Shift workers could be treated with therapy to put body clocks back in sync

Shift workers could be treated with light therapy to put their body clocks back in sync, according to new research.

A study has shown how exposure to bright lights at night reduces melatonin, a hormone that regulates the circadian rhythm.

The findings could also lead to new therapies for depression, that interrupts sleep.

Scientists tested the association between melatonin suppression body clock disruption in participants who received either continuous or intermittent bright light exposure at night.

Each individual completed a nine to 10 day inpatient study at Brigham and Women’s Hospital, Boston, under highly controlled laboratory conditions.

Their sleep/wake, activity and light/dark schedules were closely monitored.

When they were intermittently exposed to different routines they were found to show significant shifts in their body clock.

Moreover, each and every intermittent bright light pulse induced a similar degree of melatonin suppression.

Lead author Dr Shadab Rahman said: “Overall, our data suggest that melatonin suppression and phase resetting are sometimes correlated, but ultimately are regulated by separate neurophysiological processes.

“Therefore melatonin suppression is not a reliable surrogate for phase resetting. This is an important consideration for developing light-therapy treatments for people who have poor quality sleep and biological clock disruption, such as shift workers, or disorders such as depression.”

The study published in The Journal of Physiology shows the effects of night-time light exposure on the internal body clock.

It follows a study last week that found Modern street lamps are triggering thousands of cancer cases, according to new research.

A study found men living in large cities are twice as likely to develop prostate cancer while women are one and a half times more prone to breast cancer.

Scientists blame the worrying trend on the ‘blue light’ emitted by mobile phones, computers and other screens. This reduces levels of melatonin which controls the body clock.

Both forms of the disease have been street lights and mobile phones could increase the risk of prostate and breast cancer by reducing melatonin. Both diseases are linked to a lack of the hormone which is produced during sleep.

The body has an internal clock that causes various physiological processes to oscillate in 24-hour cycles, called circadian rhythms, which includes daily changes in sleepiness.

Light is the main environmental time cue that resets the body’s internal clock.

Melatonin is produced in the brain and regulates this body clock. It is believed exposure to light before bedtime may reduce sleep quality by suppressing its production.

The researchers aimed to explore the link between the physiological process that enables our internal body clock to synchronise to external time cues (i.e. day and night) – called circadian phase resetting – and suppression of melatonin.

Melatonin suppression and circadian phase resetting are often correlated such that high levels of melatonin suppression can be associated with large shifts of the body clock.

This association between the two responses has often been assumed to represent a functional relationship, resulting in the acceptance that one could be used as a proxy measure for the other.

But the study found found the magnitude of the shift in internal body clock is functionally independent from melatonin suppression.

This knowledge may shape future research designed to improve treatments for depression and shift work sleep disorder.

Added Dr Rahman: “Additional work is needed to optimize light therapy protocols used as treatment.”

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