Working the Night Shift Disrupts Brain Clock

By Carl Engelking | May 14, 2014 2:33 pm

night shift

It is already known that working the graveyard shift can negatively impact health, and the body of evidence continues to grow. Now, researchers have shown that forced nocturnalism may affect the brains’ internal clock in a way that’s similar to Alzheimer’s disease.

The circadian system in mammals orchestrates the daily rhythms of activity and sleep with day and night. Disrupting this cycle throws off physiological balance, and can lead to increased risks of heart disease and diabetes in people.

But until now little has been known about how shift work alters the brain’s master timekeeper.

Simulating the Graveyard Shift

To test the effects of working late, researchers put rats through a simulated work week. Seven rats worked during their typical nocturnal active period, while 12 others were made to work days instead. Both sets of rats logged a typical 5-day work week with weekends, and stayed on the grind for five weeks.

Researchers simulated “work” by placing rats on slowly rotating drums, which required the rats to stay awake and move, but didn’t overexert them. After their shifts, researchers monitored rats’ movements with motion sensors to test for abnormalities.

Within two weeks, rats working the graveyard shift gained a significant amount of weight as their post-work activity decreased. Their activity levels were also more erratic, fluctuating from unpredictable highs to lows. Rats that worked a typical week didn’t change their behavior. Further, a two-day weekend wasn’t enough time to recover from behavioral changes resulting from working the night-shift.

Researchers determined by measuring post-work activity levels that these changes occurred in  rats’ biological clock, or master circadian pacemaker, which is located within the brain. The disruption was so pronounced that the rats’ behavior resembled  animals that had had that region severed. For a human analogy, the rats’ symptoms stemming from a dysfunctional circadian clock were similar to a person diagnosed with dementia.

Researchers published their findings Tuesday in the Journal of the Royal Society Interface.

Some Limits and Consequences

Researchers noted that rats are active at night, while humans are busy during the day, and the effects of the late shift could be varied as a result. Further, the variations in rat activity could be attributable to the stress of moving from cage to cage, but researchers say that is unlikely.

The findings indicate that monitoring night-workers’ activity levels might be a useful way of predicting negative health effects from their unorthodox schedule. Night work is, unfortunately, a fact of life for many – so working to minimize its health risks should help us all sleep better.

 

Photo credit: Sergei Chumakov/Shutterstock

CATEGORIZED UNDER: Mind & Brain, top posts
  • http://blogs.discovermagazine.com Jonathan Tracey

    You neglect to tell us what happened to the day-working rats, as the test would be relatively meaningless if they had the same results.
    If this mistake was made in the original paper, I must fear for the careers of the scientists. If this was your mistake, I only fear for the so-called ‘flac’ you may recieve.

    • Angela Nicole Leister

      The article states that the rats that worked a typical week did not experience any changes in behavior.

  • Andrew

    Those who work the graveyard shift often contend that an hour after midnight is like two hours in the daytime. Most appear to do it for advantageous monetary award rather than by choice. Imagine attempting to sleep this time of year, the Sun shining, lawnmowers and tree surgeons at work with chain saws…..An oft unappreciated endeavour the lot of the unfortunate graveyard shift employee.

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