The Battle Between Your Body Clock And The Mechanical Clock

Aug 12, 2013

It's not easy to adjust to a new time zone or work schedule. Our body has a natural sleep/wake cycle and disruptions to it can lead to more than just feeling tired or exhausted.

Washington University professors Paul Gray and Erik Herzog are studying the biology behind our daily internal clock, or circadian rhythm. Sometimes referred to as the body or biological clock, Herzog defined it as "the entity within the body that synchronizes with an environmental cycle." This is not to be confused with the biological clock some refer to when thinking of a woman's desire to conceive. 

According to Gray, all complex life forms maintain a circadian rhythm. In mammals, the main environmental influence is the sun.

"We receive light information from our eyes, and that information about dawn and dusk is essential to synchronize to the normal light/dark schedule," Herzog said. 

But when that 24-hour cycle of dawn to dusk is disrupted by jet lag, long work shifts or pulling an all-nighter to finish a paper, the body reacts.

"If you leave that cycle, that has a number of consequences. Obviously, one, you don't get the right amount of sleep, or are uncomfortable," Gray said. "But there are also aspects of long term changes to blood pressure, changes in how we respond to blood sugar in our diets...A continuous sort of long term or abrupt changes can actually have a lot of effects on how healthy one is."

Rodney Hall has felt the effects of continuous changes to his sleep cycle. As a firefighter and paramedic for the Edwardsville Fire Department, he has worked 24 hours on, 48 hours off for 18 years.

"Up until a few years ago, if I had a bad night at work, when I got home I'd have to lay down for at least a couple of hours," said Hall. "I'd eat a lot of fast food. If I got back from a call at midnight, I'd grab a cheeseburger and a coke."

It would take Hall the first day off-duty to recover, and he was gaining a lot of weight and feeling generally unhealthy. Two years ago, he began making a concerted effort to eat healthier foods and stick to a regular daily eating and sleeping pattern. Hall was able to lose the weight and is now able to wake up at a normal time the first day home from work.

"For the most part, I have a pretty good routine that I stick to, and I don't feel the lag unless I have a really bad night," Hall said. "I used to be able to tell-my cognitive function used to be affected, but I don't see that since I changed my lifestyle."

Herzog and Gray have identified eight genes that are clearly connected to the circadian clock, and have found that the cells containing the clock will run indefinitely even when removed from the body.  They have also found that the evolution of these genes dates back to the development of multicellular organisms, making the 'parts' of our biological clock some of the oldest still in use by our bodies. 

Despite being somewhat naturally flexible, to account for natural daily and seasonal changes, researchers haven’t found an easy way to adjust our circadian rhythms to abrupt changes. Nor will they.

"It's not really possible to defy the clock," said Gray. "It's as functional as your kidneys. The best you can do is try to accommodate your clock."

And the consequences of trying to defy the clock can be dire. Herzog said pre-diabetic indicators have been found after just three days of a disrupted sleep cycle. Rodents put on a continuously shifting cycle of being woken up two hours earlier every two weeks have been shown to die prematurely, he added. Further, carcinogenic consequences are thought to be the result of continued disruption to our circadian rhythm. In 2007, the World Health Organization listed night shift work as a "probable human carcinogen."

To help you determine your circadian rhythm and find out how closely your sleeping habits align with your sleep cycle, Herzog recommended doing a quick survey called the Munich Chronotype Questionnaire. That can be one step towards finding the best way to align your schedule to your body's needs.

St. Louis on the Air provides discussion about issues and concerns facing the St. Louis area. The show is produced by Mary EdwardsAlex Heuer and Sarah Skiӧld-Hanlin and hosted by veteran journalist Don Marsh.

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