The cited study lacks an acceptable positive control of users who talked on non cellular (EMF) emitting telephones for similar duration of time. As it is widely known that prolonged exposure to loud noise (like one from talking on a phone) can lead to hearing loss (which was what the cited study was testing for). Not surprisingly the study found that users who talked on the phone less had better hearing. I don't feel their conclusion is justified by the experimental design.
I am sorry you have troublesome ears. Have a great one.