en Occupational Health Original Article <div style="text-align: justify;"><span style="font-family:Arial;"><span style="font-size:10pt"><span style="line-height:200%"><span style="color:black"><b>Background: </b>Productivity and safety of night shift workers are affected by sleepiness during work. Therefore, interventions to reduce sleepiness are very important. This study was conducted with the aim of determining the effect of light on sleepiness and mouth temperature of hospital night shift workers.</span></span></span><br> <span style="font-size:10pt"><span style="line-height:200%"><span style="color:black"><b>Materials and Methods:</b> This clinical trial study was conducted using light intensity intervention in 140 hospital night shift workers in 2018 with targeted sampling. The Stanford Sleepiness Scale (SSS) was used to determine the sleepiness score. This scale was completed one hour after light interventions at 23 and 1, 3 and 5 in the morning. Also, mouth temperature was measured one hour after starting work at 23, 1, 3, 2, and 4. Finally, the data before and after the intervention were compared and the results were analyzed.</span></span></span><br> <span style="font-size:10pt"><span style="line-height:200%"><span style="color:black"><b>Results:</b> The average sleepiness and mouth temperature were 1.04&plusmn;2.67 and 36.56&plusmn;0.13, respectively. The effect of the intervention on sleepiness was significant (P-value <0.001). The correlation between mouth temperature and sleep was significant (0.033, r = 0.22, P-value). The trend of changes in employees&#39; oral temperature was also significant (P-value < 0.001).</span></span></span><br> <span style="font-size:10pt"><span style="line-height:200%"><span style="color:black"><b>Conclusion: </b>The results showed that the light intensity had a significant effect on sleepiness. But there was no significant effect of light intensity on the mouth temperature of employees and there was a significant inverse relationship between sleepiness and mouth temperature.</span></span></span></span><br> <br> &nbsp;</div> Sleepiness,Shift Work,Iran, 34 41 http://johe.rums.ac.ir/browse.php?a_code=A-10-442-2&slc_lang=en&sid=1 Behzad Khedri 22400319475328460010800 22400319475328460010800 No M.Sc in Social Work, Dept. of Social Work, Faculty of Social Studies, Hanze University of Applied Science, Groningen, Netherlands. Hanze University of Applied Science Seyed Ali Razavi Nasab 22400319475328460010801 22400319475328460010801 No Assistant Prof., School of Medical Sciences, Emam Reza Hospital, Sirjan Faculty of Medical Sciences, Sirjan, Iran. Sirjan Faculty of Medical Sciences Amin Babaei Pouya 22400319475328460010802 22400319475328460010802 No Lecturer, Dept. of Occupational Health and Safety Engineering, School of Health, Ardabil University of Medical Sciences, Ardabil, Iran Ardabil University of Medical Sciences Nasir Amanat 22400319475328460010803 22400319475328460010803 No Assistant Prof., Nursing Care Research Center, Semnan University of Medical Sciences, Semnan, Iran. Semnan University of Medical Sciences Mohsen Amini Zadeh 22400319475328460010804 22400319475328460010804 No Assistant Prof., Health in Disasters and Emergencies Research Center, Institute for Futures Studies in Health, Kerman University of Medical Sciences, Kerman, Iran; Health in Emergency and Disaster Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. University of Social Welfare and Rehabilitation Sciences Javad Hosseini 22400319475328460010805 22400319475328460010805 No M.Sc in Biostatistics, Health Sciences Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Hamadan University of Medical Sciences Tayebeh Ilaghinezhad Bardsiri tayebe.ilaghi@gmail.com 22400319475328460010806 22400319475328460010806 Yes Instructor in Neonatal Intensive Care Nursing, Dept. of Nursing, School of Medical Sciences, Sirjan Faculty of Medical Sciences, Sirjan, Iran. Sirjan Faculty of Medical Sciences Farahnaz Khajehnasiri ٭ khajenasiri@tums.ac.ir 22400319475328460010807 22400319475328460010807 No Associated Prof., Dept. of Community Medicine, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Tehran University of Medical Sciences