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Effect of stress on circadian rhythms

Scientists based at Waseda University (Japan) have discovered how different levels of stress can affect the body’s internal clock, or circadian rhythms. Circadian rhythms are physical, mental and behavioral changes which follow a 24-hour cycle, influenced by light and darkness in a person’s environment.

Circadian rhythms affect most living organisms — they are in tune with a 24-hour cycle and sensitive to day and light. This is why, for example, shift workers sometimes suffer with illnesses because they are working when the body expects to be sleeping and sleeping during the daytime. Circadian rhythms are tied to various physiological functions.

Previous research suggests stress hormones can affect how the internal body clock functions. Waseda University researchers have built upon this in a new study. Carrying out studies using mice, a research group discovered that when a body is subjected to stress prior to sleeping this has considerable influence on biological rhythms. Furthermore, this is a far greater effect then when a body is subjected to stress just after waking. The effect of stress impacted on various physiological functions and the nervous system (including the brain.)

The researchers conducted their studies in this way in order to examine the impact of night-shift work on the body. By running various simulations with rodents, they found that the impact of night-shifts can be lessened if the most stressful activities are carried out at the start of the work pattern rather than at the end. It also stands that a slow build up to stress at the start of the day helps to build-up tolerance.

The findings have been published in the journal Scientific Reports. The paper is titled “Entrainment of the mouse circadian clock by sub-acute physical and psychological stress.”

In related news, research suggests human responses to various cancer therapies could be stronger when administered at particular times during the day.

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Dr. Tim Sandle is Digital Journal's Editor-at-Large for science news. Tim specializes in science, technology, environmental, business, and health journalism. He is additionally a practising microbiologist; and an author. He is also interested in history, politics and current affairs.

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