Pitt researchers highlight the health benefits of rising early

Being an early bird or a night owl may be defined by your genetics, but Pitt research published March 16 in The Journal of Physiology suggests that those who rise early may receive some protection against conditions such as type 2 diabetes in return.

Getting up between 4:30 and 6 a.m. for rowing practice and competitions has been routine since eighth grade for Zachary Chan, a Fox Chapel Area High School junior and the study’s lead author. But when Chan, 17, found himself waking up early on days that he didn’t have to, he had a couple of questions: “Is getting up this early affecting my health at all? And, if it is affecting my health, how?”

So, he set out to answer those questions with Neil Kelly, assistant professor of medicine, University of Pittsburgh, School of Medicine, as a mentor.

Everyone has a genetically predetermined preference for the time of the day they are most productive, called a chronotype, which is often split into the well-known categories of being an early bird or a night owl.

“The relationship that we wanted to focus on was chronotype and risk of certain diseases,” says Chan. Previous research, he adds, suggests that chronotype affects your disease risk through shifting your circadian rhythm.

Unlike chronotype, circadian rhythm—the daily oscillation pattern of a person’s 24-hour day—is changeable. However, tracking an individual’s circadian rhythm, Kelly notes, has been a notoriously burdensome task that can require serial blood draws to measure changes in hormone levels. So, to answer their research question, Chan and Kelly had to find an alternative way to track circadian rhythm by identifying an easy measurement that accurately reflects a person’s circadian rhythm.

Leveraging wearable device data available in the All of Us cohort—a large National Institutes of Health research program using participant health data to accelerate medical discovery—they found that the phase of people’s heart rates over 24 hours aligns well with their circadian rhythms: “Looking at just the phase of your rhythm could actually tell us whether you track more with a morning rhythm or an evening rhythm. And we actually saw that lined up very nicely with genetic variants that are known to be associated with chronotype,” says Kelly.

Chan and Kelly’s research team then assessed disease risk across more than 3,000 conditions as a function of heart rate phase (HRP) and identified 22 phenome-wide significant associations. Their findings were also consistent with prior chronotype associations, validating that HRP is a clinically meaningful and scalable indicator. They also observed that phase delays in HRP, consistent with a night owl chronotype, were associated with an increased risk of metabolic, addiction and mood disorders. Additionally, one “morningness” variant (rs1144666(T)) was particularly associated with a reduced risk for type 2 diabetes.

While having an evening circadian rhythm is associated with increased risk for diabetes and other diseases, says Kelly, he notes that other studies show that those rhythms can be shifted based on different behaviors, such as waking up early—even if one doesn't innately want to—and exercising in the morning. While “it’s premature to say that morning exercise would shift your heart rate phase in a protective way,” he says, he does say that the evidence supports that staying up too late and postponing activities too late in the day is associated with negative health consequences.

“I’m encouraging myself to try to change my behaviors based on what we’re finding here. Nobody can guarantee a specific outcome, but I think there seems to be a clear benefit to being more of a morning person if you have the ability to do that,” says Kelly.

Their next step is to begin testing these genomic variants in the lab to identify how their effects on circadian rhythm can control health outcomes at a biological level. Additionally, a big next step is to test, through prospective studies, whether targeted interventions can intentionally shift circadian rhythms and if those shifts beneficially affect health outcomes.

“I think sleep is an underrated aspect of our health, especially for high school students,” says Chan. “But for rowing, I feel like I’ve become more of a morning person because I’ve had to do this for multiple years consistently—I think what excited me is that it’s good for my health.”

Additional Pitt School of Medicine faculty involved in the project include Colleen McClung, professor of psychiatry, and Seyed Mehdi Nouraie, associate professor of medicine.