Deep in the center of your brain sits the small pineal gland, which produces and secretes the hormone melatonin. This hormone plays in important role in your body's circadian rhythm, the pattern of various biological and mental processes that follow a roughly 24-hour schedule.
The wake-sleep cycle is the most obvious example of your body's circadian rhythms but many other processes follow a daily pattern. Disturbances in your body's internal clock and related derangements in melatonin production and release can potentially affect many aspects of your health -- including your risk for cardiovascular disease and possibly its clinical course.
Melatonin and the Cardiovascular System
Melatonin exerts its effects on your body tissues either directly or by binding to specific receptors, which triggers certain cellular responses. Melatonin receptors occur throughout your cardiovascular system, including on heart muscle and blood vessel cells.
As noted in a July 2016 Journal of Cardiovascular Pharmacology and Therapeutics review article, beneficial effects of naturally occurring melatonin on the cardiovascular system include:
- Reduced blood pressure
- Reduced blood cholesterol
- Increased production of good cholesterol, or HDL
- Reduced formation of the most reactive form of bad cholesterol, or LDL
- Antagonism of fatty arterial blockages, or atherosclerotic plaques
Melatonin and Cardiovascular Disease Risk
The first clue that melatonin levels might affect cardiovascular disease development came from studies which showed an increased risk among shift workers — people who work outside of typical weekday daytime hours.
A seminal article published in April 1999 in the Scandinavian Journal of Work, Environment and Health reviewed results from 17 studies and concluded that shift workers have a 40 percent increased risk for cardiovascular disease compared to day workers.
While many factors contribute to this increased risk, disruption of the normal wake-sleep cycle and an associated reduction in nighttime melatonin release are thought to play a role.
Low melatonin levels are associated with several cardiovascular disease risk factors and conditions, including:
- Elevated total and LDL cholesterol
- Elevated blood sugar
- Increased blood pressure
- Coronary artery disease (CAD), or atherosclerosis of the heart arteries
- Heart attack
- Stroke caused by atherosclerosis
Melatonin, Heart Attack and Cardiac Arrest
Cardiac arrest describes a sudden cessation in heart function. CAD accounts for greater than 60 percent of instances of cardiac arrest, according to the medical website Epocrates. Cardiac arrest caused by CAD occurs when a blockage in the coronary arteries deprives the heart of life-sustaining oxygen. This leads to death of the affected heart tissue, which can lead to a dangerously abnormal heart rhythm and cardiac arrest.
While melatonin levels have not been directly linked to cardiac arrest risk, the association between decreased melatonin and heart disease points to a possible indirect link. Additionally, preliminary research data suggests that administration of medical melatonin might influence the outcome of a heart attack.
Limiting Heart Damage
Based on promising results from animal research, investigators conducted a study, known as the MARIA trial, to determine whether administration of melatonin during a heart attack could potentially limit heart damage.
The August 2017 study report published in the American Journal of Cardiology stated that people who received early administration of melatonin — within approximately 2 to 2.5 hours after the onset of symptoms — experienced less heart damage compared to people who did not receive melatonin.
Administration of melatonin approximately 3 hours or later after the onset of heart attack symptoms, however, was not effective in limiting heart damage. All people in the study underwent balloon angioplasty, a nonsurgical procedure to relieve the coronary artery blockage responsible for triggering a heart attack.
While the results of the MARIA trial are encouraging, additional large-scale research is needed to determine whether there is a role for medicinal melatonin in the immediate aftermath of a heart attack.
Limiting heart damage in the hours following a heart attack can potentially reduce the risk for cardiac arrest due to an abnormal heart rhythm during this period of high vulnerability. Reducing heart damage sustained during a heart attack can also preserve heart function, reduce heart-related disability and potentially prolong an individual's life.
Other Considerations and Precautions
Melatonin is a powerful hormone with wide-reaching effects on the body as a whole and the cardiovascular system in particular. As of the time of publication, there is no definitively established role for medicinal melatonin to prevent or treat cardiovascular disease or cardiac arrest. However, research is ongoing to explore these important issues.
Talk with your healthcare provider if you are considering taking a melatonin supplement to determine whether it is safe for you. As with any over-the-counter supplement, melatonin can potentially interact with medications you are taking or cause side effects, particularly drowsiness.