insights

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In 2017, sleep scientist Matthew Walker, author of the book Why We Sleep, made the assertion that humans are the only species who deliberately deprive themselves of sleep for no apparent [biological] gain.¹ Although many people consider short sleepers “productive” members of society, the harmful consequences of sleep deprivation have been detailed in clinical studies.²

In the most dramatic cases, prolonged sleep deprivation may lead to death. For example, rats that are kept awake accumulate reactive oxygen species and consequent oxidative stress, specifically in the gut, potentially contributing to premature death.³ In addition, they may develop a peripheral syndrome characterized by increased metabolic rate and decreased body weight, leading to death after two to four weeks.² Sleep deprivation in humans alters multiple aspects of both behavior and physiology, and observational studies have associated chronic sleep deprivation with increased risk of cardiovascular events and all-cause mortality.⁴

Sleep & Cardiometabolic Risks

In the US, adults who are short sleepers (less than seven hours per 24-hour period) are more likely to report a variety of chronic health conditions compared to those who get enough sleep (greater than seven hours in a 24-hour period);⁵ heart attack, coronary heart disease, stroke, and diabetes are among the adverse cardiometabolic risks of short sleep duration.^5–7 Data from 487,200 adults 30-79 years of age found that individual and coexisting insomnia symptoms are independent risk factors for cardiovascular disease (CVD) incidence, particularly among young adults or adults who have not developed hypertension.⁸ In this cohort, researchers tracked participants for nearly a decade, and those who reported trouble focusing during the day were 13% more likely to develop heart attack, stroke, and comparable diseases than those who did not have problems focusing.⁸ Participants who found it difficult to fall asleep or stay asleep had a 9% higher chance of developing CVDs, while those who woke up too early were 7% more likely to experience a stroke, heart attack, or similar incident. The results suggest that identifying insomnia, particularly in young people, may reduce CVD risk later on in life.⁸

Acute sleep deprivation and sleep fragmentation may also be associated with impaired glucose metabolism.⁷ In a 2019 study, both diabetes mellitus and hypertension were more common in the group sleeping fewer than six hours per night.⁷ Researchers noted that neither blood pressure nor glucose metabolism was assessed with sufficiently comprehensive measures to explore these factors as potential effect mediators; however, insomnia itself is associated with increased risk of vascular disease. Researchers speculated that obstructive sleep apnea was a likely cause of sleep fragmentation in this sample.⁷

Obstructive Sleep Apnea

Cardiovascular disease remains a highly prevalent cause of morbidity and mortality worldwide, and accumulating evidence suggests that sleep disorders like obstructive sleep apnea (OSA) may be associated with the development of a range of cardiovascular diseases.^9,10 Not only do adults with OSA have an increased risk of developing comorbid CVD, many may also experience worse outcomes.⁹

Interestingly, OSA is highly prevalent, especially among those with cardiovascular dysfunction; it is estimated to affect 40-60% of US patients with CVD.⁹ This prevalence is also increasing, with these figures representing a 30% increase over the previous two decades. Researchers speculate that this may be related to the obesity epidemic as well as an aging population.⁹ A 2018 meta-analysis found that OSA was associated with a significantly increased risk of major adverse cardiovascular events, including all-cause or cardiovascular death, myocardial infarction, stroke, repeat revascularization, and heart failure.¹⁰ Metabolic dysregulation is considered by some researchers as an underlying mechanism of OSA, which often leads to CVD.¹¹

While multiple CVD processes are associated with OSA, the relationship with hypertension has been most clearly established.⁹ Typically, patients with OSA have greater levels of endothelin and lower levels of nitric oxide than healthy sleepers, which may explain why they often experience greater blood vessel constriction.¹¹ A study by Peppard et al, which followed 709 patients in the Wisconsin Sleep Cohort, found a relationship between the severity of OSA and the relative risk of developing hypertension during follow-up.¹² This relationship is particularly strong between OSA and resistant hypertension; for example, one study found the prevalence of OSA to be 71% in patients with resistant hypertension versus 38% in those with essential hypertension.^9,13

Steps to Improve Sleep

Many study outcomes highlight the importance of healthy sleep habits for CVD prevention,^6–8 and a nutritious diet, physical exercise, cognitive interventions, and relaxation techniques may all help to induce sleep or help the body heal from insufficient sleep.^14–17 Specific to nutrition, deficiencies in vitamin B1, folate, phosphorus, magnesium, iron, zinc, and selenium have been associated with shorter sleep duration; lack of alpha-carotene, selenium, and calcium with difficulty falling asleep; low intake of vitamin D and lycopene with problems with sleep maintenance; and low intake of calcium and vitamin C with non-restorative sleep.¹⁸ Protein and carbohydrate deficiencies have also been associated with shorter sleep duration,¹⁸ and a small 2016 study suggests that low fiber and high saturated fat and sugar intake are associated with lighter, less restorative sleep.¹⁹

Increasing evidence also demonstrates a reverse relationship, with disrupted sleep patterns prompting unhealthy eating behaviors²⁰ that may contribute to cardiometabolic risk. Short sleep duration, poor sleep quality, and later bedtimes are all associated with increased food intake, poor diet quality, and excess body weight. In addition, lack of sleep has been shown to increase snacking, the number of meals consumed per day, and the preference for energy-rich foods.²⁰

