Senior study investigator and Johns Hopkins otologist and epidemiologist Dr. Frank Lin said all study participants had normal brain function when the study began in 2001. They were initially tested for hearing loss, defined as recognizing only those sounds louder than 25 decibels.
The data on a subset of 1,984 men and women ages of 75-84 came from a larger, ongoing study monitoring the health of older blacks and whites in Memphis and Pittsburgh.
The volunteers with hearing loss had repeated cognition tests over six years.
The study found those who had hearing loss also had cognitive abilities that declined some 30 percent to 40 percent faster than those whose hearing was normal.
Levels of declining brain function were directly related to the amount of hearing loss, the researchers said.
The findings, published in the journal Internal Medicine, found on average, older adults with hearing loss developed a significant impairment in their cognitive abilities 3.2 years sooner than those with normal hearing.