Cognitive Functioning Improves After Cochlear Implant

Cognitive functioning improved 12 months after cochlear implantation for older adults with severe hearing loss and poor cognition, data from a single-center study showed.

Among 21 cochlear implant candidates whose preoperative scores indicated mild cognitive impairment, overall cognitive scores improved 12 months after cochlear implant activation from a median percentile of 5 to 12 (difference of 7, 95% CI 2-12), reported Ellen Andries, MSc, of Antwerp University Hospital in Belgium, and colleagues.

Eight participants’ scores improved enough to move them out of the mild cognitive impairment category (16th percentile), Andries and co-authors reported in JAMA Otolaryngology-Head & Neck Surgery.

Speech recognition in noise improved, which was tied to a rise in cognitive abilities.

The study is one of the first to examine cochlear implants among older adults with preoperative poor cognitive functioning, the researchers noted.

“Several large studies have previously demonstrated an improvement of cognitive functioning in severely hearing-impaired older adults after cochlear implantation, but few of these studies specifically analyzed participants achieving poor cognitive outcomes preoperatively,” Andries told MedPage Today.

The findings suggest cochlear implantation is not contraindicated in candidates with cognitive decline and should be considered after a multidisciplinary evaluation, she noted.

“The management of modifiable risk factors for dementia, such as hearing loss, is important as there is currently no cure for dementia and its incidence is rising rapidly,” Andries added. The top modifiable risk factor for dementia prevention is hearing loss, which accounts for 8.2% of the global dementia burden, according to a recent Lancet Commission report.

The analysis included cochlear implant candidates 55 and older with poor baseline cognitive scores among participants in Antwerp University Hospital’s larger prospective cohort study from April 2015 to September 2021. Median age was 72, and 62% were men. Speech processors were activated approximately 4 weeks after cochlear implantation surgery.

All participants had a preoperative total score on the Repeatable Battery for the Assessment of Neuropsychological Status for hearing-impaired patients (RBANS-H) that indicated mild cognitive impairment — a score at least 1 standard deviation below the mean compared with age-appropriate normative data (16th percentile or lower).

The RBANS-H evaluates five cognitive subdomains: immediate memory, attention, language, visuospatial/constructional, and delayed memory. The test battery has alternate forms A and B; both were used to assess patients 1 month preoperatively and 12 months after speech processor activation.

Speech recognition in noise was measured with the Leuven Intelligibility Sentences Test (LIST). Anxiety and depression symptoms were identified using the Hospital Anxiety and Depression Scale (HADS) preoperatively and 12 months after activation.

Most participants (16 of 21) showed improvement in the RBANS-H total percentile 12 months after cochlear implant activation. The RBANS-H percentile remained stable in one participant and decreased in four.

Speech recognition in noise improved after activation (mean score 17.16 vs 5.67 on a scale where lower is better, for a difference of −11.49, 95% CI −14.26 to −8.72). Better speech recognition in noise was associated with significantly better cognitive functioning (r_s −0.48).

Other variables, including years of education, sex, RBANS-H version, and depression and anxiety symptoms, were not related to changes in RBANS-H scores.

The findings support the information degradation hypothesis as a potential explanation for the link between hearing loss and cognition, Andries and colleagues observed. “This hypothesis states that older adults with hearing loss need to rely more on cognitive resources to compensate for impaired auditory input, resulting in more mental fatigue and a higher cognitive load, which leads to a reduction of cognitive resources available for other cognitive tasks,” they noted.

The study lacked a control group for ethical reasons, the researchers pointed out, and unknown factors like infection, medications, or pain could have influenced cognitive performance.

The small sample size was also a limitation, they acknowledged. “Further longitudinal research including a larger sample of cochlear implant candidates with cognitive decline is therefore recommended,” they wrote.