The odds ratio for hearing shift for workers who reported never versus always wearing hearing protection was nonsignificant for OSTS (OR 1.23, 95% CI 0.92-1.64) and marginally significant for HFTS (OR 1.26, 95% CI 1.00-1.59). A significant linear trend towards increased risk of HFTS with decreased use of hearing protection was observed (P = 0.02).