Cardiovascular Disease and Sleep

Introduction

For the last century, our sleep duration has been steadily decreasing. Studies suggest that the average worker in a developed country is now only getting 6.5 hours of sleep per night.¹

Sleep has a large impact on many aspects of health, including mental wellbeing, stamina, and internal function. Specifically, new epidemiological studies have suggested that a lack of sleep can influence the development of cardiovascular disease, as well as other chronic conditions such as hypertension and diabetes.²

How much sleep do I need?

Adequate sleep duration can vary by age, health status, and activity level. However, the National Sleep Foundation recommends that an adult should receive between 7-9 hours of sleep per night. Ensuring that you are allowing your body to rest is vital for multiple internal functions like healing, mental fortification, and improving energy levels.

A study conducted among American nurses found that adults who sleep too little (fewer than 5 hours) and too much (more than 9 hours) were both at increased risk of coronary events.³ A coronary event, such as myocardial infarction (heart attack), is any adverse event impacted by the health of the coronary arteries. Clearly, the study shows that regulating your sleep between the recommended 7-9 hours can help your vascular network stay healthy and disease free.

However, people who experience a lack of sleep are also likely to have other risk factors increasing their risk of coronary events. These may include smoking, alcohol consumption, and being overweight. While sleep may not be the only answer to maintaining heart health, it must be prioritised alongside other risk factors in order to avoid cardiovascular disease. 

How Does Sleep Affect Your Heart Health?

Sleep conditions that can affect heart health

What is Sleep Apnea?

Sleep apnea is usually characterised by breathing difficulties while sleeping that prevent the sufferer from entering a deep sleep. The common signs of sleep apnea are breathing stopping and starting, gasping and choking, waking up often, and loud snoring.

These symptoms can result in chronic tiredness during the day, problems concentrating, mood swings, and persistent headaches. This can go on to affect the sufferer’s productivity and their ability to enjoy daily life in the face of exhaustion.

The most common form of sleep apnea is obstructive sleep apnea (OSA), which is suspected to affect 34% of adults assigned male at birth, and 17% of adults assigned female at birth.⁴ In this form, a blocked airway prevents air from filling the lungs, resulting in the periodic symptoms listed above. Although mild cases of OSA do not need treatment, some sufferers may benefit from the use of a CPAP machine, a device that keeps airways from becoming too narrow and allows the user to sleep more deeply.

Sleep Apnea and Heart Disease

The persistent pauses in sleep apnea often cause stress on the body, and can increase the risk of developing several chronic conditions including heart failure, stroke, and coronary heart disease. Heart disease is a leading cause of death in developed countries, and is commonly influenced by unhealthy risk factors like a bad diet, lack of physical activity, alcohol consumption, and smoking.

Sleep disorders, such as sleep apnea, can increase the risk of heart disease and heart arrhythmia. In fact, those with untreated sleep apnea are at a 140% increased risk for heart failure, and 30% increased risk of general coronary heart disease.⁵

Furthermore, while sleep apnea is an independent risk factor for heart disease, not only does being obese increase risk for having sleep apnea, but also for heart disease. It is estimated that between 60-90% of sleep apnea patients are also obese, meaning their chance of developing cardiovascular disease is doubled.⁶ Clearly, managing general health is the best way to prevent the development of heart disease, both via the treatment of sleep apnea if necessary, and weight, diet, and exercise monitoring. 

Sleep Disorders and Heart Health

Sleep and Blood Pressure

Your risk for hypertension (high blood pressure) is increased by a lack of sleep. Typically, blood pressure should decrease during sleep as a result of relaxation.

This low blood pressure period allows the veins to rest, and be restored from the stresses of the day. However, those who do not receive adequate sleep do not allow their cardiovascular system to rest, and therefore may have consistent high blood pressure.

A 2006 study showed that participants without hypertension severely increased their likelihood of developing the condition when they consistently received less than 5 hours of sleep per night.⁷ Furthermore, sleep conditions like insomnia and sleep apnea, which stress the body and raise blood pressure, have also been associated with the development of chronic hypertension.⁸

Sleep and Heart Attacks

Similar to the impact of sleep on blood pressure, a lack of sleep can also increase the risk for heart attack. A heart attack occurs when the blood vessels leading to the heart give out, and blood flow is cut off partially or completely. Heart attacks may occur after chronic untreated cardiovascular disease, hypertension, and other conditions that affect circulatory flow.

