Comparisons of hearing threshold changes in male workers with unilateral conductive hearing loss exposed to workplace noise: a retrospective cohort study for 8 years.
10.1186/s40557-016-0132-1
- Author:
Sang Jin PARK
1
;
Joo Hyun SUNG
;
Chang Sun SIM
;
Seok Hyeon YUN
;
Jeong Han YEOM
;
Joong Keun KWON
;
Jiho LEE
Author Information
1. Department of Occupational and Environmental Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, 877 Bangeojinsunhwando-ro, Dong-gu, Ulsan, 44033 Republic of Korea. oemdoc@naver.com
- Publication Type:Original Article
- Keywords:
Conductive hearing loss;
Noise-induced hearing loss;
Noise;
Retrospective cohort study
- MeSH:
Biochemistry;
Cohort Studies*;
Ear;
Follow-Up Studies;
Hearing Loss, Conductive*;
Hearing Loss, Noise-Induced;
Hearing Loss, Sensorineural;
Hearing*;
Humans;
Male*;
Noise*;
Physical Examination;
Retrospective Studies*;
Ulsan
- From:Annals of Occupational and Environmental Medicine
2016;28(1):51-
- CountryRepublic of Korea
- Language:English
-
Abstract:
BACKGROUND: The purpose of this study was to investigate hearing threshold changes of workers with unilateral conductive hearing loss who were exposed to workplace noise for 8-years. METHODS: Among 1819 workers at a shipyard in Ulsan, 78 subjects with an air-bone gap ≥10 dBHL in unilateral ears were selected. Factors that could affect hearing were acquired from questionnaires, physical examinations, and biochemistry examinations. Paired t-test was conducted to compare the hearing threshold changes over time between conductive hearing loss (CHL) ear and sensorineural hearing loss (SNHL) ear. RESULTS: The study included male subjects aged 48.7 ± 2.9, having worked for 29.8 ± 2.7 years. Hearing thresholds increased significantly in CHL ears and SNHL ears at all frequencies (0.5–6 kHz) during follow-up period (p < 0.05). The threshold change at 4 kHz was 3.2 dBHL higher in SNHL ears which was statistically significant (p < 0.05). When workers were exposed to noise levels of 85 dBA and above, threshold change at 4 kHz was 5.6 dBHL higher in SNHL ears which was statistically significant (p < 0.05). Among workers aged below 50, the threshold change values were lower in low-frequency (0.5–2 kHz) in SNHL ears, with a small range of changes, whereas in high-frequency (3–6 kHz), the range of changes was greater SNHL ears (p < 0.05). Among workers aged 50 and above, SNHL ears showed a wider range of changes in both high- and low-frequency areas (p < 0.05). CONCLUSIONS: At high-frequencies, particularly at 4 kHz, the range of hearing threshold changes was lower in ears with conductive hearing loss than in contralateral ears. This is suggested as a protective effect against noise exposure.
