How To Reset Your Circadian Rhythm

Circadian rhythm, our internal biological 24-hour cycle, regulates many of the body’s critical functions. When this internal clock is in tune with the outside world, our body knows when to sleep and when to wake.

“It’s a stabilizing force in the body that coordinates almost everything,” explains Melissa Knauert, MD, PhD, associate professor of medicine (pulmonary, critical care and sleep medicine) at Yale School of Medicine (YSM), who researches circadian disruption in the ICU. “Every cell has a clock, and the brain has a central clock.”

Cues from the environment, such as light, are taken in as information and processed by the body’s circadian system to reinforce this daily rhythm, Knauert adds. Our body is optimized to eat, move, and sleep at certain times.

For example, circadian night is the biological opportunity—or optimal time—to sleep the best and longest, Knauert says, and circadian day is the biological opportunity to digest food. Different organ systems are designed to function at different times.

A strong and regular circadian rhythm leads to more than better sleep, echoes Brienne Miner, MD, MHS, assistant professor of medicine (geriatrics) at YSM, who investigates sleep deficiency in older adults. “It turns out that it has been linked to other important outcomes, like cognition and mortality,” she says.

But certain environmental and lifestyle factors—such as work schedules, travel, stress, and even the transition to Daylight Saving Time, in March, when our clocks “spring forward”—can disrupt this natural cycle, adversely affecting our physical and mental health.

“Daylight, exercise, social activity, meal timing, and a regular sleep-wake schedule allow us to keep a normal rhythm,” Miner says. “So any changes to these behaviors or lack of these cues from the environment can disrupt the circadian rhythm.”

One of the main ways to keep this rhythm on track is to be active during the day rather than sedentary and staying at home, adds Miner, whose work focuses on improving sleep-related symptoms in older adults. “Getting out of the house is a multimodal intervention, as it gets you exposed to light, and social and physical activity,” she says.

Knauert emphasizes the importance of getting sunlight in the morning—especially the first few days after transitioning to Daylight Saving Time—and avoiding bright lights or late meals in the evening.

“The circadian system is like a biological road map that we can follow to improve sleep and many aspects of our health,” says Knauert, whose research on sleep and circadian disruption in critically ill patients has shown that cues such as day and night lighting levels can impact the length of time a patient will remain in the hospital.

“There’s even data emerging about optimal times to receive chemotherapy treatment, take medicine, and get vaccinated,” Knauert says. “Better understanding this new frontier has the potential to fundamentally improve health in a very broad way.”

The Department of Internal Medicine at Yale School of Medicine is among the nation's premier departments, bringing together an elite cadre of clinicians, investigators, educators, and staff in one of the world's top medical schools. To learn more, visit Internal Medicine.