Therefore, where lack of sleep is a risk factor for those conditions, it also becomes a risk factor for heart failure. As mentioned earlier, those with sleep apnea are at 140% increased risk of heart failure, and the same is true for those with insomnia, lack of sleep, or other conditions. 

Sleep and Stroke

Strokes occur when blood flow to the brain is temporarily cut off, seriously impacting a sufferer's motor function and other mental capabilities. Strokes can be minor or major, and are the leading cause of long-term disability in developed countries.

Like heart attacks, strokes are often the result of untreated chronic health problems like diabetes, obesity, cardiovascular disease, and hypertension. As we have seen, all of the risk factors for stroke are impacted by lack of sleep, and therefore lack of sleep indirectly increases risk for stroke events.

One study showed that those with obstructive sleep apnea (OSA) were at a three-fold increased risk of ischaemic (minor) stroke. Furthermore, those who suffer a stroke may go on to develop a sleeping disorder afterwards as a result of medications, discomfort, and other comorbidities - seriously impacting their ability to recover.⁹

Sleep and Obesity

As mentioned earlier, obesity is a leading cause of sleep apnea, both of which increase the risk for heart disease. It is theorised that fat deposits in the neck lead to airway narrowing, causing  breathing difficulties that comprise sleep apnea. Besides sleep apnea, obesity may also impact a sufferer’s ability to be comfortable during sleep, lowering sleep duration and quality.

While obesity may lead to a lack of sleep, lack of sleep may also lead to obesity. New studies have shown that receiving less than 5 hours of sleep per night can impact the body’s metabolism, insulin levels, and other processes that can result in weight gain.¹⁰ 

Sleep and Heart Rate

During sleep, heart rate and blood pressure are reduced as the body enters unconsciousness and breathing becomes regulated. This relaxed period is extremely important for the interconnected systems of the body to receive a break and recuperate from daily stress. When this period is interrupted by sleep apnea, or lack of sleep, the body does not receive the rest it requires and chronic fatigue can ensue.

This sense of tiredness often leads to a mental decline, and can result in the development of other issues like depression and anxiety. Anxiety may induce a persistent raised heart rate, and keep the body in a state of stress. 

Sleep and Chest Pain

Chest pain (angina) occurs as a result of poor blood flow through the circulatory system. This symptom may occur after a surge in heart rate, persistent high blood pressure, or other coronary events. These risk factors are associated with a lack of sleep, and may lead a sufferer to experience angina.

Non-cardiac chest pain, such as heartburn or acid reflux, can also cause discomfort while sleeping, and result in decreased sleep quality. 

Insomnia

Insomnia is the presence of regular sleep problems. Its symptoms include difficulty falling asleep, waking up in the night, waking up too early and being unable to go back to sleep, and finding napping difficult besides tiredness. The common causes of insomnia are stress/anxiety, uncomfortable sleeping conditions, alcohol, caffeine, nicotine, jet lag, and shift work.

Treating insomnia can be tricky since its causes are multivariate; however, you may try setting a consistent sleep schedule, doing something relaxing an hour before bed, and making sure your sleeping situation is comfortable.

Sleep and Heart Failure

Similar to a heart attack, heart failure occurs when the muscles of the heart stop pumping blood to the rest of the body. It is caused by many of the same risk factors as heart attacks such as high blood pressure, diabetes, and cardiovascular disease.

As we have seen, all of these conditions are impacted by a lack of sleep and sleep apnea. Therefore, the risk of heart failure is significantly increased when sleep duration and quality are not adequate. 

Sleep Tips for People With Heart Problems

The process of improving sleep is often referred to as sleep hygiene. Improving sleep hygiene can be relatively simple.

Here are a few tips.

  • Ensure your sleeping conditions are comfortable, quiet, and dark.
  • Develop a pre-bed routine that includes relaxing activities. Reading a book, taking a bath, or having non-caffeinated tea are good examples.
  • Put electronic devices away, as the blue light from screens can alter the circadian rhythm.
  • Try keeping a sleep diary in order to track your daily habits that may be contributing to a lack of sleep.
  • Look at the resources on Sleep Foundation for more information on improving sleep hygiene.

