Is sleep healthy, or hurtful?

Methought I heard a voice cry, "Sleep no more!
Macbeth does murder sleep!" the innocent sleep,
Sleep that knits up the ravelled sleave of care,
The death of each day's life, sore labor's bath,
Balm of hurt minds, great nature's second course,
Chief nourisher in life's feast.
[Shakespeare, Macbeth, Act 2, Scene 2] 

Most sleep heals and restores. But sometimes, sleep hurts.

People who have a specially troubled kind of sleep may run a much greater risk of high blood pressure, heart attack, stroke, and the worsening of other medical conditions.  

Sleep apnea is a common disorder that causes a sleeper to pause, or even stop, breathing. Apnea pauses may occur 5 to 30 times an hour, and last from a few seconds to minutes. A loud snort or gasp signals the return to normal breathing, and may or may not wake the sleeper.

The most common type of sleep apnea is obstructive sleep apnea, in which the sleeper's airways narrow or become blocked. The resulting recurrent oxygen deprivation to the brain from apnea, literally "holding breath," taxes both the brain and the cardiovascular system. 

The effects of sleep deprivation, such as fatigue, depression, and loss of mental capacity, are relatively well-known. But the most significant effects of apnea are on the heart and circulatory system, according to Dr. Douglas Bradley, director of the Centre for Sleep Medicine and Circadian Biology at the University of Toronto.  

The frequent drops in oxygen levels and interrupted sleep trigger the release of stress hormones, which then increase the heart rate. In effect, the sleeper is having a harmful, unconscious workout. As a result, Dr. Bradley said, apnea sufferers run elevated risks of stroke (rupture of blood vessels in the brain), heart failure, and heart attack: a four times greater risk of stroke, and more than twice the risk of heart failure.  

Speaking at a recent "Café Scientifique" in Niagara-on-the-Lake organized by Institute for Circulatory and Respiratory Health and Brock University, Dr. Bradley suggested that treating apnea may prove also to be a very useful way of reducing or preventing heart attacks and stroke.

Dr. Bradley noted that over 70 percent of stroke patients in treatment also have sleep apnea. Treating the sleep apnea improved their recovery outcomes. This association between stroke and apnea prompted Dr. Bradley and others to begin to look more closely at how sleep might affect circulatory and respiratory health.

Early research suggests that sleep -- perhaps beyond its disorders, such as apnea -- is profoundly important to respiratory and cardiovascular health. Monitoring the quality of sleep a person gets might give an early indicator of underlying disease, while improving sleep might provide a way of preventing disease.

The healthiness of sleep is receiving serious consideration. Research into how sleep impacts respiratory and cardiovascular diseases, metabolism, and obesity has been placed among the top eight research priorities for 2006-2010 by the Institute for Circulatory and Respiratory Health, one of the network of Canadian Institutes of Health Research.

If diagnostic or preventative health tools can be made from the expanded understandings of sleep, then the way sleep "knits up the ravelled sleave of care" may get an even more beneficial meaning.

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Snoring is more than annoying

Common symptoms of sleep apnea include:

- disordered breathing (choking, gasping or snoring during sleep)
- recurrent awakenings, accompanied by shortness of breath
- unrefreshing sleep, daytime fatigue and impaired concentration
- morning headache
- difficulty staying asleep, or insomnia

Diagnosis of a serious sleep disorder is done with the aid of a polysomnogram (PSG). The PSG monitors many body functions including brain (EEG), eye movements (EOG), muscle activity or skeletal muscle activation (EMG), heart rhythm (ECG), and breathing function or respiratory effort during sleep.  

Source: Public Health Agency of Canada
[http://www.phac-aspc.gc.ca/publicat/2007/lbrdc-vsmrc/sleep-sommeil-eng.php]