Cats can lose their hearing for many reasons, just like humans do. Deafness can be caused by inflammation or infection, degenerative nerve changes, traumatic injury or certain drugs. Some cats are born deaf. It appears that white cats with blue eyes are particularly prone to congenital deafness. There is also a breed connection; some of the breeds that are at higher risk are white Persians, Ragdolls, Cornish and Devon Rex, Oriental Shorthairs, Manx and Turkish Angora.
Deafness that occurs as a result of old age will be a gradual process. The eardrums become less flexible, and sound is not transmitted as effectively.
In a recent article for Answers.com, I explained how you can recognize whether your cat is deaf, and how to communicate with a deaf cat and make her life easier. Click here to read the full article.