Circadian rhythm plays a fundamental role cardiometabolic health

...but too many Americans do things to undermine their body’s natural cycles, according to a new scientific statement from the American Heart Association.

“The statement urges basic scientists and clinicians to understand how the role of light timing, sleep timing and duration, timing of meal intake, and exercise timing can have substantial effects on cardiometabolic health,” said Diana Martinez, PhD, assistant professor of biomedical sciences at Cooper Medical School of Rowan University in Camden, New Jersey, who was not involved in writing the statement.

The following document was published recently in Circulation:

‘A Modern Epidemic’

Dayna A. Johnson, PhD, MPH, MSW, MS, distinguished associate professor at Rollins School of Public Health at Emory University in Atlanta and vice chair of the writing committee for the statement, said the evidence for a link between circadian health and cardiometabolic risk has become increasingly strong.

“Over the past decade, we’ve accumulated compelling research showing that our body’s 24-hour biological clock fundamentally regulates heart health, blood pressure, metabolism, and more,” Johnson told Medscape Medical News.

Artificial light at night, late-night eating, and irregular schedules lead to circadian disruption, which has become “a modern epidemic,” according to Johnson.

“These are all modifiable behaviors,” she said. “We have enough evidence to give the population, including clinicians, clear actionable guidance on improving circadian health to reduce heart disease risk.”

The statement cites light exposure, sleep-wake patterns, food intake timing, and exercise as factors that affect the circadian system and provides a list of seven “take-home pearls” for clinicians. These tips include evidence-backed statements such as “sleep timing regularity is as important as sleep duration” and “light exposure timing is a therapeutic tool, but its effect depends on its timing relative to a person’s internal clock.”

“The timing of behaviors matter,” Johnson stressed. “It’s not just about eating healthy or exercising. Eating the same meal at night vs in the morning has different effects on your metabolism because your body clock changes how you process food throughout the day.”

The authors also describe how disruptions in circadian rhythm may increase the risk for obesity and weight gain, type 2 diabetes, hypertension, and cardiovascular disease. Circadian misalignment also can exacerbate disparities in cardiometabolic health, which could affect those from low-resource areas who may have to work nontraditional hours, such as shift workers, the authors noted. The rotating schedule of shift workers exposes them to different timing of light, having meals at different times, and not having the opportunity to exercise, Martinez said.

“We have to realize as a society that we’re putting some of our most needed workers at risk due to our lifestyle,” she said.

To counter circadian disruption, Johnson recommended a variety of “simple strategies,” such as keeping consistent sleep-wake times, getting morning sunlight, eating earlier in the day, and maintaining regular mealtimes. Johnson also suggested avoiding bright light at night, such as from electronic devices, which, the authors wrote, could adversely affect the central circadian clock while making it more difficult to fall asleep. “These are practical interventions that don't require medications or expensive equipment,” she said.

Timing: More Than Just Behavior

Martinez recommended cardiologists consider sleep and circadian disruptions when evaluating patients. “The timing of when they eat or exercise should be considered as much as if they eat healthy or exercise,” she said. “Patients, I believe, take these small behaviors for granted. Healthy habits include timing and should be considered when discussing patients’ sleep, exercise, eating, and light exposure.”

“Timing is biology, not just behavior,” Johnson added. “Also, individual differences matter. Some people are natural ‘morning larks,’ others are ‘night owls.’ Forcing someone’s schedule too far from their natural rhythm can have negative consequences and create circadian disruption. It is important to understand a patient’s chronotype.”

Johnson and Martinez reported having no relevant financial relationships.

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Written by Brian Ellis, a freelance writer and editor who lives in Southwest Virginia. Originally published on October 31, 2025 in