When To See a Doctor

You should see a doctor if you are having consistent and impactful sleep difficulties. This includes chronic fatigue, irritability, and headaches. Furthermore, you should contact a doctor if you are experiencing the symptoms of heart disease like chest pain, shortness of breath, general pain, weakness, and numbness.

FAQs

Sleeping Too Much and Heart Health

Sleeping too much has also been associated with heart disease, where those who receive more than 9 hours a night can impact the likelihood of coronary events. It is suspected that sleep duration forms a bell-shaped curve with heart disease, where at both ends (too much sleep and too little sleep) heart health is negatively impacted. The Sleep Foundation recommends that an average adult sleep between 7-9 hours per night. 

Sleeping Too Little and Heart Health

As mentioned above, sleeping too little has a negative impact on heart health. It has been associated with an increased risk of high blood pressure, cardiovascular disease, heart attack, and stroke. 

Does Sleeping Position Affect Heart Health?

Sleeping position can impact heart health in the sense that it may impact sleep quality. Sleeping comfortably is an important factor for sleep quality, but varies from person to person.

Some sufferers of sleep apnea find that side sleeping reduces symptoms, and that back sleeping may exacerbate them. Furthermore, some studies show that right side sleeping may be better for sufferers of heart failure, but the scientific evidence is limited. 

References: 

  1. Nagai M, Hoshide S, Kario K. Sleep duration as a risk factor for cardiovascular disease- a review of the recent literature. Curr Cardiol Rev. 2010;6(1):54-61. 
  2. Hirshkowitz, M., Whiton, K., Albert, S. M., Alessi, C., Bruni, O., DonCarlos, L., Hazen, N., Herman, J., Katz, E. S., Kheirandish-Gozal, L., Neubauer, D. N., O'Donnell, A. E., Ohayon, M., Peever, J., Rawding, R., Sachdeva, R. C., Setters, B., Vitiello, M. V., Ware, J. C., & Adams Hillard, P. J. (2015). National Sleep Foundation's sleep time duration recommendations: methodology and results summary. Sleep health, 1(1), 40–43.
  3. Ayas, N. T., White, D. P., Manson, J. E., Stampfer, M. J., Speizer, F. E., Malhotra, A., & Hu, F. B. (2003). A prospective study of sleep duration and coronary heart disease in women. Archives of internal medicine, 163(2), 205–209. 
  4. Javaheri, S., Barbe, F., Campos-Rodriguez, F., Dempsey, J. A., Khayat, R., Javaheri, S., Malhotra, A., Martinez-Garcia, M. A., Mehra, R., Pack, A. I., Polotsky, V. Y., Redline, S., & Somers, V. K. (2017). Sleep Apnea: Types, Mechanisms, and Clinical Cardiovascular Consequences. Journal of the American College of Cardiology, 69(7), 841–858 
  5. Jean-Louis G, Zizi F, Brown D, Ogedegbe G, Borer J, McFarlane S. Obstructive sleep apnea and cardiovascular disease: evidence and underlying mechanisms. Minerva Pneumol. 2009;48(4):277-293.
  6. Pillar, G., & Shehadeh, N. (2008). Abdominal fat and sleep apnea: the chicken or the egg?. Diabetes care, 31 Suppl 2(7), S303–S309.
  7. Nagai M, Hoshide S, Kario K. Sleep duration as a risk factor for cardiovascular disease- a review of the recent literature. Curr Cardiol Rev. 2010;6(1):54-61.
  8. Calhoun DA, Harding SM. Sleep and hypertension. Chest. 2010;138(2):434-443.
  9. Benjamin EJ, Blaha MJ, Chiuve SE, Cushman M, Das SR, Deo R, et al.; American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Heart disease and stroke statistics-2017 update: a report from the American Heart Association. ‘Circulation’. 2017; 135:e146–e603
  10. Beccuti G, Pannain S. Sleep and obesity. Curr Opin Clin Nutr Metab Care. 2011;14(4):402-412.

Kristen Bowles

Masters of Science - MSc Epidemiology Student, London School of Hygiene and Tropical Medicine, England
Kristen graduated as Summa Cum Laude and is now pursuing Masters of Epidemiology in LSHTM.
Experienced in cultural anthropology from the University of St. Andrews, and hopes to continue working in Europe with a special focus on medical mistrust and how these social factors influence health data, equity, and disease spread.

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