Older people have trouble understanding speech, even if their hearing is fine. That’s one of the conclusions of a new study by the Research Group Experimental Oto-rhino-laryngology (ExpORL) of KU Leuven. The results underline the importance of tests to measure if people with seemingly normal hearing have really understood a message.
It’s common knowledge that older people are more likely to have hearing problems, making it more difficult for them to understand others. But even people whose hearing is good can experience issues with this: they can hear sound, but don’t understand the message. "That’s why we wanted to see what happens in the brain in these cases," says PhD student Lien Decruy.
The team led by Professor Tom Francart had 54 participants between 17 and 82 years old with normal hearing listen to sentences and stories. To find out if the participants were able to understand the speech properly, the researchers used a new method that allows parts of the offered speech to be decoded from the brain activity. The effect of background noise on speech understanding was measured by adding different types of interference, such as static noise or someone talking in the background.
The longer you wait, the harder it becomes to reverse changes in the brain that correspond with hearing problems.
Although all participants had normal hearing according to a traditional hearing test, the results show that older people had more trouble understanding speech. It remains fairly stable until the age of 50, but after that it goes downhill quickly. The older participants did show a higher brain activity, which may indicate that they need to use more brain areas to understand speech. This can cause them to tire more quickly, and leaves less brain capacity for other mental processes. "That seems logical, as older people often say that they find it difficult to understand speech," Decruy explains.
Free hearing tests
"This finding strongly indicates that people with seemingly good hearing don’t always understand speech that well," says Francart. "In addition to doing traditional hearing tests, health care providers also need to check whether people understand speech, and advise them on how to deal with a reduced ability to understand speech and the fatigue that comes with this." Especially that last aspect if often not measured now. What’s more, many people don’t know that they can take a free hearing test online or at a hearing centre.
"If you have trouble understanding speech, it’s useful to take such a test, even if you think you don’t have hearing loss," advises Decruy. "It’s crucial to take timely action in case of early hearing problems, because the longer you wait, the harder it becomes to reverse the corresponding changes in the brain," adds Francart.
Eventually, the researchers want to develop training programmes to improve the ability to understand speech. "We’re already doing this for people with hearing loss. And we’re also working on smart hearing aids that adjust their settings based on the brain signals of the person wearing them," Francart concludes.
The study ’ Evidence for enhanced neural tracking of the speech envelope underlying age-related speech-in-noise difficulties ’ by Lien Decruy, Jonas Vanthornhout and Tom Francart was published in the Journal of Neurophysiology. An open access version of the article can be found here.