Circadian rhythms, derived from the Latin phrase meaning "about a day," regulate various biological processes, including sleep-wake cycles and heart function. These rhythms are maintained by a master clock in the brain that coordinates internal clocks within tissues and organs, such as the heart. While these biological clocks are attuned to the daily light-dark cycle, they are also influenced by factors like sleep patterns, diet, exercise, and stress.
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A comprehensive review published on July 15, 2025, in the European Heart Journal discusses how disruptions in circadian rhythms—due to shift work, insufficient sleep, or unhealthy lifestyles—can elevate the risk of cardiovascular disease. Dr. Frank A.J.L. Scheer, who leads the Medical Chronobiology Program at Brigham and Women's Hospital, emphasizes that misalignment between sleep, dietary, and exercise patterns relative to circadian rhythms can trigger physiological changes linked to increased heart risk.
Heart attacks show a distinct pattern, being approximately three times more likely to occur in the morning rather than in the evening. Dr. Scheer’s research has identified that a protein responsible for blood clotting peaks around 6:30 a.m., contributing to this risk. Furthermore, heart attacks occurring during the early morning hours tend to cause more significant damage to heart tissue and worse long-term outcomes.
Mondays are particularly precarious for heart attacks, likely due to the phenomenon known as "social jet lag." People generally alter their sleep schedules on weekends, leading to misalignments when they return to early work hours on Mondays. This adjustment results in changes in blood pressure and metabolism, heightening the risk for a heart attack. A similar risk increase is observed shortly after the spring daylight saving time adjustment.
Research indicates that night shift workers have elevated rates of cardiovascular disease, largely attributed to circadian misalignment. A study published in Nature Communications on April 8, 2025, suggests that eating primarily during daylight hours may mitigate these risks for shift workers. Late-night meals can raise hunger hormones and slow metabolism, potentially linking them to obesity.
While conventional wisdom advises against evening exercise due to concerns about sleep disruption, evidence points to afternoon and evening workouts lowering blood pressure and cholesterol more effectively than morning sessions. Dr. Scheer notes that, generally, earlier meals are advantageous, while later exercise may yield heart health benefits.
The review also explores chronotherapy, which aligns medication schedules with the body's natural rhythms. For instance, some short-acting statins, like simvastatin and pravastatin, are often prescribed for nighttime use to coincide with cholesterol production peaks. However, with stronger statins like rosuvastatin, timing has less impact, and taking blood pressure medications at bedtime may reduce dangerous early-morning surges.
To align with your internal clock and promote heart health, consider the following practices: consume most calories in the morning when metabolism is more efficient, exercise in the afternoon or evening, get sunlight exposure early in the day, maintain a consistent sleep schedule, limit evening screen time, and consult your doctor about the timing of medications.