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Hearing loss may predict Alzheimer's disease, according to a new study.

The brain becomes smaller with age. However, new research reveals that brain tissue loss seems to be fast-tracked in older adults with hearing loss. 

The latest study used data from the ongoing Baltimore Longitudinal Study of Aging, which was started in 1958 by the National Institute on Aging to monitor various health factors in thousands of men and women.

Lead researcher Frank Lin looked at 126 participants who underwent yearly MRI scans for up to 10 years. Researchers said that the beginning of the study, 75 had normal hearing and 51 had impaired hearing, with at least a 25-decibel loss.

After comparing brain scans of participants, Lin found that participants whose hearing was already impaired at the start of the study had faster rates of brain shrinkage compared to those with normal hearing.

The study found that participants with impaired hearing lost more than an additional cubic centimeter of brain tissue each year compared with those with normal hearing. However, participants with impaired hearing also had significantly more shrinkage in some brain regions like the superior, middle and inferior temporal gyri, brain structures responsible for processing sound and speech.

The shrinkage in brain structures responsible for sound and speech isn't a surprise as loss of brain tissue in those areas might simple by a consequence of lack of stimulation. However, other brain regions that work with structures that process sound and speech such as the middle and inferior temporal gyri, are also affected.  This is worrying because these structures play important roles in memory and sensory integration and have been linked to mild cognitive impairment and Alzheimer's disease.

"Our results suggest that hearing loss could be another 'hit' on the brain in many ways," Lin said.

Researchers said the findings suggest that treating hearing loss is very important.

"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," Lin explained.

The findings are published in the journal Neuroimage.