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How Do Sleep Duration & Quality Influence Cardiometabolic Outcomes?

Women sleeping happily
          Read time: 10 minutes

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 kept awake develop a peripheral syndrome characterized by increased metabolic rate and decreased body weight, leading to death after two to four weeks.2 Prolonged sleep deprivation is also fatal in humans, who die after developing a syndrome similar to those seen in rats. What remains unclear is whether death is due to the loss of sleep itself or to other factors involved, such as forced arousals and resulting stress on the body.2

Whether or not sleep loss itself is lethal, sleep deprivation in humans alters multiple aspects of behavior and physiology, including the cardiovascular system. 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 did get enough sleep (greater than seven hours in a 24-hour period);3 heart attack, coronary heart disease, stroke, and diabetes are among the adverse cardiometabolic risks of short sleep duration.3-5

Data from 487,200 adults 30-79 years of age found that individual and coexisting insomnia symptoms are independent risk factors for cardiovascular disease incidence, particularly among young adults or adults who have not developed hypertension.6 In this cohort, researchers tracked participants for nearly a decade. Participants who reported experiencing all three insomnia symptoms (problems falling asleep or staying asleep, waking too early, or struggling to focus during the day because of disrupted sleep) had an 18% increased chance of developing cardiovascular diseases compared with those who did not experience these symptoms.6

Those who reported trouble focusing during the day were 13% more likely to develop heart attack, stroke, and comparable diseases than people who did not have problems focusing.6 Those who found it difficult to fall asleep or stay asleep had a 9% higher chance of developing cardiovascular diseases, 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 cardiovascular disease risk later on in life.6

In a 2019 study, lower sleeping times and fragmented sleep (repetitive short interruptions of sleep) were independently associated with an increased risk of subclinical multiterritory atherosclerosis among 3,974 study participants.4 State-of-the-art imaging methods were used to quantify noncoronary atherosclerosis and coronary calcification in participants. Participants were divided into four groups: very short sleep duration (less than six hours), short sleep duration (six to seven hours), reference sleep duration (seven to eight hours), and long sleep duration (greater than eight hours). Consistent with prior studies, participants with very short sleep duration or short sleep duration had higher prevalence of classical cardiovascular risk factors.4

Acute sleep deprivation and sleep fragmentation may also be associated with impaired glucose metabolism,5 as it is well known that a close link exists between diabetes and cardiovascular disease.7 In a 2019 study, both diabetes mellitus and hypertension were more common in the group sleeping fewer than six hours per night, but 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, likely secondary to increased sympathetic nervous system activity and dysregulation of the hypothalamic-pituitary-adrenal axis. Researchers speculate that the disorder obstructive sleep apnea was a likely cause of sleep fragmentation in this sample.5

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 heart diseases.8,9 Not only do adults with OSA have an increased risk of developing comorbid cardiovascular disease, many may also experience worse outcomes.8

Interestingly, OSA is highly prevalent; it is estimated to affect 40-60% of US patients with cardiovascular disease. 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.8 A recent analysis of the global prevalence and burden of OSA estimated that 936 million (95% CI, 903-970 million) males and females 30 to 69 years of age have mild to severe OSA, and 425 million (95% CI, 399-450 million) have moderate to severe OSA globally. The prevalence was highest in China, followed by the United States, Brazil, and India.8,10 Furthermore, it has been estimated that 82% of men and 93% of women with moderate to severe OSA remain undiagnosed.11

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.9 But while multiple cardiovascular disease processes are associated with OSA, the relationship with hypertension has been most clearly established.8 Metabolic dysregulation is considered by some researchers as an underlying mechanism of OSA, which often leads to CVD.11 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 The 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.8,13 In the Sleep Heart Health Study, which analyzed data from 1,850 participants, researchers found that participants with a lower proportion of slow-wave sleep (the deepest stage of non-rapid eye movement sleep) had significantly greater odds of incident hypertension.8,14

Anxiety & Depression

When anxiety and depression start to negatively affect sleep patterns, this may also have a detrimental effect on heart health.15 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.15

A high level of anxiety and depression was detected in a 2019 cross-sectional study of 1,053 patients with a confirmed cardiac diagnosis; 54% met the criteria for severe depression and 19.2% for severe to very severe anxiety.16 Factors independently associated with both depressive and anxiety symptoms were post-traumatic stress disorder (PTSD) symptoms, a low level of self-esteem, high somatic symptoms, low physical and mental health component scores, active smoking, physical inactivity, and longer disease duration.16

In the current environment, shaped by the COVID-19 pandemic, many individuals have been exposed to unprecedented levels of anxiety and depression, as well as disturbed sleep, which can often lead to chronic insomnia.17 Pre-existing insomnia is a major risk factor for developing PTSD when exposed to a major stressor.17 A recent study showed that PTSD symptoms were reported by 7% of Wuhan residents after the COVID-19 outbreak, women in particular.18 Being younger than 35 years and following COVID-19 news updates for more than three hours a day was associated with elevated levels of anxiety compared with those who were older than 35 years and those who were less exposed to COVID-19 news updates.18

