Your body's circadian rhythm does much more than tell you when to sleep. This internal 24-hour clock plays a crucial role in heart and metabolic health. According to a recent scientific statement from the American Heart Association (AHA), disruptions to this rhythm — such as staying up late to cram for an exam, eating late night meals, even exercising in the evening — could significantly increase the risk of serious health conditions.
"For many years, we've known there is a link between sleep quality and cardiovascular health," said Dr. Harneet Walia, professor at the Herbert Wertheim College of Medicine and medical director of sleep medicine at Baptist Health Miami Cardiac & Vascular Institute.
"Now there is a growing body of evidence showing that disruptions in circadian rhythm play a role in the development of obesity, Type 2 diabetes and high blood pressure, as well as cardiovascular disease."
Understanding circadian rhythm
The body's natural clock orchestrates when biological processes happen, regulating hormone release, digestion, body temperature, blood pressure and metabolism throughout the day and night.
The precise timing is not just convenient, it's essential for health. When biological processes occur at the right time, they work efficiently. When they are thrown off schedule, problems can emerge. That's why chronotype — whether someone is naturally a morning person or a night owl — matters, especially for students whose class schedules and late-night studying with prolonged exposure to computer screens often conflict with internal clock preferences. Similar challenges affect people who work overnight or rotating shifts, where job demands regularly run counter to natural sleep–wake patterns.
The AHA scientific statement, "Role of Circadian Health in Cardiometabolic Health and Disease Risk," notes that when people do things (sleep, eat, exercise) may be just as important as what they do for heart health.
"It's shifting the conversation from simply eating healthy, getting a good night's sleep and exercising to also maintaining consistent daily routines for optimal health," said Walia.
Key takeaways
The AHA scientific statement, authored by experts in cardiovascular research, sleep medicine, public health, nutrition science and environmental health, outlines factors that can disrupt your circadian rhythm, including:
- Inconsistent sleep or an irregular sleep schedule. Poor sleep can increase C-reactive protein, a marker of inflammation, as well as cortisol, a stress hormone. Both are contributors to atherosclerosis, a leading cause of cardiovascular disease.
- Eating late at night. Late meals can affect metabolic health beyond calorie content, potentially leading to weight gain and blood sugar spikes. The statement notes that rodent studies show feeding during the inactive period leads to greater weight gain despite similar food intake.
- Exercising in the evening rather than in the morning or afternoon. The statement describes timed physical activity as a nonpharmacologic strategy that can improve circadian health by optimizing sleep quality, enhancing daytime alertness, and supporting cardiometabolic outcomes.
- Using artificial nighttime light, particularly from screens. Several studies cited in the statement found that morning light exposure is associated with lower body fat, mass, and appetite.
Strategies to protect your body clock
Walia agrees with the authors of the AHA statement that more research is needed to develop personalized recommendations. However, she said the evidence is clear: The body's internal clock plays an important role in heart health, and maintaining consistent sleep schedules, appropriate light exposure, well-timed meals and regular exercise routines can help reduce the risk of serious health conditions.
