Individuals that work in shifts at night have a higher incidence of heart disease. This risk has been linked to the body's production of the hormone melatonin. Commonly referred to as the "sleep hormone" that controls the body's circadian rhythm, melatonin can also effect other areas such as aging, immune health, reproductive cycles and cardiovascular health.
Melatonin is commonly known as the "sleep hormone" because it helps to maintain the body's circadian rhythm, your sleep-wake cycle. This means melatonin plays a key role in when you fall asleep and when you wake up. It is secreted by the pineal gland in the brain and also works to regulate other hormones.
Your body produces more melatonin when it is dark, while production drops when it is light. For this reason, staying up late or being exposed to bright lights in the evening or too little light during the day can disrupt the body's normal production of melatonin. The University of Maryland Medical Center notes that jet lag, shift work and even poor vision can cause disruptive sleep patterns by causing an imbalance in melatonin cycles.
In addition to regulating the body's circadian rhythm, melatonin also helps to control the release of female reproductive hormones that determine the menstrual cycle. This determines when a woman has her period and when menstruation ceases in menopause. According to the University of Maryland Medical Center, melatonin may also be linked to aging because as we age this hormone level drops. Children have the highest levels of melatonin, while older adults have low levels, which may be linked to sleep problems in the elderly.
A study conducted in 2010 and published in the "Journal of Pineal Research" noted that circadian rhythms also influenced heart rate and blood pressure. Evidence pointed to the role of melatonin levels in the blood in maintaining heart, vascular and/or blood vessel functions including daily fluctuations in blood pressure and effects on the heart muscle. According to the study, melatonin also has antioxidant, anti-inflammatory and, possibly, even gene-regulating functions that influence cardiovascular health.
The circadian rhythm and the biological role of melatonin are linked to cardiovascular disease in complex ways that are still undergoing studies. However, it is known that heart attacks, angina or chest pain, cardiac arrest, irregular hearth rhythms and sudden death due to heart failure vary according to the time of day., The study concluded that changes in sleep patterns due to shift work and other reasons may increase the risk of cardiac arrest and other cardiovascular diseases.
The study published in the "Journal of Pineal Research" also noted that just as your body has a circadian rhythm that affects sleep and waking patterns, the cardiomyocytes or cells of the heart muscles also have circadian clocks that affect their function. The vascular smooth muscle cells also have these control rhythms. These circadian clocks in the individual heart and vascular cells are important because they can influence cardiovascular function by anticipating increased activity. For example, there is increased nervous stimulation to the heart which raises heart rate in the early morning hours as the circadian clocks prepare for you to wake up. This is thought to be linked to the reason why there are an increased number of heart attacks and strokes in the morning, than at any other time of the day or night.
Research published in the journal "The Annals of Medicine" in May 2010, suggested that melatonin may be able to treat several cardiovascular diseases. The study showed that when the hormone melatonin was given to rodents, it decreased hypertension or high blood pressure. Melatonin was also able to reduce abnormal heart function and heart tissue damage, helping to decrease the risk of cardiac arrest. Additionally, as melatonin does not have toxic side effects, it may be safer than some conventional drugs that are used to prevent heart failure. This study was conducted on rodents and the benefits and safety of using melatonin to treat cardiovascular disease in humans is not yet determined.