Simple New Blood Test Reveals Your Body’s Precise Internal Clock to Guide Treatments, Improve Health


Source: Northwestern University

Summary: The first simple blood test to identify your body’s precise internal time clock as compared to the external time has been developed by scientists.


Various groups have tried to get at internal circadian time from a blood test, but nothing has been as accurate or easy. The test, TimeSignature – which requires only two blood draws – can tell physicians and researchers the time in your body despite the time in the external world. For instance, even if it’s 8 a.m. in the external world, it might be 6 a.m. in your body. The first simple blood test to identify your body’s precise internal time clock as compared to the external time has been developed by Northwestern Medicine scientists. This is a much more precise and sophisticated measurement than identifying whether you are a morning lark or a night owl. It can assess a person’s biological clock to within 1.5 hours. Previously, measurements this precise could only be achieved through a costly and laborious process of taking samples every hour over a span of multiple hours. The study findings were published in the journal PNAS.

Circadian rhythm

Credit: CC0 Public Domain

The test measures 40 different gene expression markers in the blood and can be taken any time of day, regardless of whether the patient had a good night’s sleep or was up all night with a baby. It is based on an algorithm developed by Braun and colleagues by drawing subjects’ blood every two hours and examining which genes were higher or lower at certain times of day. Scientists also used gene expression data from studies conducted at four other centers. The scientists then developed a novel machine-learning method that was used to train a computer to predict the time of day based on patterns in these gene expression measurements. Out of about 20,000 genes measured, these 40 emerged with the strongest signal. A link between circadian misalignment and diabetes, obesity, depression, heart disease and asthma has been identified in preclinical research.

Coauthor Dr. Phyllis Zee, chief of sleep medicine in neurology at Feinberg and a Northwestern Medicine neurologist said, “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.”


More Information: Rosemary Braun et al., “Universal method for robust detection of circadian state from gene expression,” PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1800314115


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