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The primary effects of insomnia typically are poor attention and concentration, memory difficulties, low mood, irritability, fatigue, and worry about sleep. There typically is little short term risk to physical health from insomnia and people can continue to function, although not optimally, on limited sleep (see Jacobs, 1998).
Over time, however, there has been increasing evidence of the detrimental effects of getting too little sleep (see Epstein & Mardon, 2007). Getting too little sleep has been associated with an increased risk of obesity, diabetes, and heart disease. Problems such as headaches, stomach upset, and aches and pains can develop after even a few days of poor sleep.
Over time, sleep loss adds up with increasingly poor cognitive functioning. Drowsy driving is a terrifying possibility when drivers suddenly experience micro-sleeps or falling asleep at the wheel. A vast amount of productivity is lost to the economy. And what about the high cost of a person’s sleep medications and supplements taken to deal with insomnia? In short, there are many costs of getting poor sleep. But does poor sleep directly affect heart health?
For some time, an association between certain sleep disorders (sleep-disordered breathing) and various cardiac problems, including heart arrhythmias, has been known (Somers & Javaheri, 2017). Specifically, obstructive sleep apnea has well-known and strong effects on the heart and its function. This is because periodic breathing pauses, characteristic of sleep apnea, have numerous negative impacts on the heart including low oxygen levels, high carbon dioxide levels, increased acidity of the blood, sympathetic nervous system activation, and rapid fluctuations in heart wall stress.
It is completely reasonable that stresses such as these, over time, could result in electrical timing problems in the heart. Sleep apnea has been found to increase the risk of new-onset atrial fibrillation as well as increase recurrence of atrial fibrillation after cardioversion, if sleep apnea was not well managed by positive airway pressure therapy (CPAP). Short sleep has been associated with a number of problems including high blood pressure, obesity, and impaired glucose tolerance (Genuardi et al., 2019).
Atrial fibrillation is a significant medical problem as it can cause unpleasant sensations such as palpitations, weakness, fatigue, dizziness, shortness of breath, and chest pain. Others have atrial fibrillation without any of these symptoms and are unaware that they have it. While usually not life-threatening, atrial fibrillation increases the risk of stroke and heart failure. It may require emergency treatment.
Thus, the effects of sleep-disordered breathing on the heart, especially in more severe cases of apnea, make a great deal of sense considering the severe stress that apnea places on the cardiovascular system. A new study (Genuardi et al., 2019) has provided evidence that short sleep alone, in the absence of sleep apnea, may also increase significantly the risk of atrial fibrillation.
One of the motivations for the study was that known risk factors for atrial fibrillation can only explain about half of the population risk observed. This study was specifically designed to investigate the association between sleep duration and the prevalence (“the proportion of a population who have a specific characteristic in a given time period”) and incidence ("a measure of the number of new cases of a characteristic that develop in a population in a specified time period") of atrial fibrillation.
This research looked at the most recent sleep study of all adult patients at the University of Pittsburgh Medical Center sleep laboratories who underwent full-night diagnostic polysomnography from March of 1999 to December of 2015. This yielded 30,061 patients, with an average age of 51 years. Women made up 51.6 percent of the sample.
Using EKGs that were a part of the sleep study, 404 patients were identified as having atrial fibrillation. The researchers used measured sleep duration during the polysomnograms and found that short sleep was an independent risk factor for both prevalent and incident atrial fibrillation. Those who slept less than 3 hours were most at risk, followed by those who slept 3 to 4 hours, as compared to patients who slept 6 or more hours.
To investigate the impact of short sleep on the incidence of atrial fibrillation, 27,589 patients that had not shown atrial fibrillation during the sleep study, did not have any evidence of atrial fibrillation in their medical record, and that had not been lost to follow up, were followed for an average of 4.6 years. During follow up, 1,820 new cases of atrial fibrillation were identified. Patients with shorter sleep had significantly shorter time before developing atrial fibrillation.
In summary, every hour less of sleep was associated with a 17 percent greater risk of having atrial fibrillation and a 9 percent greater risk of developing atrial fibrillation. It is important to note that this risk was found after taking into consideration the known risk of sleep-disordered breathing.
The effects of short sleep may contribute to this increased risk through a number of known mechanisms including increased risk of obesity, diabetes, and hypertension; increased cardiac electromechanical delay; increased sympathetic nervous system activity; and activation of proinflammatory systems.
The primary limitation of this study was that it looked at total sleep time based on a one-night sleep study and may not have fully captured the average sleep of some of the patients in the study. This is a limitation of all laboratory-based sleep research. On the other hand, the use of objectively recorded sleep helps eliminate some of the problems in research based on the self-report of participants.
As the authors point out, poor sleep is an increasing problem and has significant importance for population-wide health. Unaddressed by this study was the potential benefit of treating sleep problems such as insomnia and insufficient sleep, and the effect treatment would have on the incidence and prevalence of atrial fibrillation.
Clearly, further evidence is accumulating that getting good sleep is imperative to having good health. Poor sleep affects the heart negatively and increases the risk of heart disease.
So, as we look to a new year, be sure to be good to yourself! Focus on getting a good night’s sleep—every night of the new year!
References
Epstein, L.J. & Mardon, S. (2007). A Good Night’s Sleep. New York: McGraw Hill.
Genuardi, M.V., Ogilvie, RP, Saand, A.R., DeSensi, R.S., Saul, M.I., Magnani, J.W., Patel, S.R. (2019). Association of short sleep duration and atrial fibrillation. Chest, 156 (3), 544 – 552. DOI: https://doi.org/10.1016/j.chest.2019.01.033
Jacobs, G. (1998). Say Goodnight to Insomnia. New York: Henry Holt and Company, LLC.
Somers, V.K. & Javaheri, S. (2017). Cardiovascular effects of sleep-related breathing disorders, in Kryger, M, Roth, T, & Dement, W.C. (Eds.), (2017). Principles and Practice of Sleep Medicine sixth edition, Philadelphia: Elsevier, Inc.
