What Sleep Clock Are You On? Ask Your Skin Cells.

Now, this is fascinating stuff. Researchers just learned that you can look at your skin cell genes to determine whether you are a lark (who likes to get up early), or an owl (who likes to stay up late). A team of German scientists just presented a new study showing that people’s preferences for rising early or late are encoded in their genes, including those found in skin cells.

Other factors also play a role in influencing the time that you like to get up in the morning, but this new finding help us understand the fascinating realm of circadian “clocks” as we continue to explore how the human body deals with the shifts in patterns of activity that are needed to cope with the 24-hour cycle of day and night. Let me explain.

Our internal rhythms repeat roughly every 24 hours. Examples include the sleep-wake cycle, hunger, the ebb and flow of hormones, the rise and fall of body temperature, and other subtle rhythms that mesh with the 24-hour solar day. A lot of people’s sleep problems can be attributed to an internal clock that has become out of sync or mismatched with the day-night cycle. In other words, the individual period length of your body doesn’t sync up with the period length of society’s 24-hour clock.

Everyone’s circadian clock or pacemaker ticks at a different rate. Most people have some idea whether they fall under the lark or owl category, but this latest study further confirms that it’s no urban legend: your sleep-wake schedule is indeed influenced by your own personal circadian clock, and that morning larks have a shorter circadian cycle than night owls.

What’s truly phenomenal is that the scientists here actually could engineer a way to observe and measure individual “clocks” in human skin cells. How? Well, after taking skin samples from volunteers, the scientists inserted into each cell a gene that lights up in ultraviolet light when the cell is metabolically most active. The gene allowed the scientists to follow the circadian rhythm of the cells as they changed over a 24-hour period. In essence, they were able to identify and track skin cells’ built-in timing mechanism set by the central biological clock of the body. This is possible because most cell types have a genetic imprint of a person’s unique circadian physiology.

Science is still trying to understand completely how our body clocks work, and even how many body clocks we have. (For an in-dept look at this topic, refer to my book Beauty Sleep or check out this interactive guide on the National Sleep Foundation’s site.)

Currently, we think we have two body clocks—one that is set by outward cues of light and darkness, and a neurological one that has an internal schedule set in the brain. It is when these two clocks don’t agree on the same schedule and compete with one another that we feel off, for example Jet Lag.

Synchronizing these two clocks come with hitting the “re-set” button every 24 hours. We can do this by exposure to light and by activity. For example, when you want to be alert and awake but your body doesn’t want to follow, you can stimulate your body to re-set itself just by going outside into the sunlight for 10 or 15 minutes or engaging in some physical activity, preferably outside in the bright light.

This latest study will hopefully lead to new tools for diagnosing and treating circadian rhythm disorders such as advanced or delayed sleep-phase syndrome (DSPS). People with DSPS typically cannot fall asleep until well after midnight, nor get up during normal morning hours. And this is a chronic condition—not a one-time problem following a late night. Those who get moody or depressed during long winter months (also called seasonal affected disorder, or SAD) may also benefit from future therapies.

Makes you wonder, though, what other secrets do skin cells hold?