Sleep and Heart Health

By Gena Krikler,

Sleep is important for overall health, and for the normal functioning of many systems. Although there is no clear understanding of why sleep has evolved in animals, it is evident that it is very important for humans to sleep between 6-10 hours per night to maintain their health. The adverse effects of poor sleep have been extensively studied. Heart health is no exception; many studies have described the effects of sleep patterns on both healthy hearts and different heart diseases.

It is been found that short duration of sleep and poor subjective sleep quality elevate the risk for insulin resistance, the metabolic syndrome, obesity, type 2 diabetes and incident cardiovascular disease¹. Humans (as well as many other living organisms) have an innate circadian rhythm, also known as a ‘biological clock’, that is a natural twenty-four hour cycle of physical, mental and biological changes. This circadian rhythm causes humans to sleep at certain times and be awake at others. Disruption of the circadian rhythm has been linked to an increased incidence of cardiometabolic disease, and misalignment of sleep timing (sleeping not in accordance with your circadian rhythm) is associated with metabolic risk factors that predispose patients to diabetes and artherosclerotic cardiovascular disease².

Sleep disorders that cause sleep disturbance, including sleep apnea and insomnia, confer risk for cardiometabolic disease³. Obstructive sleep apnea is a common sleep-related breathing disorder that is characterized by repetitive episodes of apnea (stopping breathing) or reduced inspiratory airflow due to upper airway obstruction during sleep. These obstructions can depress myocardial contractility, activate the sympathetic nervous system (‘fight or flight response’), raise blood pressure, raise heart rate, increase myocardial wall stress, depress parasympathetic activity (‘rest and digest response’), provoke oxidative stress and systemic inflammation, activate platelets and impair vascular endothelial function⁴. There is an association between obstructive sleep apnea and hypertension, coronary heart disease, cardiac arrhythmia and heart failure, likely due to a combination of these factors⁴. It appears that the successful treatment of obstructive sleep apnea with continuous positive airway pressure can improve cardiovascular outcomes⁵.

Obstructive sleep apnea and Cheyne-Stokes breathing (another form of sleep apnea) are common among patients with heart failure; these sleep disorders are together referred to as sleep disordered breathing. It is unclear if sleep disordered breathing is a result of heart failure because many cases are undiagnosed before heart failure. It has been found that among patients with heart failure, as high as 50% may have sleep disordered breathing⁶. Furthermore, heart failure accompanied by sleep disordered breathing is associated with an increased risk of death when compared to heart failure in the absence of sleep disordered breathing⁷.

Overall, normal sleep patterns and heart health are closely related in both healthy hearts and patients with varying heart diseases. Following your body’s natural sleep patterns and maintaining normal, undisturbed sleep patterns will help keep your heart healthy!

References

1.       Buxton, O. M. & Marcelli, E. Short and long sleep are positively associated with obesity, diabetes, hypertension, and cardiovascular disease among adults in the United States. Soc. Sci. Med. 71, 1027–1036 (2010).

2.       Wong, P. M., Hasler, B. P., Kamarck, T. W., Muldoon, M. F. & Manuck, S. B. Social Jetlag, Chronotype, and Cardiometabolic Risk. J. Clin. Endocrinol. Metab. jc.2015–2923 (2015). doi:10.1210/jc.2015-2923

3.       Grander, M. A., Jackson, N. J., Pak, V. M. & Gehrman, P. R. Sleep disturbance is associated with cardiovascular and metabolic disorders. J. Sleep Res. 21, 427–433 (2012).

4.       Bradley, T. D. & Floras, J. S. Obstructive sleep apnoea and its cardiovascular consequences. Lancet 373, 82–93 (2009).

5.       Narkiewicz, K. et al. Nocturnal continuous positive airway pressure decreases daytime sympathetic traffic in obstructive sleep apnea. Circulation 100, 2332–2335 (1999).

6.       Javaheri, S. et al. Occult sleep-disordered breathing in stable congestive heart failure. Ann Intern Med 122, 487–492 (1995).

7.       Wang, H. et al. Influence of Obstructive Sleep Apnea on Mortality in Patients With Heart Failure. J. Am. Coll. Cardiol. 49, 1625–1631 (2007).