Having a conversation in a noisy restaurant can be difficult. For many elderly adults, it's often impossible. But with a little practice, the brain can learn to hear above the din, a new study suggests.
Age-related hearing loss can involve multiple components, such as the disappearance of sensory cells in the inner ear. But scientists say that part of the problem may stem from our brains. As we get older, our brains slow down—a natural part of aging called neural slowing. One side effect of this sluggishness is the inability to process the fast-moving parts of speech, particularly consonants at the beginning of words that sound alike, such as "b," "p," "g," and "d." Add background noise to the mix and "bad" may sound like "dad," says Nina Kraus, director of the Auditory Neuroscience Laboratory at Northwestern University in Evanston, Illinois. "Neural slowing especially affects our ability to hear in a noisy background because the sounds we need to hear are acoustically less salient and because noise also taxes our ability to remember what we hear."
Building on animal studies that pointed to an increase in neural speed following auditory training, Kraus and colleagues enrolled 67 people aged 55 to 70 years old with no hearing loss or dementia in an experiment. Half the group completed about 2 months of exercises with Brain Fitness, a commercially available auditory training program by Posit Science. (The team has no connection to the company.) The exercises helped participants better identify different speech sounds and distinguish between similar-sounding syllables, such as "ba" or "ta."
They would listen to words and sentences—all with varying levels of background noise—and had to repeat back what they heard.
All participants completed a series of tests at the outset of the study to measure short-term memory, brain processing speed, and the ability to hear and understand speech in a noisy environment. Researchers also recorded brain activity to measure how quickly the brain registered hearing the syllable "da" over background noise. After 40 hours over 8 weeks, those in the training group showed improvement across the board, the team reports online this week in the Proceedings of the National Academy of Sciences.
"After training, the participants' neural timing did not become equivalent to that of a young adult," Kraus says, "but they were, however, able to successfully hear, remember, and understand sentences in noisy background listening conditions—conditions that prior to training, rendered understanding of what had been said impossible." When participants repeated behavioral and electrophysiological tests post training, they understood about 20% more words and could process about 15% more items on a timed test and showed a 50% increase in neural timing. Those in the nontraining group showed no improvements in any area.
"The behavioral measures give you perspective on whether a treatment could actually work in helping improve the communicative abilities of older adults, while biological or auditory electrophysiology measures give you an indication of the actual mechanistic pathways that the training may be affecting," says Frank Lin, an otolaryngologist at Johns Hopkins University in Baltimore, Maryland, who was not involved in the study.
The findings are important, Lin adds, given recent research that points to a link between hearing loss in the elderly and age-related dementia. "We currently think that peripheral, age-related hearing loss could contribute to cognitive decline and dementia through two mechanistic pathways—social isolation and cognitive load," he says. "This study is tremendously important given the aging of the population and our need to identify novel and effective interventions to reduce age-related cognitive and functional declines in older adults."
Kraus's team is now investigating how long the benefits of training last and whether the program will be as effective in people with minor to severe age-related hearing loss or dementia.