January 26, 2014
Shift Work And Jet Lag – How They Make You Ill
Working lates or shifts, or even taking regular flights across time zones, can seriously damage your health. To understand why this happens we need to what goes on deep inside the human brain. If you could open up your head and peer inside you would see at the base of your brain a tiny area known as the hypothalamus. Although only the size of a large pearl, this is where many of your basic functions are processed. It may be small, but without it you’d die and if it is damaged, then you will malfunction. For this is your regulator, integrating functions that are essential for survival like feeding and energy metabolism, the intricate mechanisms of fluid and electrolyte balance, and controlling body heat, stress levels, and even sexual reproduction. The hypothalamus is your best friend and can be like your worst enemy if it doesn’t play ball.
This little pearl has one other major function: your internal clock. Inside the hypothalamus is an even smaller area the size of a grain of rice known as the suprachiasmatic nucleus (SCN) which in effect switches on or off certain body processes in a “circadian rhythm” approximately 24 hours long. Consisting of around 50,000 neurons, the SCN triggers changes in the endocrine system to produce hormones that wake you up or shut you down. The problem is that in order to maintain a regular 24 hour cycle, the SCN needs external stimuli, such as changes in daylight hours and it is therefore directly connected to the eye’s retina. Any changes to a person’s own sleep and waking rhythm (like that vacation flight or working nights) leads to the body becoming out of sync with the internal clock.
Now new research has shown just how this disruption might work and how the implications for long term health are worrying. The researchers delayed the sleep of their subjects by 4 hours on each of three consecutive days by controlling lighting in their environment, effectively giving them a 28 hour day. By checking gene levels in blood samples before, during, and after the experiment, they found that this de-synchronisation caused disruption to more than 1,000 genes many of which are essential for the maintenance and repair of the body. Hundreds of these genes whose levels normally rise and fall lost their basic rhythm while many that do not normally have fluctuating levels began to develop abnormal cycles. Only around 40 genes maintained their normal rhythms. The study’s authors believe that this “profound” disruption must have “negative outcomes” for general health, though they do not attempt to quantify or predict what these risks might be.
The findings were surprisingly similar to the changes that occur in ageing when the daily rise and fall of gene expression becomes weaker. Pulling that double shift or flying to Japan is in effect making you that little bit older every time you do it. Normally, the body’s internal clock will adjust fairly quickly to minor or infrequent changes, but regular or severe disruption means the circadian rhythm never recovers.
With approximately one in five US employees working shifts (which take them outside 6am to 6pm) and one in fifteen working lates permanently, this research adds to the existing body of knowledge that jet lag and shift work are truly bad for the health of the individual and has wider implications for society as a whole.
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