Steps to Improve Sleep

Diets high in vegetables, such as the Mediterranean-style diet and the vegetarian diet, have been shown to be associated with delayed progression of atherosclerotic plaques.19 In a 2018 observational study of older Australian women, a higher intake of vegetables (greater than three servings per day) and intake of cruciferous vegetables were inversely associated with common carotid artery IMT (CCA-IMT) and carotid plaque severity. Women consuming more than three servings of vegetables each day had ?4.6-5.0% lower mean CCA-IMT (P=0.014) and maximum CCA-IMT (P=0.004) compared with participants consuming less than two servings of vegetables.19

Different types of vegetables contain different levels of protective components. Cruciferous vegetables, such as cabbage, Brussels sprouts, cauliflower, and broccoli, as well as allium vegetables, such as onions, leek, and garlic, are rich sources of organosulfur compounds, which are proposed to be beneficial for cardiovascular health. Leafy green vegetables, such as spinach and lettuce, are a rich source of nitrate, which has been shown in clinical trials to lower blood pressure, a major risk factor for cardiovascular disease.19

A small 2016 study suggests that low fiber and high saturated fat and sugar intake is associated with lighter, less restorative sleep with more arousals.20 There is increasing evidence showing that sleep also has an influence on eating behaviors.21 Short sleep duration, poor sleep quality, and later bedtimes are all associated with increased food intake, poor diet quality, and excess body weight. Lack of sleep has been shown to increase snacking, the number of meals consumed per day, and the preference for energy-rich foods.21

Micronutrient intake has also been suggested to affect sleep patterns.22 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 sleep maintenance; and low intake of calcium and vitamin C with non-restorative sleep. Protein and carbohydrate deficiencies have also been associated with shorter sleep duration.22

In addition to diet, physical exercise, cognitive interventions, and relaxation techniques may help to induce sleep or help the body heal from insufficient sleep.17,23-25 Many study outcomes highlight the importance of healthy sleep habits for cardiovascular disease prevention.4-6 There is also evidence that sedentary behavior26 and ultra-processed food consumption27 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.17,26,27 While this type of screening has long been an important element of the functional medicine practitioner-patient relationship, it is particularly important now, as people of all ages worldwide learn to cope with the COVID-19 pandemic and its social implications.

Conclusion

Taken together, the studies outlined in this report illustrate the importance of healthy sleep habits for a healthy heart. While no one knows exactly when sleep deprivation turned into a competition (especially in the US) or a fear of “missing out” in modern society, the research underscores—again and again—the importance of sleep, not only for the heart 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 therapies to prevent or reverse cardiovascular damage. To learn more about the assessment, prevention, and management of cardiovascular disorders, please visit the following pages:

Learn More About Cardiometabolic Function

The cardio-focused physical exam 

Lifestyle interventions to modify cardiovascular disease risk 

Microbiome health and cardiometabolic conditions 

References

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  2. Cirelli C, Tononi G. Is sleep essential? PLoS Biol. 2008;6(8):e216. doi:1371/journal.pbio.0060216
  3. National Center for Chronic Disease Prevention and Health Promotion, Division of Population Health. Short sleep duration among US adults. CDC. Reviewed May 2, 2017. Accessed September 1, 2020. https://www.cdc.gov/sleep/data_statistics.html
  4. Domínguez F, Fuster V, Fernández-Alvira JM, et al. Association of sleep duration and quality with subclinical atherosclerosis. J Am Coll Cardiol. 2019;73(2):134-144. doi:1016/j.jacc.2018.10.060
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  12. Peppard PE, Young T, Palta M, Skatrud J. Prospective study of the association between sleep?disordered breathing and hypertension. N Engl J Med. 2000;342(19):1378-1384. doi:1056/nejm200005113421901
  13. Gonçalves SC, Martinez D, Gus M, et al. Obstructive sleep apnea and resistant hypertension: a case?control study. Chest.2007;132(6):1858-1862. doi:1378/chest.07-1170
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  16. Allabadi H, Alkaiyat A, Alkhayyat A, et al. Depression and anxiety symptoms in cardiac patients: a cross-sectional hospital-based study in a Palestinian population. BMC Public Health. 2019;19(1):232. doi:1186/s12889-019-6561-3
  17. 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. Published online April 4, 2020. doi:1111/jsr.13052
  18. Liu N, Zhang F, Wei C, et al. Prevalence and predictors of PTSS during COVID-19 outbreak in China hardest-hit areas: gender differences matter. Psychiatry Res. 2020;287:112921. doi:1016/j.psychres.2020.112921
  19. Blekkenhorst LC, Bondonno CP, Lewis JR, et al. Cruciferous and total vegetable intakes are inversely associated with subclinical atherosclerosis in older adult women. J Am Heart Assoc. 2018;7(8):e008391. doi:1161/jaha.117.008391
  20. 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:5664/jcsm.5384
  21. Chaput JP. Sleep patterns, diet quality and energy balance. Physiol Behav. 2014;134:86-91. doi:1016/j.physbeh.2013.09.006
  22. 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:3389/fneur.2017.00393
  23. 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:12659/msmbr.924085
  24. 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:1556/650.2020.31740
  25. 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. Published online January 25, 2020. doi:1080/17461391.2020.1716855
  26. 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:1016/j.sleep.2019.01.048
  27. 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.

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