New test tells you what time it is in your internal clock

Our internal clock is integral to the way our body functions, and when the clock is out of sync or “misaligned” with the outside world, it can create a wide range of problems and increase susceptibility to disease.

Jet lag is perhaps the most famous example of what can happen when the body’s natural circadian rhythms are disrupted through travel across different time zones. Jet lag can cause fatigue, gastrointestinal distress, and make adjusting to new timezones difficult.

But now, researchers from Northwestern University have successfully developed one of the most precise tests to measure an individual’s internal clock compared to external time.

The researcher’s methods and results were published in the journal Proceedings of the National Academy of Sciences.

It’s a simple blood test called TimeSignature that only requires two blood draws but can accurately identify a person’s internal clock within an hour and a half.

For example, it could tell researchers that a person’s internal clock says it’s 6 am whereas it’s actually 8 am in that particular timezone.

“This is a much more precise and sophisticated measurement than identifying whether you are a morning lark or a night owl,” said Rosemary Braun, assistant professor of preventive medicine at Northwestern University Feinberg School of Medicine and lead author of the study.  “We can assess a person’s biological clock to within 1.5 hours.”

Previous tests that measured internal clocks were time-consuming and took a great deal of effort. Individuals had to have blood drawn every hour and the results were not nearly as accurate as TimeSignature.

The test measures 40 different gene expression markers and blood can be drawn at any time of the day regardless of the individual’s sleep patterns. Gene data and an algorithm developed by Braun were used in the development of the test.

The researchers also created a machine-learning method that was able to train a computer to predict the time of day based on the patterns within the 40 gene expression markers.

Because so much of our body’s natural functions and processes are driven by our internal clock and circadian rhythms, the new test could help provide better treatments for people with misaligned internal clocks.

It will also make studying the effects of an out of sync internal clock on heart disease, diabetes, and other diseases much easier.

“Timing is everything,” said Ravi Allada, a co-author of the work. “We know if you have disruption of your internal clock, it can predispose you to a range of diseases. Before we didn’t have a clinically feasible way of assessing the clock in healthy people and people with disease. Now we can see if a disrupted clock correlates with various diseases and, more importantly, if it can predict who is going to get sick.”

Crucially, the test will also be able dictate the optimal times for patients to take certain medications to ensure they are the most effective.

“This is really an integral part of personalized medicine,” said Phyllis Zee, another co-author of the study. “So many drugs have optimal times for dosing. Knowing what time it is in your body is critical to getting the most effective benefits. The best time for you to take the blood pressure drug or the chemotherapy or radiation may be different from somebody else.”
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By Kay Vandette, Earth.com Staff Writer