Preventing hearing loss is a matter of looking at these factors and seeing what can be controlled and what is not preventable. Consider noise exposure: wearing good hearing protection is a great preventative.
As far as I am aware, there has been plenty of research regarding genetics and hearing loss but no epiphanies on preventing hearing loss due to aging.
Research on treating hearing loss again depends on the cause of the hearing loss. If the hearing loss was due to noise exposure or another process causing permanent nerve damage, then typically hearing aids are the treatment most often recommended.
There is plenty of information and research being done in conjunction with hearing assistive devices (i.e. hearing aids, cochlear implants and FM systems).
Again, I know of no treatment to reverse permanent hearing loss due to aging, illness or noise exposure. Prevention is the best treatment. If you are exposed to loud noises, wear hearing protection. Discuss your medications and medical treatments with your physician to see if there are any possible side effects that might be related to permanent hearing loss. If treatments are needed, your audiologist or physician can give you some options to explore. Hearing aids and hearing devices are the most common form of treatment for permanent hearing loss.