Researchers at Dartmouth’s Geisel School of Medicine, in collaboration with investigators at the McGill University affiliated Douglas Research Center, Northwestern University, and Creare, LLC, have received a $6 million grant from the National Institute on Aging to study the relationship between auditory function and Alzheimer’s disease.

“Hearing loss has been considered a risk factor for Alzheimer’s disease, but the underlying mechanism has remained elusive,” says Jay Buckey Jr., MD, a professor of medicine at Geisel and co-principal investigator on the grant project along with Pedro Rosa-Neto, MD, PhD, of the Douglas Research Institute and McGill.

Hearing depends on two key elements, the ear and the brain. This two-part hearing process is complex and interdependent, Buckey explains. “One part involves taking a sound (acoustic signal) and turning it into nerve signals, and that’s what the ear does. The other part of the hearing system is taking those nerve signals and making sense out of the sound. That’s what your brain does.”

Alzheimer’s disease is the leading cause of dementia and is defined by the presence of cerebral amyloid plaques and tau neurofibrillary tangles in the brain. If hearing loss worsens Alzheimer’s disease, these plagues and tangles would develop faster and interventions, like hearing aids, might slow or prevent progression towards dementia.

On the other hand, the hearing complaints for Alzheimer’s patients may originate in the brain from these plaques and tangles, which means hearing aids may not help with cognition.

“What we’re wondering is, is this relationship between hearing and Alzheimer’s a ‘bottom up’ process, meaning problems with the ear lead to the progression of Alzheimer’s, or is it more of a ‘top-down’ process where the Alzheimer’s effect on the brain is influencing hearing ability?”

To make that determination, the investigators will conduct a longitudinal study, comparing imaging of amyloid plagues and tau tangles and biomarker test results of 70 older adults with mild cognitive impairment (i.e., a precursor to Alzheimer’s disease) to those of a group of other adults that are cognitively unimpaired and a group of young, healthy adults.

“We’ll be working with colleagues in Montreal who are expert in tau and amyloid PET imaging,” says Christopher Niemczak, PhD, a senior scientist in the Buckey Lab (the Space Medicine Innovations Lab), an assistant professor of medicine at Geisel, and co-investigator of the grant project team.

This will allow the team to follow study participants and look at the rate of progression of these amyloid and tau proteins in their brains across three time points over a five-year period. “The Montreal team will also be collecting cerebrospinal fluid, blood samples, and performing neurocognitive testing,” says Niemczak. “Meanwhile, we’ll be teaming up with colleagues at Northwestern and Creare, LLC to perform a battery of different hearing tests that will help us assess auditory function in the participants.”

“We hope the results will show the role that both the ear and the brain play in hearing loss associated with Alzheimer’s disease,” says Buckey. “The results may also show if tests of hearing ability may be useful for predicting Alzheimer’s disease or tracking its progression.”

Article appeared on Dartmouth Geisel School of Medicine