Are you a night owl or the early bird who always gets the worm? Two recent studies examine the importance of our circadian rhythms and what they could mean for treating certain diseases
In a paper published in the Lancet Neurology this week, Australian scientists discovered a link between the timing of epileptic seizures and natural circadian rhythms. Meanwhile, researchers at Northwestern University in Chicago say they developed a blood test identifying the precise time of our body's internal clock that monitors functions such as our sleep/wake cycle.
The studies are part of a growing field called circadian medicine.
Our sleep cycle, blood pressure, temperature and other bodily functions are regulated by thousands of clocks within our cells. Synchronized from a region of the brain called the superchiasmatic nucleus or SCN, our circadian rhythms help us adapt to light and dark and tell us when to be be active and awake and when we need to rest and sleep.
For centuries, scientists have understood that all life had these internal clocks, but they couldn't figure out what made them tick. That changed last year when the Nobel Prize in Medicine was awarded to Jeffrey C. Hall, Michael Rosbash and Michael W. Young for their work in discovering the molecular mechanisms that control circadian rhythms.
Our biological clock helps to regulate sleep patterns, feeding behavior, hormone release and blood pressure <a href="https://twitter.com/hashtag/NobelPrize?src=hash&ref_src=twsrc%5Etfw">#NobelPrize</a> <a href="https://t.co/NgL7761AFE">pic.twitter.com/NgL7761AFE</a>
The prize propelled circadian medicine into orbit. Researchers around the world are now using this information to understand what happens when our clocks go wonky and how that could play a role in illnesses like diabetes, obesity, heart disease, and others.
Australian professor Mark Cook and his team followed over 1,000 patients suffering from epilepsy, using a phone app called Seizure Tracker. About 80 per cent of them recorded circadian rhythms associated with their seizures. In most cases, the seizures occurred between 8 a.m and 8 p.m. The researchers were even able to pinpoint, with some success, the days when most seizures would occur: Tuesdays and Wednesdays.
Men have monthly cycles, too
"We were surprised to see that patients had so many different rhythms in the patterns of seizures," said Cook, who's in the medicine department at the University of Melbourne. "Many had cycles of less than 24 hours, most had a cycle of 24 hours, and about a quarter of them had a very strong weekly cycle," meaning they knew which day they would likely have a seizure.
"A big surprise was that men had monthly cycles as often as women, and though this has been attributed in the past to menstrual cycles, clearly this can't be the explanation."
Cook believes this information can help doctors manage epilepsy better, by improving the forecasting of their seizures. But it could also give them a way to zero in on the best time of day patients should be taking their meds — a field of research known as chronotherapeutics.
You can start to target the body clock and come up with new, innovative ways to treat disease.– Prof. Tami Martino
In Chicago, Rosemary Braun, assistant professor of preventive medicine at Northwestern University's Feinberg School of Medicine, has been trying to determine our body's optimal time, regardless of what any external clock may read. And her team may have found a way to measure that. Their results were also published this week in the journal PNAS.
Called TimeSignature, it requires two blood samples taken a few hours apart. Using an algorithm, researchers were able to measure 40 markers in the blood that had the strongest signal.
Braun, the paper's lead author, said TimeSignature can assess a person's biological clock to within 90 minutes. The potential, she said, is big.
It's time to take your medicine
"Your doctor will be able to use it to say, 'Here's not only what time is it in your body, but also we would be able to predict you have such-and-such risk of disease and this is the best time to be taking your medicine.'"
These studies are really exciting, said Prof. Tami Martino, director of the Centre for Cardiovascular Investigations at the University of Guelph. Understanding the science of body time, she said, can lead to innovations in clinical medicines that could benefit people.
Her own work is showing that. Martino has looked at how male and female hearts respond to time-of-day signals. It turns out hormones play a role in the circadian clock, and women's hormones give their hearts more resilience, at least until they're older. That may provide them more protection against heart disease.
Martino believes circadian medicine is just beginning, and it can unlock the inner workings of our bodies that have mystified scientists for centuries.
"On one hand you don't even have to invent new therapies, you can just improve their efficacy by applying circadian biology," she said.
"On the other hand, it's opening up a whole new field of pharmacology and applications where you can start to target the body clock and come up with new, innovative ways to treat disease and new avenues that we didn't have available before."
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