For years, scientists have been studying the health of people with staggered working hours, particularly those who work night shifts. They seek to determine the impact of these working hours on our biological functions.

Now, a study published in the Journal of Proteome Research sheds further light on this issue, with researchers at Washington State University and the Pacific Northwest National Laboratory confirming that night-shift work can have a profound effect on human bodies.

“There are processes tied to the master biological clock in our brain that say day is day and night is night… and when internal rhythms are dysregulated, you have this enduring stress in your system that we believe has long-term health consequences,” said senior study author Hans Van Dongen.

Van Dongen and colleagues were able to demonstrate this when they asked volunteers to work in rotation for three days – that is, to work shifts either during the day or night. The experiment was carried out under laboratory conditions so the academics could measure the participants’ biological rhythms without the influence of external events.

Blood samples were taken at regular intervals throughout the experiment and analysed to identify proteins present in immune-system cells. These proteins follow biological rhythms, which are often synchronised with the internal body clock to regulate physiological phenomena.

The experts found that protein rhythms were profoundly altered by nighttime work – for example, those regulating blood sugar levels were almost completely reversed in volunteers who worked at night.

They also found that the processes involved in insulin production and sensitivity, which normally act in unison to maintain glucose levels within an optimal range, were no longer synchronised in these participants.

The authors believe this phenomenon is linked to the fact that insulin production fluctuates not just with meals but also with our biological clock. During the night, the body naturally reduces its sensitivity to insulin, enabling more stable regulation of blood glucose levels in the absence of food intake. This adaptation prevents an abnormal drop in blood sugar levels.

Working at night upsets this balance, which can have serious medical consequences. Indeed, studies have shown that working shifts is a probable risk factor for type-2 diabetes, as well as obesity and being overweight.

The results of this study demonstrate the health risks associated with working at night. More research is needed, however, to determine whether night shifts induce long-term protein changes.