Comparison of Melatonin Profle and Alertness of Firefghters with Different Work Schedules

A two-shift work schedule with different rotations is common among frefghters in Iranian
petrochemical companies. This study compared salivary melatonin and sleepiness on the last night before
turning to day shift at 19:00, 23:00, 3:00, and 7:00 among petrochemical frefghters (PFFs) working
seven and four consecutive night shifts.
Methods: Sixty four PFFs working in the petrochemical industry were selected. To measure melatonin,
saliva samples were taken, whereas the KSS index was used to assess sleepiness. Chi-square and independent
samples t-test were carried out to analyze the data, and generalized linear model (GLM) was employed to
determine the effect of confounding factors such as lighting and caffeine.
Results: The levels of melatonin at 3:00 and 7:00, and the overall changes during the shift in the two
shift patterns under the study were different (P < 0.05). Sleepiness was signifcantly different only at
3:00 in the two studied shift patterns, while the effects of lighting and caffeine on melatonin changes
were not signifcant (P > 0.05).
Conclusion: It seems that a slow shift rotation is better because it reduces the secretion of melatonin
(hence reducing sleepiness during the night) and changes the peak of melatonin secretion to the daytime,
which is a sign of adaptation