What we’ve found out about hearing loss and cognitive function in children

We recently studied the connection between hearing loss and cognitive function in survivors of pediatric cancer. What we found will change the way we rehabilitate cancer survivors.

Different types of pediatric cancer treatments are ototoxic, or damaging to the ears. As cancer treatments become more effective and survival rates increase, we’re getting a better picture of how various treatments affect patients later on. As a result, our screenings and tests offer insights to treat and mitigate the late effects of cancer treatment.

The connection between hearing impairment and neurocognitive function

Language is learned through exposure to sounds, and hearing is essential for the normal development of speech and language. If sounds are inaudible, especially during infancy and early childhood, basic language skills such as vocabulary, sentence structure and speaking will be delayed or not established. Listening skills influence a child’s ability to read and write and perform other academic skills as well as develop healthy social skills.

Survivors with severe hearing loss are at increased risk for neurocognitive deficits in areas of executive function, processing speed, intelligence and academic function compared to survivors with normal hearing or mild hearing loss. This means the deficits significantly affect survivors’ day-to-day quality of life. Even those with mild hearing loss were at risk for neurocognitive deficits compared to normal hearing survivors, albeit to a lesser degree than survivors with severe hearing loss.

SJLIFE study and long-term health outcomes

Despite advancements in cancer therapy and supportive care, childhood cancer survivors remain at risk for chronic morbidities associated with disease and treatment. The list includes hearing impairment and neurocognitive deficits. This study, to our knowledge, is the first to objectively measure hearing and neurocognitive function in a large cohort of long-term survivors of childhood cancer stratified by treatment exposures.

The SJLIFE study began in 2007 and looks at the long-term impact of cancer treatment in survivors. Our study included SJLIFE participants treated for childhood cancer at St. Jude Children’s Research Hospital who survived five or more years after their original diagnosis and who were eligible for audiologic and neurocognitive testing. We looked at more than 1,500 survivors who completed hearing exams and standard batteries of developmental and age-appropriate neurocognitive tests. The neurocognitive tests were categorized under six main domains, including attention, memory, executive function, processing speed, intelligence and academic function.

Early hearing assessments and interventions

Early detection and intervention of hearing loss in young children result in better outcomes for speech and language development. Interventions typically include hearing aids or cochlear implants, aural rehabilitation, assistive listening devices, and educational services and accommodations. The earlier these interventions occur, the better the outcome.

Studies specifically assessing the association of hearing aid use with neurocognitive function in children with hearing loss are sparse. Studies in older adults with hearing loss who use hearing aids have demonstrated better psychosocial and neurocognitive outcomes compared with those who did not. These studies suggest that earlier intervention with amplification may offset or lessen the association of hearing loss with neurocognitive deficits, social isolation and depression. Presumably, the same would hold true for children and young adults who consistently use amplification.

Additionally, a neuropsychological consultation can identify areas of low performance or areas that may be at risk for future low performance. We can proactively prevent these deficits through additional tutoring or other educational accommodations.

A better understanding of cancer treatment

We also found a few surprises. Study participants were divided into three groups based on the cancer treatment they received. One of the groups was not exposed to cancer treatment known to cause hearing loss, but we found that almost 1 in 5 survivors in this group had severe hearing loss.

Second, hearing aid uptake was surprisingly low among childhood cancer survivors for whom hearing intervention was recommended. Among the 330 survivors with severe hearing loss for whom a hearing aid was recommended, only 75 (22.7%) reported using a hearing aid or cochlear implant. More research is needed to determine if hearing aids can help improve neurocognitive outcomes in childhood cancer survivors, as well as determine barriers to hearing aid adoption and regular use.

Survivors treated with cranial irradiation are at high risk for neurocognitive deficits. But the finding that severe hearing impairment mediates a significant portion of the association between cranial irradiation and neurocognitive deficits is significant. It means childhood cancer survivors treated with cranial irradiation may have fewer late effects if hearing loss interventions are implemented early.