Tuesday, August 14, 2012
This is the tale of how an Australian man with a vacuum cleaner fixed a mistake in evolution.
It begins in the late 1970s. Colin Sullivan is a physician in the respiratory unit at Sydney’s Royal Prince Alfred Hospital. There, he treats patients who have problems breathing. The most common complaint, by far, is snoring. Sullivan knows better than most doctors in his field that snoring is often a sign of a serious disorder known as sleep apnea. The disorder had been identified only about a decade earlier.
Patients with sleep apnea experience a strange nightly sensation that brings the body disturbingly close to death. First, the throat closes randomly throughout the night, choking off the body’s air supply. This puts in motion a cascade of increasingly bad side effects. As if on a seesaw, the lack of air causes the oxygen levels in the blood to plummet and the blood pressure to jump. The lips and skin start to turn blue. Air may not come into the lungs for up to a minute. And for some patients, the heart stops beating for almost 10 seconds at a time.
Eventually, the brain gets the urgent message that the body is choking. The brain jolts awake, and the body instinctively gasps for air. Yet as soon as the airway is clear, the brain immediately falls back to sleep. That’s when the cycle starts again. It is all so quick that it can happen more than 20 times an hour, all night long, without the sleeper remembering it the next day. Someone lying next to him or her, however, can hear this process at work: When the rhythmic sawing of a snorer’s breath pauses and then becomes a hard ghhack-ghhack-ghhack, it’s most likely the body frantically clearing its airway.
Sleep apnea was discovered when a group of American physicians noticed that some obese patients complained of overwhelming fatigue and would drift asleep unintentionally. With a literary flourish, they named the condition Pickwickian syndrome after a character who falls asleep standing up in Charles Dickens’s first novel, The Pickwick Papers. Doctors incorrectly attributed the sleepiness to a combination of excess weight and abnormally high levels of carbon dioxide in the blood. It was only later that science understood sleep apnea to be a common breathing disorder caused by the position of the tongue and tissues of the throat. It was then given the name apnea, from the Greek word for breathless.
Sleep apnea was on the frontier of sleep medicine in the late 1970s. Sullivan had recently returned from a fellowship in Toronto, where he spent three years studying the breathing patterns of dogs while they slept. English bulldogs, pugs, and other breeds with pushed-in faces are the only animals besides humans that experience sleep apnea. The years spent working with dogs gave Sullivan an idea. Once back in Sydney, he devised a mask that fit over a dog’s snout. The mask continuously pumped in air from the surrounding room, increasing the air pressure in the throat and preventing it from closing up.
Experiments with dogs suggested that the steady flow of air dramatically improved sleep. All Sullivan needed was a human to try it out on.
In June of 1980, he found one. A man walked into the hospital with such a severe case of sleep apnea that Sullivan recommended an immediate tracheotomy. This procedure, which consisted of making a hole in the throat to allow a person to breathe without using the nose or mouth, was one of the few approved treatments for sleep apnea at the time. It required a permanent, quarter-size opening in the neck, however, and was quite painful.
The patient refused the tracheotomy. But he was happy to volunteer as a test patient for Sullivan’s air-pressure machine. Sullivan built a test model that afternoon. He grabbed the engine out of a vacuum cleaner and attached it to a handful of plastic tubes. He then took a diving mask and coated the edges with a silicone sealant that prevented air from leaking out of it. Soon, he had a system that allowed him to pump air through the mask at a controlled pressure. Sullivan found an empty room in the hospital and set up equipment to monitor the patient’s breathing and brain waves, which would tell him what stage of sleep the man was in. The patient was hooked up to the monitors, put on the mask, and fell asleep almost instantly.
