Clinician-scientist Phyllis Zee hopes that circadian human biology will become a part of mainstream medicine.

By Lisa Spear

A relatively new branch of medical science called circadian medicine is just beginning to crop up in clinics throughout the country, says Phyllis C. Zee, MD, PhD, who is leading the way in the field.

Around the time of the discovery of the suprachiasmatic nucleus, the part of the brain that controls circadian rhythms, Zee was a graduate student and her interest in circadian biology was only beginning.

As a student at the Chicago Medical School in the early 1980s, she opted to pursue a PhD in circadian science. “No one thought at the time that it would become a field where it would be integrated into sleep medicine and there would be an area called circadian medicine,” Zee says. She would go on to open one of the first circadian medicine clinics in the country, paving the way for others to follow.

Zee was recently recognized for her pioneering work by the National Sleep Foundation (NSF), which gave her the 2021 Lifetime Achievement Award. Zee says she is most proud of her work raising awareness of the importance of the biological clock and its connection to many common ailments, as well as her part in training the next generation of clinicians and scientists.

She works as the director of the Center for Circadian and Sleep Medicine and chief of the Division of Sleep Medicine at Northwestern University’s Feinberg School of Medicine.

As a clinician, Zee says she tries to push the envelope on how to use circadian science to help treat diseases beyond the purely circadian rhythm sleep-wake disorders.

“Circadian medicine is much broader than circadian rhythm disorders. The circadian clock gene regulates rhythmic expression of many other genes, almost all genes, in almost every tissue of your body,” says Zee.

“It will affect the health of almost every tissue of your body, which then means that circadian medicine is relevant to diabetes, it is relevant to muscle disease, it’s relevant to neurological disorders, immunological disorders, skin disorders—It is really broad.”

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Phyllis C. Zee, MD, PhD

Outside of the clinic, her research focuses on understanding the mechanisms that link alterations in sleep, circadian rhythms, and sleep disorders with neurological and cardio-metabolic disorders, as well as the development of treatments for sleep and circadian based disturbances in clinical populations.

“Clearly, circadian sleep-wake disorders are important, but circadian medicine is much broader than that,” Zee explains.

The NSF Lifetime Achievement Award is the organization’s highest honor given to an individual who has proven leadership in the field of sleep health.

Zee says the award is not only a recognition of her work and a great professional honor, but also an acknowledgement of the importance of the circadian clock. 

According to the NSF, basic and clinical studies from Zee’s laboratory have paved the way to novel treatments for disorders associated with sleep and circadian clock dysfunction.

Zee’s current National Institutes of Health-sponsored research includes studies that look at the link between sleep and sleep disorders with metabolic and cardiovascular risk in populations at risk, such as older adults, and the effects of sleep disturbance on adverse pregnancy outcomes.

“Her work to further the understanding of circadian physiology has been pivotal in the field. Beyond the importance of her research, she is a noted educator, mentor, and clinician who has made a significant impact on sleep health and our work at NSF,” says Rick Bogan, MD, board chair of the NSF, in a release.

Sleep Review spoke with Zee about her journey in becoming a clinician-scientist and the future of sleep medicine. The following Q&A has been edited for length and clarity.

Is there any specific research that you have participated in that you are most proud of over the course of your career?

PCZ: It is actually, not a piece of work, or something that I did that I am most proud of, but the trainees, the junior faculty that I have the privilege to support and mentor in my laboratory, as well as the clinicians, the fellows that we have trained and really how they are the ambassadors for the field. Those individuals are carrying on the research, whether it is in sleep or in circadian research. I think [that] is a lot of what makes this ship run.

The other professional accomplishment that I have really wanted to do for a long time is to promote and be able to show that circadian rhythms are applicable to medicine as a whole.

How far are we from having circadian biology incorporated into mainstream medicine?

PCZ: I don’t know; I hope not too long.  The science in circadian biology is just exploding, just growing and growing. Circadian medicine wasn’t even really mentioned until the late ‘80s and it’s really been experimental in the last 8 or so years. I do think there is a lot of momentum.

Lisa Spear is associate editor of Sleep Review.