Investigating the Circadian Rhythm Type and its Relation to the Problems Caused by Shift work: a Case Study-Workers in one of Iran’s Iron-Ore Mines

Nowadays, shift work systems are a very common work schedule in developed and industrialized societies. The human body needs to adapt itself to different cycles of sleep and awakening. These will predispose persons to various physical, psychological, and social problems. This study was aimed to investigate the circadian rhythm type among workers in one of Iran’s iron-ore mines. Furthermore, the relationship between the circadian rhythm amplitude and stability was also evaluated. In the present cross-sectional study, 356 persons were investigated who were working in their daily shift work in an iron-ore mine. The samples were collected randomly and for data collection, the standard questionnaires of “Survey of Shift Workers” (SOS) and “Determination Checklist of Circadian” (CTI) were used. Data were analyzed using SPSS software version 11. ANOVA, T-test, and Chi-square tests were applied. According to the research objectives, 356 participants, 75.2% (268 persons) were shift-workers, and 24.8% (88 persons) were fixed-shift workers. The average age of the shift workers was 35.22 ± 5.40 year-olds. In addition, the most frequent reason for choosing a night-shift for the shift workers was organizational constraints (57%). The results showed that working based on shift work schedule had a significant effect on individual activities (p = 0.034) and family life (p = 0.0001) compared to fixed-shift workers. It was also found that among inflexible individuals, problems such as digestive and psychological problems were less specified than shift workers. Shift-workers with stable circadian rhythms showed more flexibility to the sudden changes occurring in their inner rhythm and relatively had less shift-working issues. On the contrary, those who had rigid circadian rhythm, they were resistant to sudden changes. Consequently, these individuals were susceptible to problems caused by shift work. Stability (FR) and amplitude (LV) variables of circadian rhythms can be used as predictive indicators for employment and help to select appropriate individuals for the shift work system to prevent the occurrence of shift-working problems.