New test to determine if your internal clock and alarm clock are out of sync

A new blood test can help determine what time a person's body thinks it is—independent of the actual time of day—which has enormous implications for improved health and wellbeing.

Of reported sleep disturbances, anywhere from seven to 16 per cent of North American adolescents, and slightly fewer adults, have what's called Delayed Sleep Phase Disorder, meaning they have trouble going to sleep and getting up.

The most challenging part of studying these disorders is figuring out what time it is in the body. Previous methods required multiple hourly blood draws over several hours to try to measure the amount of melatonin in the body.

The new TimeSignature test, developed by Northwestern University and published this week in the Proceedings of the National Academy of Sciences, is a simple blood test requiring only two blood draws a few hours apart.

"This will enable researchers to start to incorporate measures of circadian rhythms into their research," said Rosemary Braun, lead author on the paper.

"Before, serial sampling of melatonin was just really burdensome. You needed to have your patients in the lab for many hours, which made it unfeasible for researchers to look at the lengths between the clock and all of these adverse outcomes."

How do internal clocks work?

A cellular clock is an intrinsic process that controls almost all cells in the body and affects different processes in the body.

The master clock genes work through the hypothalamus in the brain, a tiny little region right between the eyes that acts as the puppet master of the sleep-wake cycle. From there a hormone called melatonin is produced and that's what makes people sleepy at night.

The clock also controls more than just when a person is alert or tired. It also controls sleep, digestion, blood pressure and body temperature. All of these things change over the course of a day at the level of our genes.

Researchers from Northwestern University measured 20,000 different genes in the blood every two hours in their patients. They combined the results with data from several other studies with similar measurements and developed an algorithm to identify a small set of markers that were the most reliable indicators of time.

From that, the computer came up with 40 gene markers that are differentially expressed (or turned on differently) depending on the time of day.

Improved treatment for chronic health conditions

A misalignment of the circadian rhythm can predispose people to heart disease, obesity, Alzheimer's, diabetes and other chronic health problems. The issue is separate from getting enough sleep and is due to a physiological lack of synchronicity between the internal and external clocks.

This discovery will help doctors to better diagnose and treat people with chronic sleep phase disturbances and could go even improve the efficacy of drug delivery.

"There's increasing evidence that different drugs have different optimal timings for deliveries. But, to date, it's been very difficult to develop good chronotherapeutics because it's been so difficult to measure the time of day in a person's body," said Braun.

The researchers hope that will now change with this simple blood test that can help to address an issue that was simply too cumbersome to investigate before.