Shift Work, Jet Lag, Cancer and Your Circadian Rhythm

By Dan

We are all aware of night and day, and the human habits that coincide (generally) with each time. We wake up, eat, work, eat, sleep, and so on…

Dr. Andrea Meredith, Assistant Professor of Physiology at the University of Maryland School of Medicine, joined us here at the Science Center to explain this concept in-depth.

This month’s Tuesday Talk, Rock Around the Clock: How the Brain Encodes Time, unraveled some of the mysteries of our circadian cycle. Circadian, (which means “about a day”) refers to the 24-hour cycle of the physiological processes in living beings.

On the surface this might not seem so exciting, but with bagel and coffee in-hand (thanks, Science Center!) I settled in for what proved to be quite an interesting presentation.

Dr. Meredith explained why we have this circadian cycle, first using behavioral examples from plants. In the 1700′s, it was observed that plants open their leaves toward the sun during the day to create energy and then close their leaves at night to retain moisture. Is this merely a reaction to the presence and absence of sun? No! Turns out, these plants (much like us humans) have an internal clock that functions based on the anticipation of nutrient availability.

If you think about it, the anticipation of nutrient availability concept makes perfect sense. Your brain secretes hormones that help you to get up in the morning, get moving and stay alert. The brain even knows to increase your body temperature! During this time, the body will seek out the nutrients to function. Along the same lines, at night when it is time for sleep, the body anticipates this and slows the body down, lowering body temperature and other functions like kidney and digestion so you won’t have to disrupt your sleep cycle to go to the bathroom. This is the sleep-wake cycle, and it’s been proven that humans can actually die if they are severly sleep-deprived for a week or more.

In a related study, it’s been found that the constant disruption of our circadian rhythm probably causes cancer. Those most at risk are shift workers, frequent travelers (jet lag), new parents, those who are aging and those who have chronic health problems.

So, what part of our brain is responsible for regulating the circadian rhythm? That would be the Suprachiasmatic Nucleus (SCN). A mouthful for such a tiny part of the brain! Dr. Meredith is making great progress with her research and has found that an SCN with a lesion (and therefore no ability to regulate) can be removed and upon transplant of a new SCN (with a slight mutation so they can be sure their findings are correct when measured in the original brain) the cirdacian rhythm is actually restored!

As these studies continue, keep your eye on the pharmaceutical market over the next few years. It’s predicted that this research will help to formulate new medications to aid in sleep disruption and other related ailments.

I’ll leave you with a few interesting facts from the lecture:

1. The most likely time for heart attacks is Monday morning because the body is jerked back from a weekend that differes from the normal M-F routine.

2. Regarding jet lag, for each hour you travel out of your normal time zone, it takes your brain one day to adjust. So, if you traveled six hours ahead, you’d be adjusted in six days.

3. Shift Workers are highly likely to see the negative affects of disrupting the circadian rhythms because of “day” responsibilities such as family and errands and they ultimately don’t get the same quality of sleep.

**Tuesday Talks are held on the first Tuesday of each month and are FREE to the public! For upcoming lecturers, please check our website:

http://www.mdsci.org/events-calendar/events/TuesdayTalks.html

Call 410-545-5940 or email amyers@marylandsciencecenter.org to rsvp for a Tuesday Talks.