In 2017, the Nobel Prize in Physiology or Medicine was awarded to three scientists who study how the human body clock works. This recognition was due to their groundbreaking research, of course, but it was also an acknowledgement of the growing importance of understanding our circadian rhythms. They have a far greater effect on our health than simply jet-lag; our internal timekeepers regulate hormones, body temperatures, hunger and metabolic processes.

"There's a ton of evidence showing that conditions like depression, diabetes, heart disease and Alzheimer's have a connection to your body clock," Rosemary Braun, assistant professor of preventive medicine at Northwestern University's Feinberg School of Medicine, told Smithsonian. "So, what if we could detect a person's physiological time?"

Scientists have recently discovered just that. A new study published in the Proceedings of the National Academy of Sciences details how a blood test called TimeSignature can show a person's biological time within a 90-minute window. This information has immediate import — doctors can be much more precise about when they administer drugs. By giving them at the right time for the body's natural cycles, lower doses of medicine can be used to get the same effect, and side-effects can be minimized.

It starts with chronotype

Each person's internal clock runs on a different schedule. The most obvious manifestation of that is that some people are early birds, while others are night owls (and some are in-between). This difference is called chronotype, and it's a genetically based difference between people. While schedules are often inflexible in the modern world, it behooved our ancestors' hunter-gatherer societies to have some people rise early and some people stay up late. It made sense for someone in the group to be awake at all times — for protection from predators or other marauding tribes, for hunting opportunities, or to keep an eye on the weather or the tides. There are myriad reasons it doesn't make sense in that milieu to have everyone asleep at the same time.

So, people with different chronotypes have different metabolic responses at different times of the day, and that can affect how well medicine works. Doctors have known this for some time, but they could only know a person's internal clock by taking blood samples every few hours and comparing them to each other, which was expensive and impractical (not to mention uncomfortable for the patient who was likely dealing with other issues).

TimeSignature uses artificial intelligence — and just two blood samples — to do the same thing. It works by analyzing 41 genes from the blood sample, and finding patterns by looking at when certain proteins are created. Time of day can be extrapolated backwards from what's known about when those proteins are typically created.

Right now, the application has proven to work only in the healthy human subjects first tested to establish baselines. TimeSignature can now reliably match up a person's body rhythm with the clock, so next it needs to be tested more in a variety of subjects. Baselines also need to be established to understand what's normal and what kind of "off" body clocks might be connected to diseases. In addition to medications being administered at the right times, this application of the technology could be another way to use this information in a health care setting. It may also answer the question of why those who ignore their clocks (shift workers and frequent time zone-crossing travelers), suffer from higher incidences of a variety of health issues.

"If someone's body time is way off from what it should be, that may be a predisposing risk factor for a disease," Ravi Allada, a professor of neurobiology at Northwestern's Weinberg College of Arts and Sciences told Smithsonian. "The major advance here is being able to measure a biological process that we know is important when it comes to diseases, and do it in a way that's practical, that someone can go into their doctor's office and get their blood drawn and figure this out."

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.

Blood test can pinpoint your body clock — and use it for good
A new blood test could determine your personal circadian rhythm, which can help make medicines more effective.