Chronobiology: Definition & Examples

Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Chronobiology studies how natural rhythms affect living organisms. It can help explain why birds migrate, why trees drop their leaves in the fall, and even why some medications should only be taken at night. Learn all about it in this lesson.

When Should You Take Your Medicine?

Darius went to the doctor and found out that he had high cholesterol. His doctor prescribed some medicine for him to take that was supposed to lower his cholesterol levels. Darius took the medicine every morning for three months and then went back to the doctor to see if it was working. When the doctor checked his cholesterol again, it was a little lower, but it seemed like the medicine hadn't had as much of an effect as the doctor hoped it would.

The doctor asked Darius exactly when he had taken the medicine, and when he found out that he'd taken it every morning, he realized what the problem was! ''Why don't you try taking it at night right before you go to bed instead?'' suggested the doctor. Darius wasn't sure why that would matter, but he did what the doctor asked, and three months later, his cholesterol was a lot lower.

Why did the medicine work so much better when he took it at night instead of in the morning? For many years, doctors believed that it didn't really matter WHEN a patient took medicine, but as we are now learning, that isn't entirely true. All people are subject to natural daily rhythms that affect our biology, including our ability to metabolize drugs. It turns out that this is true not just for people, but for almost all living things, and it affects many aspects of biology.

What Is Chronobiology?

Chronobiology is the branch of biology that studies the natural physiological rhythms of organisms, including people. One example of a type of natural cycle that is studied by chronobiologists is the circadian rhythm that governs our sleep schedule. Most people are awake during the daytime hours and asleep during the nighttime hours. This pattern develops early on in life and is remarkably difficult to change. Chronobiological research has shown that people who work at night and sleep during the day suffer from chronic health conditions at much higher rates than people who maintain a more typical circadian rhythm.

Many natural rhythms are affected by the daily cycle set by the sun.
Many natural rhythms are affected by the daily cycle set by the Sun

Chronobiology and Pharmacology

Chronobiology also affects when people, like Darius, should take certain medications. Darius's medication was supposed to lower his cholesterol by inhibiting the amount of cholesterol produced by his liver. It turns out that the liver produces most of its cholesterol during the night rather than the daytime. Therefore, the medication is much more effective when it is taken at night instead of in the morning. Many medications work this way, and their effectiveness can be strongly affected by WHEN the medication is administered.

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