He began experiencing sleep apnea within a few minutes. Sullivan then slowly started to increase the pressure in the air flowing through the mask and into the patient’s airway. Suddenly, the apnea stopped. The patient began breathing normally. As Sullivan watched in amazement, the patient instantly went into deep REM sleep—a rare phenomenon suggesting that his brain had been starved of restorative sleep. Sullivan then slowly decreased the pressure of the air flowing through the mask. The apnea returned. Sullivan rapidly went through several cycles of increasing and decreasing the pressure. He found that with the machine’s controls alone, he could effectively turn the patient’s sleep apnea on and off.
The machine worked. The next question was whether its benefits would last all night. Sullivan left the settings on the machine at a level where the patient was free of sleep apnea. Then he waited. For about seven straight hours, the patient was in abnormally intense, deep sleep. When he woke up the next day, he told Sullivan that he felt awake and alert for the first time in years.
A study in 1994 found that about 10 percent of women and 25 percent of men have difficulties breathing in their sleep. These numbers climb as a person gets older, so that as many as 1 out of 3 elderly men have at least a mild case of sleep apnea. All told, about 20 million Americans have the disorder.
Its cause could simply be the trade-off that the human body makes for having the ability to speak in a complex language. A short tour of fossils illustrates this point. If you were to look at a Neanderthal’s mouth, you might think that its descendants would have been the ones to survive over the long run, considering their jawbones were larger and stronger than our own. Plus, with extra room in their mouths, Neanderthals never experienced the pain of impacted wisdom teeth. Homo sapiens differed from Neanderthals by developing a flatter face, a smaller jawbone, and a tongue that descends deeper into the throat than in any other mammal. With this new hardware, humans were able to move beyond making simple grunts. Those first, complicated sounds uttered by Homo sapiens soon developed into language.
But the positioning of the tongue in the Homo sapiens mouth complicates the acts of eating, drinking, and breathing. Food could literally go down the wrong pipe, a biological problem unique to modern humans. Darwin noted “the strange fact that every particle of food and drink we swallow has to pass over the orifice of the trachea with some risk of falling into the lungs.” The longer tissues of the soft palate at the back of the throat made it possible for the airway to become blocked after a routine exhalation, which could start the cycle of sleep apnea. In the mid-1990s, researchers in Japan found that slight changes in the size and position of the pharynx at the back of the throat drastically increased the likelihood that someone would develop a breathing disorder during sleep. The shape of a person’s neck and jaw can also be a factor. A large neck, tongue, or tonsils, or a narrow airway often signal that a person will develop sleep apnea because of the increased chance that breathing will become blocked during the night.
And yet the physicians who first recognized sleep apnea were half right when they assumed that the disorder was a side effect of obesity. Sleep apnea is a flaw that is part of the blueprint of the human body, and excess fat often teases it out. The chances of developing sleep apnea go up with weight because the tissues in the throat become enlarged, making it more likely that they will obstruct the airway during sleep. For some patients, losing weight alone can solve the problem. Other changes in behavior—like drinking less alcohol, cutting back on smoking, sleeping on one’s side instead of on the back, or doing exercises or playing musical instruments that build up the muscles in the throat—can also help.
Breathing masks like those manufactured by ResMed, the company Sullivan co-founded in 1989 after developing simpler prototypes of his machine, are the most common medical treatment for sleep apnea, but they aren’t for everyone. Some patients never get used to the awkward sensation of sleeping with a mask on their face or never become comfortable with breathing in the cold air that is continuously pumped into their mouth throughout the night. In the long term, patients with mild sleep apnea wear the masks between 40 and 80 percent of the time, according to various studies. There is also a social stigma that complicates treatment. Some patients with sleep apnea decide not to use a continuous positive airway pressure, or CPAP, machine because they are worried that it will make them less attractive to the person they are sharing a bed with. In an online support group for patients with sleep apnea, a man wrote that he was “feeling like I am going to be Darth Vader if I have to wear one.” A woman wrote that her husband “fought it, cried, said he is defective, said he would prefer to put a gun to his head then wear one of those things.” Another wrote that “I’ve yelled that I feel like a freak to my husband way too many times this fall.”
