A New Blood Test Reveals the Precise Time of Your Body’s Internal Clock

Doctors will be able to measure a patient’s unique circadian rhythms and determine whether their internal clock is in sync with external time.

We've all been there. | Caiaimage/Tom Merton
We've all been there. | Caiaimage/Tom Merton

You know that laggy feeling when the clock says noon, but your body is telling you midnight? It’s not just in your head. Medical researchers at Northwestern University have developed a new blood test that can determine the precise time of your body’s internal clock.

The new blood test will help doctors and hospital workers make sure that medications are delivered according to your body’s schedule, not the clock on the wall. Details on the patent-pending medical technology are described in the Sept. 10 issue of the journal PNAS.

“This is really an integral part of personalized medicine,” said study co-author and Northwestern Medicine neurologist Dr. Phyllis Zee, in a statement. “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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The test measures 40 different gene expression markers in the blood, and can be taken any time of day.

"Let's see what time you've got on the inside..." | Philippe Turpin/Getty Images

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

Previous methods for reading the body’s circadian clock required multiple blood tests taken every hour throughout the course of the day. The new method uses computer software and mathematical algorithms to get a reading with two sequential blood draws.

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“Circadian timing is a modifiable risk factor for improving cognitive health, but if we can’t measure it, it’s difficult to know if we’ve made the right diagnosis,” Zee said. “Now we can measure it just like a lipid level.”

The software and algorithm will be made available to other researchers for further development, and will also enable them to easily examine the impact of misaligned circadian clocks in a range of maladies, including diabetes and Alzheimer’s disease.