Disruption of central and peripheral circadian clocks in police officers working at night

What is it about?

Working night shifts often leads to a desynchrony between internal body clocks and the outside light-dark cycle. This desynchrony is associated with various health issues. Although several studies have shown such a desynchrony for the central clock, located in the brain, very few studies have addressed what happens to other clocks located throughout the body. In this study, we studied police officers, who work 7 consecutive night shifts as part of their regular work schedule. We studied two central clock markers, urinary 6-sulfatoxymelatonin and salivary cortisol, and gene expression in two peripheral clocks, white blood cells and oral mucosa cells. We observed that before working a week of night shifts, the central clock and the peripheral clocks of these police officers' were well synchronized to their day-oriented schedules. In contrast, after a week of night shifts, whereas the central clock showed some adaptation to the shifted schedule, the peripheral clocks of the police officers showed an absence of daily rhythm. This shows that a disruption of peripheral clocks can occur as a result of working night shifts. These findings have important clinical implications for the occurrence of medical disorders associated with shift work.

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