Blood Test Could Tell You What Time It Is In Your Body

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Whether you're an early bird, a night owl or a functions-best-at-midday kind of person very much has to do with slight variations in your body's internal clock. But if you're unclear on what time it is inside your body, there might be a blood test one day that can tell you.

That could be important, because a "misalignment" between your body's clock and the actual time can be harmful. (An example of such a misalignment would be if the most accurate atomic clock says it's 8 p.m., while the cells inside a person's body said, no, it's 6 p.m.)

The test could also help doctors deliver drug doses at precise times, the researchers said, though more research is needed before the test could be used clinically.

The new blood test, called TimeSignature, uses a machine-learning algorithm that's trained to look for patterns of gene expression at different times of day. The researchers recently filed a patent for the blood test and published the results of their study today (Sept. 10) in the journal PNAS.

The team examined 20,000 genes in the body and found that there were around 40 that showed robust gene signals connected to different times. In other words, these 40 genes were more likely to turn on at certain times of day, based on a person's internal clock. [Genetics by the Numbers: 10 Tantalizing Tales]

For example, if a person's body thinks it's 6 a.m., it will express more of gene A than gene B; whereas if it thinks it is 8 a.m., perhaps it will express more of gene C and a little bit of genes A and B. The TimeSignature test learns those patterns and can spit out an estimate of what time the body's clock thinks it is.

The researchers tested the TimeSignature algorithm on genetic data from three separate studies that were focused on blood and also tried the test on blood samples from 11 patients. They found that they could predict when the blood was drawn, typically within a range of 2 hours. They also reported that once their test is trained on what levels of genes to expect, it can be universally applied to data from various patients. 

In order for the test to be accurate, the patient would need to have at least two blood draws that are reasonably spaced apart in time, according to the study. In contrast, previous tests that aimed to pinpoint the time of the internal clock required blood draws every hour over multiple hours, the researchers said.

Such a test might be able to help medical practitioners deliver drugs at times that are tailored for each individual patient.

"So many drugs have optimal times for dosing," study co-author Dr. Phyllis Zee, the chief of sleep medicine in neurology at Northwestern University Feinberg School of Medicine 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."

In addition, almost every cell in the body can tell time — and many dictate processes in the body based on what time it is (for example, if it's bedtime, cells might release the sleep hormone melatonin).

Disruptions in circadian rhythm have been associated with a variety of conditions such as diabetes, obesity, heart disease and asthma, according to the statement, and the test might be able to improve the diagnosis of such disorders and predict who might get sick.

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

"Timing is everything," Allada said.

Originally published on Live Science.

Yasemin Saplakoglu
Staff Writer

Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.