مقایسه خواب و عملکرد ذهنی در نوبت‌های کاری هشت و دوازده ساعته در یکی از پالایشگاه‌های نفت ایران

Background: There are different types of shift work programs, each of them has its pros and cons. The purpose of this study was to compare sleep and mental performance in 12-hour and 8-hour shift works. Methods: In this longitudinal study, 61 workers from 187 shift workers in one of oil refinery plants were chosen. They were supposed to work in a schedule of 12- hour shift works for 6 months and then return to 8-hour shift works again. We used a demographic questionnaire, sleep diary and PVT software in the beginning and the end of the same shift. Data was collected at the end of 6 months of 12-hour shifts and then after 6 months of 8-hour shifts from the same workers. Results: Total sleep time mean in 12-hour shifts was 6.20 hours and in 8-hour shifts was 6.41 hours, but the difference was not significant. The difference between means of reaction times in the beginning of 12-hour shifts (451.80 milliseconds) and 8-hour shifts (416.12 milliseconds) was not significant. The difference between means of reaction times in the ending of 12-hour shifts (382.22 milliseconds) and 8-hour shifts (390.98 milliseconds) was not significant either. The difference between means of false responses in the beginning of 12-hour shifts (3.74) and 8-hour shifts (2.98) was significant. (p<0.05) This difference in the ending of the shifts was significant as well. (3.74 in 12-hour versus 2.36 in 8-hour shifts, p, 0.01). Conclusion: Total sleep time in 12- hour shifts is not significantly different from 8-hour shifts. 12-hour shift may decrease mental function (increasing false responses of PVT in the beginning of 12-hour shifts comparing to 8-hour shift). Different sleep patterns may be an explanation for these findings. Key words: 12-hour and 8-hour shift works, Mental performance, Reaction time, False responses