Dental devices are typically the next choice. These aren’t as effective as CPAP machines for severe sleep apnea, but they may be easier for some patients to use, especially those who have to travel frequently. One of the most popular looks like a sports mouthguard. It forces the lower jaw forward and slightly down to keep the airway open. Another device holds the tongue in place to prevent it from getting in the way. Surgery is the last option. One procedure, called an uvulopalatopharyngoplasty, consists of removing excess soft tissue from the back of the throat. Its long-term success rate is only about 50 percent, and it can lead to side effects such as difficulties swallowing, an impaired sense of smell, and infection. It is also extremely painful. Few medications have been shown to help sleep apnea and may in fact make the problem worse. Sleeping pills and tranquilizers, for instance, can make the soft tissues in the throat sag and obstruct the airway more than they would otherwise.
In 2000, four separate studies found conclusive evidence that sleep apnea was associated with increased rates of hypertension. Left untreated, patients with sleep apnea are at a greater risk of developing kidney disease or vision problems, or having a heart attack or stroke. Those studies helped convince government insurance programs such as Medicare, Medicaid, and the British National Health Service to pay for a portion of the cost of each ResMed device, which can be several-thousand dollars if a patient were to buy it out of pocket. Sleep labs across the country now conduct overnight tests in which patients who are suspected to have sleep apnea are hooked up to equipment that monitors their hearts, breathing patterns, and brain activity, as well as the number of times they wake up throughout the night and how often they move their limbs.
As scientists began to understand sleep apnea in more depth, they started to see it as the foundation for serious illnesses affecting the mind. In one study, researchers at UCLA conducted brain scans of patients with long histories of sleep apnea and compared them with the scans of control subjects who had normal sleep patterns. The investigations focused their inquiry on the mammillary bodies, two structures on the underside of the brain so named because they resemble small breasts. Mammillary bodies are thought to be an important part of the memory and have long been associated with cases of amnesia. This memory center of the brain was 20 percent smaller in patients with sleep apnea. Had a doctor looked at a patient’s brain scan alone, it would have suggested severe cognitive impairment: A similar shrinkage in the size of the mammillary bodies is found in patients with Alzheimer’s disease or those who experienced memory loss as a result of alcoholism. It was the first indication that sleep apnea leaves a permanent scar beyond the daily difficulties of focus and attention that come with sleepiness.
A study published in the Journal of the American Medical Association supported this conclusion. Kristine Yaffe, a professor of psychiatry at the University of California-San Francisco, led a study that recruited nearly 300 elderly women who were mentally and physically fit. The average age of the subjects in the study was 82. Each woman spent a night in a sleep lab, and Yaffe found that about 1 in every 3 met the standard for sleep apnea. Yaffe re-examined each woman five years later. The effects of age on the mind seemed to depend on the quality of sleep. Nearly half of the women with sleep apnea showed signs of mild cognitive impairment or dementia, compared with only a third of the women who slept normally. After controlling for factors such as age, race, and the use of medicines, Yaffe found that the women with sleep apnea were 85 percent more likely to show the first signs of memory loss. The frequent interruptions in sleep and the reduced oxygen in the brain may reduce the brain’s ability to form and protect long-term memories.
Sleep apnea and weight are not problems limited to the United States, a fact that hasn’t been lost on companies like ResMed. The spread of Western fast-food companies like McDonald’s, Kentucky Fried Chicken, and Pizza Hut to emerging countries such as China and India may be the greatest growth engine for ResMed. Simply put, more fat in the bodies of the world’s population equals a larger number of sleep apnea cases, creating a larger customer base for ResMed’s products. “Genetically you’re still engineered for a low-calorie, low-fat diet,” Kieran Gallahue, CEO of ResMed at the time I visited the company’s headquarters in 2010, told me. “That’s what your body has been optimized for over centuries. Boom, you introduce burgers, and your body is not going to handle it. One of the outcomes is going to be a skyrocketing in the prevalence of sleep-disordered breathing.”
By David K. Randall