1Associate Professor, Research Center for Health Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
2Ph.D. Student of Occupational Health, School of Health, Hamedan University of Medical Sciences, Hamedan, Iran
3Assistant Professor, Epidemiology Department, School of Health and Nutrition, Shiraz University of Medical Sciences, Shiraz, Iran
4Ph.D. Student of Occupational Health, School of Health, Tehran University of Medical Sciences, Tehran, Iran
Background & Aims: Shift work is programmed in various schedules, each has its own advantages and
disadvantages. The main purposes of this study were: a) to determine common shift schedules used in
petrochemical industries, b) to compare shift work health-related problems among employees working in
different shift schedules and c) to recommend appropriate shift schedule.
Methods: This cross-sectional study was carried out at 14 petrochemical companies. Study population
consisted of 987 shift workers. Data on demographic features, shift schedule and adverse effects of shift
work were collected via anonymous questionnaire. Statistical analyses were performed using SPSS, version
Results: Among 987 studied shift employees, 27% worked in 3M-3E-3N-3Res, 61% in 4M-4E-4N-4Res
and 12% in 12-hour schedules. Health problems such as gastrointestinal, cardiovascular and musculoskeletal
disorders among 4M-4E-4N-4Res schedule shift workers were significantly less prevalent than other
schedules (P<0.05). Furthermore, the results showed that the prevalence rates of health problems among 12-
hour schedule shift workers were higher than 3M-3E-3N-3Res schedule workers.
Conclusions: Since 12-hour schedule caused higher rates of gastrointestinal, cardiovascular and
musculoskeletal disorders among shift workers as compared with 4M-4E-4N-4Res and 3M-3E-3N-3Res
schedules, it should be avoided in shift system. Based on the results, 8-hour schedules with clockwise rapid
rotation are recommended.