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Sleep, Cardiovascular Health, and Melatonin

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Earlier this year, the American Heart Association’s (AHA) checklist containing the key determinants of cardiovascular health was updated to contain a new pillar: sleep. 1 Updated from Life’s Simple 7, released in 2010, the new and improved Life’s Essential 8 (https://www.heart.org/en/healthy-living/healthy-lifestyle/lifes-essential-8) includes the seven previous metrics (smoking status, diet, physical activity, body weight, blood pressure, cholesterol, and blood glucose) with the addition of sleep quantity as the eighth factor. These metrics can be used as both predictors of, and guidelines for improving, cardiovascular health. 2

Cardiovascular Sleep

As the leading cause of death worldwide, 3 cardiovascular diseases remain an area of health in which accurate assessment and swift, effective management is critical. In addition to outcomes such as strokes and myocardial infarction, which have both high morbidity and mortality, suboptimal cardiovascular health can also increase the risk of noncardiovascular conditions such as cognitive decline, renal disease, and cancer, among others. 4

In many cases, cardiovascular diseases are largely preventable and highly treatable. 5 The role of naturopathic medicine in preventing and improving various parameters of cardiovascular health is well-studied. Naturopathic interventions—including supplementation with various vitamins, minerals, and flavonoids—including niacin; botanicals such as garlic and hawthorn; 6 stress-reduction techniques; 8 low-sodium diet; 9 and regular aerobic exercise  10 are evidence-based therapies for managing and improving cardiovascular disease outcomes. Sleep, as an additional facet of cardiovascular health, can encompass numerous additional naturopathic interventions. The effects of melatonin on sleep and cardiovascular health are described below.

Sleep and Cardiovascular Health

Sleep as an important determinant of health is not a novel concept. The role of sleep in the regulation of virtually every body’s system and processes—such as immune regulation, growth, tissue repair, cognitive function, and metabolic regulation, among others—is well-documented. 11 Many of the detrimental impacts of sleep deprivation on the body are due to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and impaired cortisol secretion 12,13 producing inflammation and increased sympathetic nervous system activity, 14 that causes the body to behave as if in fight-or-flight mode.

Issues pertaining to sleep and insomnia are a common complaint in family practice, with up to one-third of the population experiencing chronic insomnia. Insomnia is an underrecognized and undertreated issue. It is often a comorbidity with other conditions, some of which are cardiovascular, such as hypertension and ischemic heart disease. 15 Middle-aged individuals without a history of sleep disorders with a self-reported total sleep time of fewer than 5 hours per night were found to have a significantly increased risk of developing hypertension over an 8–10 year period (hazard ratio 2.10), compared to those sleeping 7–8 hours per night, even after controlling for confounding factors including diabetes and obesity. 16 Moreover, individuals with fewer than 6 hours of sleep per night over a 9 year period also exhibited a significantly increased all-cause mortality rate, including death from heart disease and stroke, in comparison to those sleeping 7–8 hours per night. 17 The detrimental impact of chronic sleep deprivation on cardiovascular health is undeniable. But insufficient sleep can impact cardiovascular parameters in the much shorter term: Following just one night of sleep deprivation, blood pressure was found to be significantly elevated among both hypertensive and normotensive adults. 19,20

Due to the high prevalence and severe health impacts of sleep dysfunction among patients complaining of sleep-related issues, cardiovascular sequelae must be prevented. In those with existing cardiovascular conditions, sleep should be considered as a potential contributing factor.

Cardiovascular Sleep

Sleep and Cardiovascular Benefits of Melatonin

Melatonin is most commonly known as a sleep-aid supplement. This endogenously produced hormone is regulated by light exposure, maintaining the circadian rhythm and facilitating the onset of sleep. 21 A meta-analysis reviewing 17 studies which examined the use of melatonin for sleep concluded melatonin supplementation significantly reduced sleep-onset latency, increased sleep efficiency, and increased total sleep time. 22

In addition to its use as a sleep aid, melatonin has many other health-promoting properties, including immunomodulation and antioxidant activity. Melatonin levels have been found to be inversely proportional to cardiovascular health, with lower levels found among those with cardiovascular disease. 23 Supplementation with melatonin also has a positive impact on cardiovascular health. A randomized, double-blind, placebo-controlled, crossover trial showed that supplementation with 2.5 mg of melatonin orally one hour before bed for a three-week duration significantly reduced nighttime systolic and diastolic blood pressure (by 6 mmHg and 4 mmHg, 24respectively) in adult men with untreated hypertension. 25 These reductions are considered clinically significant, 26 and more predictive of cardiovascular health than daytime blood-pressure readings. 27 Heart rate was unaffected by supplementation, and a single dose of melatonin was not found to have an effect on blood pressure. 28

The blood pressure–lowering effects of 5 mg of melatonin have also been confirmed in patient populations without cardiovascular disease. A meta-analysis found a significant systolic and diastolic blood–pressure reduction of 3.43 mmHg and 4.57 mmHg, respectively, with melatonin doses ranging from 3 to 10 mg per day for the duration of 6–12 weeks compared to control. 29 Furthermore, supplementation has also been found to exert positive effects on additional parameters of cardiovascular health: Adults with metabolic syndrome supplementing with 5 mg of melatonin per day for 2 months had a significant reduction in LDL cholesterol and markers of oxidative stress, in addition to systolic and diastolic blood-pressure reductions. 30

Although supplementation may be the best way to achieve therapeutic doses, consumption of melatonin-rich foods may also modulate endogenous melatonin production. Melatonin can be found in both plant and animal food sources but is present in the greatest quantities in plants. 31 Consuming foods containing trace amounts of melatonin, including walnuts and grapes, has been found to increase endogenous melatonin levels. Regular consumption of these foods has also been associated with a reduced risk of cardiovascular diseases. 32 The relationship between consumption of these foods, melatonin levels, and cardiovascular disease risk is not yet clear; however, as with most plants, the synergistic effects of numerous phytochemicals and nutrients all contribute to the food’s health benefits. Nonetheless, consistent research indicating that regular consumption of these foods lowers cardiovascular disease risk makes these foods a great option for those looking to preserve cardiovascular health.

Take-Away Messages

Overall, sleep is a crucial component of wellbeing, including cardiovascular health. The updated AHA guidelines reflect the importance of considering sleep quantity when assessing cardiovascular health and provide general parameters to aim for to optimize cardiovascular health. Naturopathic interventions to improve sleep, such as melatonin, can be additional treatments to consider when supporting patients with cardiovascular diseases. The holistic nature of these guidelines emphasizes the interconnectedness of all aspects of health and the importance of assessing and treating the whole person, one of the key principles of naturopathic medicine.

References
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