Research results suggest that sedentary behavior²¹ and ultra-processed food consumption²² may be associated with anxiety-induced sleep disturbance. Studies point to the need for mental health screening for all, as well as the integration of lifestyle interventions to modulate sleep.^14,21,22 When anxiety and depression start to negatively affect sleep patterns, this may have a detrimental effect on heart health. Evidence suggests that persistent anxiety and depression could be tied to negative long-term effects on cardiovascular health and may play a major role in triggering critical cardiac events like myocardial infarction.²³

Conclusion

Taken together, the studies outlined in this report illustrate the importance of healthy sleep habits for not only heart health but for the entire body as a form of healing. A close working relationship between clinician and patient can help identify sleep troubles early on so that they may be targeted with behavioral and lifestyle therapies to prevent or reverse cardiovascular damage. Learn more about tools and strategies to help patients achieve sustainable lifestyle change and improve their well-being through IFM’s new course Lifestyle: The Foundations of Functional Medicine.

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Spiritual needs, stress, and cardiovascular responses

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References

1. Walker M. Why We Sleep: Unlocking the Power of Sleep and Dreams. Scribner; 2017.
2. Cirelli C, Tononi G. Is sleep essential? PLoS Biol. 2008;6(8):E216. doi:10.1371/journal.pbio.0060216.
3. Vaccaro A, Kaplan Dor Y, Nambara K, et al. Sleep loss can cause death through accumulation of reactive oxygen species in the gut. Cell. 2020;181(6):1307-1328. doi:10.1016/j.cell.2020.04.049.
4. Wang Y-H, Wang J, Chen S-H, et al. Association of longitudinal patterns of habitual sleep duration with risk of cardiovascular events and all-cause mortality. JAMA Netw Open. 2020;3(5):E205246. doi:10.1001/jamanetworkopen.2020.5246.
5. National Center for Chronic Disease Prevention and Health Promotion Division of Population Health. Short sleep duration among US adults. CDC. https://www.cdc.gov/sleep/data_statistics.html . Published May 2, 2017. Accessed October 26, 2021.
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9. Tietjens JR, Claman D, Kezirian EJ, et al. Obstructive sleep apnea in cardiovascular disease: a review of the literature and proposed multidisciplinary clinical management strategy. J Am Heart Assoc. 2019;8(1):e010440. doi:10.1161/JAHA.118.010440.
10.  Benjafield AV, Ayas NT, Eastwood PR, et al. Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis. Lancet Respir Med. 2019;7(8):687-698. doi:10.1016/S2213-2600(19)30198-5.
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14.  Altena E, Baglioni C, Espie CA, et al. Dealing with sleep problems during home confinement due to the COVID-19 outbreak: practical recommendations from a task force of the European CBT-I Academy. J Sleep Res. 2020;29(4):e13052. doi:10.1111/jsr.13052.
15.  Wu K, Wei X. Analysis of psychological and sleep status and exercise rehabilitation of front-line clinical staff in the fight against COVID-19 in China. Med Sci Monit Basic Res. 2020;26:E924085. doi:10.12659/MSMBR.924085.
16.  Tamás RB, Perczel-Forintos D, Máté O, Gyenge Z. Treatment of somatic symptom disorder in childhood: evidence-based psychotherapy interventions. Orv Hetil. 2020;161(25):1050-1058. doi:10.1556/650.2020.31740.
17.  Crowley SK, Rebellon J, Huber C, Leonard AJ, Henderson D, Magal M. Cardiorespiratory fitness, sleep, and physiological responses to stress in women. Eur J Sport Sci. 2020;20(10):1368-1377. doi:10.1080/17461391.2020.1716855.
18.  Frank S, Gonzalez K, Lee-Ang L, Young MC, Tamez M, Mattei J. Diet and sleep physiology: public health and clinical implications. Front Neurol. 2017;8:393. doi:10.3389/fneur.2017.00393.
19.  St Onge MP, Roberts A, Shechter A, Choudhury AR. Fiber and saturated fat are associated with sleep arousals and slow wave sleep. J Clin Sleep Med. 2016;12(1):19-24. doi:10.5664/jcsm.5384.
20.  Chaput JP. Sleep patterns, diet quality and energy balance. Physiol Behav. 2014;134:86-91. doi:10.1016/j.physbeh.2013.09.006.
21.  Vancampfort D, Van Damme T, Stubbs B, et al. Sedentary behavior and anxiety-induced sleep disturbance among 181,093 adolescents from 67 countries: a global perspective. Sleep Med. 2019;58:19-26. doi:10.1016/j.sleep.2019.01.048.
22.  Werneck AO, Vancampfort D, Oyeyemi AL, Stubbs B, Silva DR. Joint association of ultra-processed food and sedentary behavior with anxiety-induced sleep disturbance among Brazilian adolescents. J Affect Disord. 2020;266:135-142. doi:10.1016/j.jad.2020.01.104.
23.  Kapfhammer HP. The relationship between depression, anxiety and heart disease – a psychosomatic challenge. Psychiatr Danub. 2011;23(4):412-424.