Up to 360 million people worldwide have impaired hearing, according to the World Health Organization and nearly 45 million people have Alzheimer’s or another form of dementia, according to Alzheimer’s Disease International.

Many scientists have seen these age-related maladies as unrelated. Recent research, though, has raised the possibility that untreated hearing loss may lead to or exacerbate cognitive impairment. “This area of research is wide open and the potential impact is huge,” says Frank Lin, an associate professor of otolaryngology-head & neck surgery, geriatric medicine, mental health, and epidemiology at the Johns Hopkins University School of Medicine. “If hearing loss affects brain function, treating it could turn out to be a powerful way to address age-related cognitive issues.”

In 2013, Lin published a study in the Journal of the American Medical Association, showing that older adults with hearing loss were at greater risk for problems with thinking and memory than were people of the same age who had normal hearing. In the study, Lin found that the cognitive abilities of participants with hearing loss declined up to 40% faster than other participants.

A few theories as to why have gained ground in recent years. First is the idea that hearing loss imposes an extra, detrimental workload on the brain. Another theory is that hearing loss may cause parts of the brain to atrophy. In a study published in 2014 in the journal NeuroImage, Lin and his associates found that people who have been diagnosed with hearing loss for at least seven years were more likely to have brains with smaller lateral temporal lobes, which are involved with retaining visual memories, processing and deriving meaning from sensory input, and storing new memories.

-Content by The DANA Foundation