From a New York Times online article:
…the researchers demonstrated that the biggest drop in cognitive ability occurs at the slightest level of hearing loss — a decline from zero to the “normal” level of 25 decibels, with smaller cognitive losses occurring when hearing deficits rise from 25 to 50 decibels.
Hearing loss is now known to be the largest modifiable risk factor for developing dementia, exceeding that of smoking, high blood pressure, lack of exercise and social isolation, according to an international analysis published in The Lancet in 2017.
the new findings on cognitive losses linked to subclinical hearing loss, gleaned from among 6,451 people age 50 or older, suggest that any degree of hearing loss can take a toll.
Boomers Daily 