But when the signals reach their aging brains, things begin to go wrong. The findings were presented at a recent conference of the Association for Research in Otolaryngology.

A variety of changes in the brain may be to blame, and they may also affect how well people process signals from the other senses, said one of the researchers, Robert Frisina of the University of Rochester Medical Center.

In earlier research, for example, Frisina and colleagues found that as some people grew old, their brains had trouble keeping pace with the tiny gaps that occurred in understanding, making it harder to follow what was being said. This may also be a signal of more trouble ahead.

If a hearing problem does not involve the ear, standard treatments are of no use.

But as researchers get a better understanding of the problem, Frisina said, they may find that drugs like those used to treat other neurological conditions can help restore the chemical imbalances behind the problem.

By Eric Nagourney