Unfortunately there is growing evidence that hearing loss may increase the risk of cognitive problems. In a recent study published in a well regarded medical journal the authors evaluated the cognitive and hearing levels of 1,984 older adults. They compared those with normal hearing to those with hearing loss. Those with hearing loss had lower scores on baseline cognitive testing and were more likely to have significant impairment after six years, The authors also found that the worse the hearing, the worse the mental decline.
The take away message is that there is good reason to treat hearing loss. If doing so even slightly heads off dementia it would be a big plus.