en Occupational Medicine Occupational Medicine Original Research Original Research <p> <strong> Background </strong>:Work ability assessment and its affecting factors are important in the field of occupational health. One of the factors affecting work ability is sleep disorder, which is very common among workers. Therefore, the present study aimed to assess work ability and its relationship with sleep disorder in workers of a manufacturing plant. </p><p> <strong> Methods </strong>: This cross- sectional study was conducted in a manufacturing plant in Tehran in 2013. All the 931 male workers of this plant were enrolled in the study, and their work ability was assessed using the Work Ability Index (WAI). The scores of this index range from 7 to 49, and the higher work ability score indicates a better work ability status. In this study, sleep disorder was assessed using the MUSIC-Norrtalje Questionnaire. </p><p> <strong> Results </strong>: The average score of WAI was 42.81, ranging from 22 to 49. This score was significantly lower in the group with sleep disorder (41.28) than in the group without sleep disorder (44.10) (p< 0.001). The results of the logistic regression analysis revealed a significant relationship between work ability and sleep disorder even after adjustment for the confounding variables (OR= 2.52, 95% CI= 1.07 – 5.93, p= 0.033). </p><p> <strong> Conclusion </strong>: The results of this study found a relationship between sleep disorder and work ability. Therefore, it is recommended to identify workers with sleep disorder and attend to their problem in order to increase their work ability. </p> Work Ability, Sleep disorder, Worker. 727 734 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-738&slc_lang=en&sid=1 Yasser Labbafinejad ylabbafinejad@yahoo.com 200319475328460013627 200319475328460013627 No Occupational Medicine Department and Occupational Medicine Research Center, Iran University of Medical Sciences, Tehran, Iran. Mostafa Ghaffari m_ghafaari@yahoo.com 200319475328460013628 200319475328460013628 No Brain and Spinal Injury Research Center (BASIR), Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Baharak Bahadori bahadori_baharak@yahoo.com 200319475328460013629 200319475328460013629 No Occupational Medicine Department, Iran University of Medical Sciences, Tehran, Iran. Saber Mohammadi sabermohammadi@gmail.com 200319475328460013630 200319475328460013630 No Occupational Medicine Department, Iran University of Medical Sciences and Brain and Spinal Injury Research Center (BASIR), Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Alireza Abdi persia_ab@yahoo.com 200319475328460013631 200319475328460013631 No Brain and Spinal Injury Research Center (BASIR), Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Mohamad Namvar mohamad.namvar@gmail.com 200319475328460013632 200319475328460013632 No Occupational Medicine Department, Iran University of Medical Sciences, Tehran, Iran. Mirsaeed Attarchi msattarchi@yahoo.com 200319475328460013633 200319475328460013633 Yes Occupational Medicine Department, Iran University of Medical Sciences and Brain and Spinal Injury Research Center (BASIR), Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran.