While earlier studies have shown that hearing loss causes structural changes to the areas of the brain associated with auditory processing, it was unknown whether these changes occurred before or after the hearing loss.
Using information from the ongoing Baltimore Longitudinal Study of Aging, researchers from Johns Hopkins Medicine tracked brain changes in 126 participants over ten years. Each participant completed a physical examination, including a hearing test. At the start of the study, 75 had normal hearing and 51 had impaired hearing.
After analyzing MRI scans taken over the years, researchers found that participants with impaired hearing had accelerated brain atrophy compared to those with normal hearing. They also showed increased shrinkage in certain ares of the brain, such as superior, middle and inferior temporal gyri, structures involved with auditory processing.
The results of the study have been published in the journal NeuroImage.
Shrinkage in these regions of the brain is expected because of the lack of auditory information flowing through it, but these areas are responsible for more the just sorting out sounds and language. They also play roles in memory and sensory integration, involved in early stages of mild cognitive impairment and Alzheimer's.