Best performing bilateral implant achieved accuracy of 4.4 degrees sound-source discrimination (normal hearing performance (1.7 degrees).

20. Sound Localization and CMV Drivers • There is no data available to address question of whether or not sound localization capability following cochlear implantation is restored to a level sufficient for driver safety • Current medical fitness standards for commercial drivers do not include sound localization requirements • In individuals normal hearing, sound localization is accounted for by binaural cues requiring hearing function in both ears • Current requirements for CMV drivers do not require hearing in both ears • The importance of sound localization ability for drivers is unclear

21. Key Question 3: Vestibular dysfunction • Search found 11 studies • Measured vestibular function pre- and post-implantation • 697 patients • Measures of vestibular function included both: • Subjective measures • Dizziness Handicap Inventory (DHI) • Activities-specific Balance Confidence (ABC) scale • Objective measures • Eye-tracking tests • Optokineticnystagmus

22. Key Question 3: Vestibular dysfunction Vestibular impairment is a common condition among those who have hearing loss (prior to CI; range 26% to 58%) Cochlear implantation may result in temporary vestibular disruption (range 29% to 76% patients). The number of those who receive CIs and suffer from severe vestibular symptoms long-term is relatively low. Some studies reported severe dizziness or vertigo in subjects following CI: most patients recovered with vestibular rehabilitation

23. Cochlear Implantation: Conclusions No literature was identified that looked at outcomes in commercial drivers or in individuals in other safety sensitive occupations. Primary outcomes considered included speech perception, sound localization, and adverse consequences, such as vestibular disruption following cochlear implantation. Cochlear implantation improves hearing performance and speech perception, although not to the degree of people with normal hearing; the degree of improvement varies for each recipient, depending on factors such as the duration of deafness, whether or not the individual was pre- or postlingually deafened, and age at implantation.

24. Cochlear Implantation: Conclusions • Bilateral cochlear implantation is an advantage over unilateral cochlear implantation in speech perception in noise and sound localization tasks. • Most individuals have a unilateral cochlear implant • Current trends outfit patients with two cochlear implants or cochlear implant/hearing aid combination to improve outcomes • A large number of hearing-impaired individuals suffer from preoperative vestibular symptoms • Between 20% and 76% of cochlear implant recipients exhibited vestibular impairment following cochlear implantation • Individuals with prolonged symptoms usually receive vestibular rehabilitation.