This is a common problem affecting millions of people worldwide. Some causes are avoidable, some are not. Some are genetic, some are acquired. There are two main groups of deafness; sensorineural and conductive.
Sensorineural causes include deafness due to increasing age (presbyacusis) and due to nerve damage. Also in this category is noise induced hearing loss. This is hearing loss secondary to exposure to noise of high volume. To begin with, this may be reversible, but finally it becomes permanent. It tends to be tied up with tinnitus. This case of deafness is extremely relevant because it is entirely preventable by wearing earplugs. ZenPlugs are amazingly comfortable and effective so are worth a try.
Conductive hearing loss is caused by a blockage to the sound vibrations. This occurs between their origin and the sensory apparatus.
There are many reasons for this including impacted ear wax and a perforated ear drum. These causes are reversible and sometimes are avoidable. Impacted wax is often the consequence of careless use of ear buds. It can be removed using ear drops and/or suctioning. Syringing of the wax is not recommended any more as it can induce tinnitus and suctioning is far more efficient.
A perforated eardrum also causes conductive hearing loss. This can be induced by infection, scuba diving, foreign body in the ear and flying in an aeroplane. These usually heal on their own but occasionally require surgical intervention for a repair.