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چکیده
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INTRODUCTION: The aim of this study was to evaluate the effects of consecutive night shifts (CNS) and shift length (SL) on cognitive performance and sleepiness. MATERIALS AND METHODS: This study evaluated the sleepiness and performance of 30 control rooms operators (CROs) working in a 7 nights, 7 days, 7 days off (7N7D7O) and 30 CROs working in a 4 nights, 7 days, 3 nights, 7 days off (4N7D3N7O) shift pattern in a petrochemical complex in the last night shift before swinging into the day shift. To assess the cognitive performance, n-back test, continuous performance test (CPT) and simple reaction time test were employed. For assessing sleepiness the Karolinska sleepiness scale (KSS) were used. RESULTS: Results from the both schedules indicated that the correct responses and responses time of working memory were reduced (p= 0.001), while intentional errors and sleepiness increased during the shift work (p= 0.001). CNS had a significant impact on reaction time and commission errors (p = 0.001). CONCLUSION: The main duty of CROs at a petrochemical plant is checking hazardous processes which require appropriate alertness and cognitive performance. As a result, planning for appropriate working hours and suitable number of CNS in a rotating shift system is a contribution to improving CROs performance and enhancing the safety.
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