Brain link to age hearing loss

THE inability to hold a conversation because of background noise is seen by many as the first sign their hearing is starting to go.

But scientists have found older people find it harder not because they cannot hear, but simply because their brain needs longer to process information.

As we get older our brain signals change, according to a study in the Journal of Neurophysiology. While someone may hear speech as well as they ever did, the cortex, the area of the brain specialising in processing speech, does not work as well.

The result is that older people appear less able to tune out sounds around them.

Researchers at the University of Maryland discovered this by playing three voices in unison to people with normal hearing, aged 61 to 73, and scanning their brains for electrical activity. Researcher Jonathan Simon said: ‘Older people need more time to figure out what a speaker is saying. The older brain just drops part of the speech signal, even if the ears captured it just fine.’

A recent study found almost four in five people with hearing loss have left a restaurant early because it is too loud, with intrusive music and background noise an aggravating factor. But the latest research suggests this is also a problem for people with normal hearing. Older people with good hearing still score significantly worse than people aged 18 to 30 on understanding what is being said in noisy environments.

This was tested by listening to a man reading one story at the same time as a woman read another in the background. When asked to count how often certain words were repeated in the main story, the older group struggled.

Researchers examined the mid-brain, which carries out basic sound processing, and the cortex, part of which focuses on speech. In the younger group, the midbrain generated a signal indicating speech was clearly discernible against a noisy background, but in older people the same signal was degraded.