Sunlight and Cardiac Rhythms
How the Sun Affects Your Heart?
Undoubtedly, the sun is the source of life on Earth. It has countless health benefits as well. To your amazement, this article is designed to tell you the significant impact of sunlight on our heart’s health.
The sun is known to influence our circadian rhythms. These are the natural cycles that follow a 24-hour pattern. For example, sleep and wakefulness cycle. This cycle is controlled by a master clock located in the brain called the suprachiasmatic nucleus (SCN). It gets signals from the eyes about the dark and light cycles of the environment.
The SCN sends signals to various body organs including the heart. This helps to synchronize the organs’ functions with the day and night cycle.
Heart
Interestingly, the heart is among one of the organs that has its own circadian rhythm. It means that its activity and functions fluctuate throughout the day and night. The blood pressure, heart rate, vascular tone, and cardiac output, all are impacted by the circadian rhythm. They are higher during the daytime and lower at night.
Moreover, the circadian rhythm also influences the heart’s electrical activity. We know that the heart’s electrical activity is crucial for the contraction and relaxation of the cardiac muscles. ECG (electrocardiogram) measures the heart’s electrical activity. It records the waves of depolarization and depolarization of the cardiac cells.
Electrocardiogram
The ECG represents various patterns of waves, called P, QRS, and T. These correspond to the different phases of the cardiac cycle. The ECG also shows the intervals between the waves, such as the PR interval, the QRS interval, and the QT interval, which reflect the duration of the electrical events in the heart.
We know the ECG parameters are not always the same. They change according to the circadian rhythm. Like, the heart rate and QRS interval are greater during the day and lower during the night. Whereas, the QT interval is low during the day and high during the night.
These changes are physiological and adaptive. Indeed, they help the heart to cope with the numerous demands of day and night. However, these fluctuations can become pathological and dangerous if they are disturbed by external factors, like sunlight.
Role of Sunlight
Sunlight is the main factor that regulates the circadian rhythm of the 24-hour cycle. It does so by suppressing the melatonin secretion. Melatonin is a hormone that is produced by the pineal gland during the night and signals the onset of darkness.
Functions of Melatonin
Melatonin is known for its numerous effects on the body. The following are some major impacts on the heart’s functions:
It modulates the circadian rhythm of the cardiac function.
It can lower blood pressure, heart rate, vascular tone, and cardiac output.
It can affect the heart’s electrical activity by prolonging the QT interval and boosting the heart rate variability.
Undoubtedly, these effects are significant and protective. They reduce the cardiac workload and the chances of arrhythmias, the irregular heartbeats that can lead to the following complications:
Sudden cardiac death
Stroke
Heart failure
Adverse Effects of Excessive Sunlight
Excessive sunlight exposure can interfere with the normal circadian rhythm of the heart. It adversely affects cardiac functions. If the sunlight exposure is too early in the morning or too late in the evening, it can do the following:
Shift the circadian rhythm’s phase.
Disrupt the resonation between the internal clock and the external environment.
Cause a mismatch between the cardiac function and the daily activities.
Increase the chances of diseases like myocardial infarction, angina, or ischemia.
Intense or Prolonged Sunlight Exposure
Intense or prolonged sunlight exposure causes the following:
Oxidative stress
Inflammation
Damage to the cardiac cells and tissues
Impair the heart’s electrical and mechanical properties
Escalate the probability of arrhythmias, predominantly ventricular arrhythmias, the most dangerous ones.
Therefore, sunlight can affect our hearts both positively and negatively. It depends on the timing, duration, and intensity of the exposure. It is necessary to balance the sunlight exposure and follow the recommendations provided below:
• Avoid sunlight exposure during the day’s peak hours, which are between 10 a.m. and 4 p.m. It is the time when the UV rays are the most harmful and intense.
• Wear appropriate clothes, sunglasses, and apply sunscreen to protect the eyes and skin from harmful radiation.
• Expose to sunlight in the morning, recommended between 6 a.m. and 8 a.m. During this time the sunlight is most effective for the circadian rhythm and boosting the mood.
• Avoid exposure to sunlight in the evening.
• Get enough sleep, approximately between 7 and 9 hours per night. Maintain a regular sleep schedule. This helps the body and heart to recover and regenerate.
Conclusion
Indeed, sunlight and cardiac rhythms are linked to each other. They impact each other in numerous aspects. By following the recommended tips given in the article, you can not only enjoy the sunlight benefits but also prevent the risks.
Sources
· The effects of sunlight on the heart
· Circadian Rhythms and the Heart
· Melatonin and the cardiovascular system
· Sunlight and the heart: Potential role of vitamin D in the modulation of cardiac function
· The effect of sunlight exposure on the QT interval of the electrocardiogram in healthy volunteers
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