Blood Test Can Predict Your Internal Clock, Improve Treatment

A new blood test can determine what time it is inside your body.

Researchers at Northwestern University found that certain genes are expressed based on what time a person's internal clock thinks it is. Published in PNAS on Monday, the study showed how the test might help with both diagnosing issues and treating them.

Called TimeSignature, the blood test utilizes a machine-learning algorithm. It can test for different patterns of gene expression based on the time of day. Of the 20,000 genes the team examined, around 40 were showing gene signals at certain times. Those genes were more likely to turn on at a specific point in the day, but it varied based on a person's internal clock.

At 12 p.m., for example, the body might express gene A and gene B. Then at 6 p.m., it might express gene B but also gene C. When scientists use the TimeSignature test on someone, they can determine what time the body thinks it is.

The scientists were able to test the process on 11 patients. For the test to be accurate, they did two blood draws from each patient that were spaced apart. When they tested the patients' blood, they were able to narrow down what time the blood was drawn down to two hours. The test can be beneficial in a few different ways. If someone's body is expressing that it's a time of day that it's not, for example, it's expressing genes A and B as if it's noon, but it's actually 6 p.m., doctors would know there's a problem with the internal clock.

"Timing is everything," study co-author Ravi Allada, a professor of neurobiology at Northwestern University, said in a statement "We know if you have disruption of your internal clock, it can predispose you to a range of diseases. Virtually every tissue and organ system are governed by circadian rhythm."

Old Gold Watch
A British watchmaker holds a 1697 watch. Misalignment of the internal clock has been linked to chronic diseases, as well as heart disease, obesity, substance abuse, cancer and diabetes. JACK TAYLOR/GETTY IMAGES

A misalignment can cause many health issues because it can lead to inflammation, as well as a reduction in insulin. Misalignment has also been linked to chronic diseases, as well as heart disease, obesity, substance abuse, cancer and diabetes. TimeSignature could also help doctors determine the best treatment for a patient.

"This is really an integral part of personalized medicine. So many drugs have optimal times for dosing," Dr. Phyllis Zee, a co-author on the study, the chief of sleep medicine in neurology at Northwestern University and a Northwestern Medicine neurologist, said in a statement. "The best time for you to take the blood pressure drug or the chemotherapy or radiation may be different from somebody else."