It is well known by audiologists that people with uncorrected hearing loss lose their ability to understand speech and do not regain it once it is gone. Results of a study recently published (Neuroimage, Jan, 2014) by Frank Lin, MD, PhD of Johns Hopkins University appears to explain why this happens.
As we age, our brain shrinks in size and this appears to result in memory loss, falling and other factors associated with "senioritis". Dr Lin has found that this shrinkage occurs much faster in people with hearing loss.
Using information from the Baltimore Longitudinal Study of Aging, Dr Lin compared brain changes in people with hearing loss and people with normal hearing. The study involved 126 participants between 56 and 86 years of age who received annual MRIs and a complete physical (including hearing tests) for up to 10 years. He found that "those participants whose hearing was already impaired at the start of the sub-study had accelerated rates of brain atrophy compared to those with normal hearing".
Most of the brain loss occurred in the areas that process sound and speech, as would be expected. Because of hearing loss, there is less neural input to the brain, resulting in a lack of stimulation to the areas that manage sound. Just as your muscles will weaken and become reduced in size through lack of use, the brain needs input in order to maintain its function.
The permanent lack of understanding speech is enough cause for concern, but Dr Lin adds the caution that areas of the brain do not work alone. The areas where he found atrophy are also important for "memory and sensory integration and have been shown to be involved in the early stages of mild cognitive impairment and Alzheimer's disease".
The important message from this study is that hearing loss may be a cause of, or at least be responsible for accelerating, loss of mental function associated with aging. According to Dr Lin, "If you want to address hearing loss well, you want to do it sooner rather than later. If hearing loss is potentially contributing to these differences we're seeing on MRI, you want to treat it before these brain structural changes take place".
The American Speech and Hearing Association recommends that everyone should have their hearing checked by their 50th birthday. Even though you may not notice any trouble hearing, this will provide a baseline for comparison with future tests. Dr Lin's research has indicated that the sooner a hearing problem is discovered and corrected, the more likely it will be that some of the negative effects of aging may be avoided.