title: The association between long working hours and hearing impairment in noise unexposed workers: data from the 5th Korea National Health and Nutrition Examination Survey (KNHANES 2010-2012).
abstract: BACKGROUND
  This study is aimed at finding out the relationship between long working hours, one of major job stress elements, and hearing impairment in unexposed workers to occupational and environmental noise.
  
  
  METHODS
  This study was performed on 1628 regular, full-time wage workers between the age of 25-64 who indicated in the survey of having no experience of exposure to noise, normal otoscopic findings, and not suffering from diabetes based on the data from the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2010-2012). The average working hours per week was categorized into 40 h and lower group, more than 40 to 48 h group, more than 48 to 60 h group, and more than 60 h group. The groups were defined as suffering from low or high frequencies hearing impairment if the average hearing threshold for 0.5, 1, 2 kHz or 3, 4, 6 kHz in both ears exceeds 25 dB based on the pure tone audiometry. The association between average weekly working hours and hearing impairment was analyzed using logistic regression after gender stratification.
  
  
  RESULTS
  The prevalences of low and high frequencies hearing impairment in male workers were 4.3 and 28.6 %, respectively, which were much higher than female's prevalence of 2.7 and 11.1 %. For male workers, no significant association was found between average weekly working hours and low and high frequencies hearing impairment. For female workers, odds ratios (OR) of low and high frequencies hearing impairment were 4.22 (95 % confidence interval (CI) 1.09-16.27) and 4.49 (95 % CI 1.73-11.67), respectively, after controlling for several related factors, such as, age, Body Mass Index (BMI), socio-economic status, health-related behavioral, and occupational characteristics variables, in the final model in the group working more than 60 h compared to the group working 40 h and lower. In addition, a dose-response relationship was observed that ORs of low and high frequencies hearing impairment were increased according to increasing average weekly working hours.
  
  
  CONCLUSIONS
  The association between long working hours and hearing impairment in both low and high frequencies was significant in Korean female workers with a dose-response relationship. Therefore, the law to change the culture of long working hours should be enacted in order to protect the workers' health and improve the quality of life in Korean workers.
authors.affiliation: Department of Occupational and Environmental Medicine, Kyung Hee University Hospital, Seoul, South Korea.
authors.forename: Jung-Woo
authors.initials: JW
authors.lastname: Park
authors.affiliation: Department of Occupational and Environmental Medicine, Kyung Hee University Hospital, Seoul, South Korea.
authors.forename: Jin-Soo
authors.initials: JS
authors.lastname: Park
authors.affiliation: Department of Occupational and Environmental Medicine, Kyung Hee University Hospital, Seoul, South Korea.
authors.forename: Seyoung
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Occupational and Environmental Medicine, Kyung Hee University Hospital, Seoul, South Korea.
authors.forename: Minkyu
authors.initials: M
authors.lastname: Park
authors.affiliation: Department of Occupational and Environmental Medicine, Kyung Hee University Hospital, Seoul, South Korea ; Department of Occupational and Environmental Medicine, School of Medicine Kyung Hee University, Seoul, South Korea.
authors.forename: Hyunrim
authors.initials: H
authors.lastname: Choi
authors.affiliation: Department of Occupational and Environmental Medicine, Kyung Hee University Hospital, Seoul, South Korea ; Department of Occupational and Environmental Medicine, School of Medicine Kyung Hee University, Seoul, South Korea.
authors.forename: Sinye
authors.initials: S
authors.lastname: Lim
keywords: Hearing impairment; KNHANES; Long working hours