Night Shift Work Alters Key Circadian Gene Expression

A recent study published in Frontiers in Endocrinology found that night shift work was associated with distinct changes in circadian gene expression among female healthcare workers (HCWs). The findings suggest that prolonged night-shift work may alter molecular pathways involved in the body’s internal clock.

Key Points

• Female HCWs with night-shift exposure showed lower expression of CLOCK, TEF, PER1, and YY1 genes.
• Longer and cumulative night-shift exposure was associated with changes in CLOCK and TEF expression.
• The findings highlight potential molecular effects of chronic circadian disruption, but they do not establish causality or future disease risk.
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How Does Night Shift Work Affect Circadian Gene Expression?

Circadian rhythms coordinate hormone signaling, metabolism, immune activity, sleep, and gene expression with the light-dark cycle. Repeated work during the biological night can disrupt this timing, particularly when workers experience artificial light exposure and irregular sleep schedules.

Researchers evaluated 93 female HCWs aged 37–66 years, including 47 day-shift workers and 46 night-shift workers. Night work included at least three hours between midnight and 5:00 a.m., with participants maintaining their respective schedules for at least six months.

Morning fasting blood samples were analyzed for several circadian clock genes, including CLOCK, TEF, PER1, PER3, and YY1.

What Did the Study Find About Long-Term Night Shifts?

Night-shift workers had significantly lower peripheral expression of CLOCK, TEF, and PER1 compared with day-shift workers, while PER3 did not show a significant difference. A combined Clock Gene Expression Score was also lower among night-shift workers.

TEF showed the clearest ability to distinguish night-shift workers from day-shift workers, followed by PER1 and CLOCK. Researchers also found that longer night-shift exposure was associated with lower CLOCK and TEF expression, while greater cumulative exposure was associated with lower TEF expression.

YY1 expression was also lower among night-shift workers, particularly among those with longer-term or higher cumulative exposure. Sleep duration showed positive associations with TEF and the combined gene-expression score, while sleep dissatisfaction showed negative associations.

These findings suggest that chronic circadian disruption may influence relationships among peripheral clock genes rather than affecting individual genes in isolation.

What Could These Findings Mean for Healthcare Professionals?

The study provides a molecular perspective on the effects of prolonged night shift work among female HCWs. However, its cross-sectional design cannot establish whether night shifts caused the observed gene-expression changes.

Researchers did not directly measure circadian phase, and peripheral blood expression may not represent circadian activity in other tissues. The relatively small sample and lack of independent validation also limit the findings.

Importantly, the study does not show that these gene changes cause cancer or other diseases. The researchers noted that the changes could reflect either biological disruption or a compensatory response to repeated circadian stress.

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For clinicians and occupational health professionals, the findings reinforce the need for longitudinal research examining whether circadian gene changes persist, reverse after schedule changes, or relate to measurable health outcomes among long-term night-shift workers.

Source:

Frontiers In