It has now been established that untreated hearing loss is associated with a decrease in cognitive functioning. A longitudinal study performed by Amieva et al. in 2015 found that older adults with untreated hearing loss showed higher rates of cognitive decline compared to older adults of the same age, gender and education level who were fit with hearing aids.
A direct causal relationship between untreated hearing loss and dementia has also been observed. For many years, researchers have theorized that social isolation resulting from untreated hearing loss contributes to the development of dementia but were unable to determine the exact cause.
A study by the Lancet Commissions completed in July of 2017 found that 35% of an individual’s risk for developing dementia later in life is potentially modifiable. They identified 9 modifiable risk factors that make up that 35% and hearing loss was the most significant, at 9%. They confirmed that untreated hearing loss is associated with an increased risk for dementia due to the effects of untreated hearing loss on the brain. They found that when hearing loss is left untreated, this leads to decreased stimulation of the auditory nerve which connects the inner ear to the brain, resulting in decreased stimulation of the auditory cortex of the brain and consequently an increased risk of dementia. Fortunately, they determined that when hearing loss is treated with amplification, the individual’s risk for dementia is comparable to those with normal hearing.