From the abstract:
We examined the association between self-reported hearing protection use at work and incidence of hearing shifts over a 5-year period….
The odds ratio for hearing shift for workers who reported never versus always wearing hearing protection was nonsignificant for OSTS and marginally significant for HFTS. A significant linear trend towards increased risk of HFTS with decreased use of hearing protection was observed.
The study raises concern about the effectiveness of hearing protection as a substitute for noise control to prevent noise-induced hearing loss in the workplace.