Tag Archives: sleep apnea

History of Sleep

Galen

History of Sleep
While it seems obvious that humans have slept throughout their history, the way they did so in the past might be different from how we sleep today. For example, in his famous Oddysey written around 800 BC, Homer writes about people having two very distinct periods of sleep at different times of the 24 hour cycle. About three hundred years later, the Greek Alcmaeon observed that blood seemed to be draining from the vessels as we sleep, and assumed that this was a cause of it. Similarly, around 400B.C., Hippocrates noted that bodies cool during sleep and that sleep was therefore characterized by blood retreating from the periphery. Not long after that, Aristotle suggested that sleep was brought on by the warming of the body through digestion. Of course, such an observation would be heavily influenced by what one was eating and drinking and certainly rich foods and plentiful amounts of wine could have people nodding off in no time.

Up until about 162 A.D., the view was that the heart, not the brain, was the center of influence from which all bodily actions were controlled. It was Galen who suggested that the brain was the body’s control center and not the heart, leading to sleep theories that were centered on brain rather than heart activity. Subsequent research suggests that the ancients weren’t totally wrong about the heart. It turns out that there are about 50,000 neurons (brain cells) in the heart that connect with the brain. And there are 500 million neurons in the gut, so perhaps Aristotle’s connection between sleeping and eating wasn’t entirely off the mark.

Despite Descartes’ effort during the Renaissance to divide mind and body, much of the subsequent work focused on the brain’s control of the sleep process. In 1650, Dr. Willis identified the functions of different parts of the brain; in 1929, Hans Berger invented the EEG, which opened the study of the brain and its activity. Later, various areas of the brain were identified with the specific functions of sleep.

Specific identification and treatment for sleep disorders emerged in the twentieth century. In 1903 the first sleeping pill was introduced and in 1930 the first stimulant treatment for narcolepsy was developed. Restless Leg Syndrome (RLS) was first described by a Swedish doctor in 1945 and other conditions were subsequently diagnosed; for example, Dr. Schenk and colleagues first reported on a group of patients who didn’t demonstrate the usual muscle paralysis when in REM. In the last seventy years, there has been even more research, which has been able to identify the different stages and phases of sleep.

Nathaniel Kleitman was one of the pioneers of sleep research, with an interesting personal history. Arriving in New York as a penniless 20-year-old in 1915, he went on to get a PhD and conduct some of the earliest research on sleep and the brain. Using a crude EEG machine that used about half a mile of paper each time it ran a sleep test, Kleitman noticed the different stages of sleep, especially dreaming sleep. In a 1953 paper, he and his colleague, Eugene Aserinsky, called this stage of sleep “Rapid Eye Movement.” Kleitman, who lived to be 104, was fascinated by the concept of wake/sleep cycles and even conducted research on the effects of sleeping in caves and submarines.

One of Kleitman’s proteges, William Dement, continued the tradition of researching the brain and sleep using EEG technology. Dement was interested in sleep dysfunction and has contributed enormously to the diagnosis and treatment of sleep disorders. He is widely considered the father of sleep medicine. He launched what is now known as the American Academy of Sleep medicine and served as president for twelve years. Dement also played bass as a jazz musician and has even played with musical greats, Ray Charles and Quincy Jones.

Dement formed the Stanford University Sleep Disorders Clinic which has been the home to a great deal of important sleep research and some other very influential researchers. One of these is Christian Guillemenault, a prolific researcher, who has written more than 600 academic papers. His most noted work has been on the subject of sleep apnea. He co-opted cardiologists to measure and observe blood pressure and cardiac function in people who have what we now know as sleep apnea. In fact, Guillemenault was one of the first to use the term ‘obstructive sleep apnea’ and was the first to use tracheostomies to free the airways, both providing relief to sufferers as well as convincingly demonstrating the relationship between apnea and cardiovascular function.

Despite the work of these pioneers, sleep medicine research and literature lagged behind that of the other key lifestyle behaviors, like nutrition and exercise. It is only in the past decade has there been a recognition of the importance of sleep, elevating it to a science more in keeping with its importance.

It’s good to breathe

Obstructive sleep apnea can be quite dangerous when not treated.  Restricted airflow which occurs repetitively in individuals with sleep apnea stresses the body in several ways.  We know that people who suffer from obstructive sleep apnea have a higher risk of high blood pressure, stroke, irregular heart rhythms, elevated blood glucose levels, car accidents and even sudden cardiac death.  In addition, people with sleep apnea often feel tired, complain of non-restorative sleep and have a poor quality of life.  Having untreated sleep apnea does not necessarily mean that an individual will ever suffer these ailments, but it does raise the risk.   The more severe the sleep apnea, the higher the likelihood of ever suffering from one of these entities.

Untreated sleep apnea results in these ill effects for two main reasons.  First of all, the oxygen levels dip which stresses the body. The second reason is that sleep apnea results in fragmented and poor quality sleep.

When people don’t breath well at night,  oxygen levels repetitively dip resulting in bodily stress.  As most people are aware, our body tissues need adequate oxygen for optimal function.  It can thought of as a stress test every night.  When a person’s upper airways narrow, airflow is limited and oxygen levels drop.    Most people’s oxygen levels remain at 97-100%.  Associated with apnea events, oxygen levels drop by at least 3%.  It is not uncommon for oxygen levels to drop even further.  Individuals with severe sleep apnea commonly have drops of their oxygen levels into the 70-80% range.  I have seen patient’s with oxygen levels dipping into the 50s%!     When the tissues are starved of adequate oxygen, the risk of heart attack and stroke increases.  The sympathetic nervous system is activated which results in elevated blood pressures with frequent surges in blood pressure and heart rate.   In addition, inflammatory mediators are released which can further damage tissues.

Sleep apnea also results in fragmented  and poor quality sleep.  After a good night’s sleep, a person should feel refreshed and ready for a full day’s activities.  Optimal sleep should last 7-8 hours in adults during which a person cycles through stages of sleep.   There should be 3-4 sleep cycles during which a person transitions from light sleep, to deep sleep and then into REM sleep.  We call this sleep architecture.  Each stage of sleep is associated with important bodily functions like memory consolidation, hormone secretion and clearing of accumulated waste products.   If an individual’s sleep is disrupted by sleep apnea, sleep architecture becomes fragmented and the full benefits of sleep are not achieved.  The breathing events associated with sleep apnea frequently cause arousals.  Essentially, arousals are ‘brain awakenings’ which disrupt sleep architecture.    For example, a person with moderate or severe sleep apnea will commonly have more than 15 arousals per hours which prevents them from entering the restorative stages of sleep such as deep sleep.  This is why a patient with sleep apnea will commonly state that they never feel like they slept.

Indeed, it is good to breathe.  This article explains why obstructive sleep apnea leads to an increased risk of cardiovascular problems, as well as excessive daytime sleepiness.