Cafe Scientifique: Early Birds and Night Owls

Last weekend, chronobiologist Till Roenneberg gave a free lecture for the public at The Mind Museum on body clocks, chronotypes, and their relation to health. Dr. Roenneberg is also the scientific advisor of PhilSHIFT, a research program that studies Filipino body clocks.

After a brief introduction, Dr. Roennberg began by asking the audience how many drank coffee. Many revealed themselves to be fond of, and even dependent on coffee, so that they can stay awake and go to work or school. 

However, if we were to base our sleeping schedules only on how much sleep our bodies craved, unfettered by external factors like deadlines, then we'd likely be sleeping at different times. This is controlled by our body clock. The body clock, Dr. Roenneberg states, is different from the clocks that our lives revolve around.

The reason we drink so much coffee, he adds, is because our body clocks have shifted later. Since many of us spend so little time outside per day, we don't get enough exposure to light. For our body clocks to be set correctly, they need real light, and real darkness.

The human species is active during the day, with our sight being our predominant sense. During the night, we depend on artificial light to function. This dependence on artificial light means we no longer get the right signals for our body clocks.

Unfortunately, we cannot stop working during the night - our workloads require us to work around the clock, and to wake up early every morning (at least, for most kinds of shifts). In addition, the mere fact that you need an alarm to rouse you in the morning means that you were not able to sleep to the end of your biological sleep cycle for that night.

Dr. Roenneberg goes on to explain the concept of a chronotype: early chronotypes are early birds; they go to bed early, and also wake up early. Late chronotypes, on the other hand, are night owls. They sleep late, and hence, also wake up later. While the late chronotype is often associated with being "lazy", there are several factors which influence your chronotype, such as genetics, age, and sex.

From childhood on, we begin as early chronotypes. Puberty and adolescence cause a shift to a later chronotype. Young women generally shift to an earlier chronotype at age 19, while men shift to an earlier chronotype at age 22. In effect, many people in the age range of 18-22 years are late chronotypes, but are still asked to go to school very early; even earlier than the times many companies require of their employees to go to work!

This often leads to situations where late chronotypes compensate for the lost sleep (or "sleep debt") on their days off, causing a chronic misalignment in their sleep schedules. This is known as social jet lag,which increases one's risk of heart disease and diabetes.

Dr. Roenneberg acknowledges social jet lag as a real problem. "If a person wants to go to work at 10 AM instead of 8, it doesn't make him or her lazy!" On the contrary, it's because they want to be more productive with their time, and will also be less likely to take sick days.

The quick lecture was followed by a lively question and answer session with the audience. One parent asked how much sleep her three-year old son should have. Dr. Roenneberg replied, "while you can overfeed your child, you can't oversleep them." Three-year olds need more sleep than adults or adolescents, (with toddlers needing around 11-13 hours, and adults needing around 7-9) and this is crucial for the proper development of their brains. 

Another question involved how sleep quality could be improved. "If you wake up and don't feel refreshed, this is bad quality sleep," replied Dr. Roenneberg. You must sleep when your own body clock allows you to sleep. To help you fall asleep, you can also avoid looking at blue light (such as those from cellphones or computer screens) during the evening.

In response to a question on why we sleep at all, Dr. Roenneberg said it was like asking why we eat. There are many different functions that sleep serves, with repair being one of them. Your immune system also benefits from sleep, as you're more likely to come down with a cold if you are exposed to the virus. 

Because of how important sleep is, we cannot avoid or do away with sleep, even if we'd like to, in our rush to meet deadlines. Sleep allows us to enjoy our day, and makes us productive. We also should not be forcing ourselves to stay awake for very long. How long we can stay awake before it gets dangerous depends on what we do. 

Certainly, even a relatively short amount of time without sleep would be dangerous if you were doing anything that needed dexterity or focus. Staying awake for longer than 16 hours is possible, but will sacrifice your social competence and decision-making ability.

The reason we ask ourselves these questions, he says, is because modern society considers sleep as a waste of time, when it isn't. Without rest, we become less efficient. By setting aside enough time for good quality sleep every day, we can avoid the side effects that come with long-term sleep deprivation. 

Saturday's Cafe Scientifique was a wonderful opportunity for audiences of all ages to learn about the intricacies of our sleep cycles, why sleep is important, and how this affects our health.

If you enjoyed learning about the Cafe Scientifique and would like to answer the researchers' questionnaire, you can help contribute to science at this link: PhilSHIFT survey.

Cafe Scientifique is a world-wide movement that aims to bring science closer to the public through conversations with scientists, artists and thinkers. This is a FREE event. If you have a science topic you'd like us to discuss, please email us at

To learn more about The Mind Museum's exhibitions as well as upcoming and regular activities, visit the museum's website, and follow the museum on Facebook, Twitter, and Instagram!

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