Kathleen is a 50-year-old mother of three who came to see me for worsening snoring, severe fatigue, and lack of focus and concentration for the past 3 months. Her exam was typical for OSA—she had very narrow airways. When questioned about any major life changes she noted that after her children moved out she decided to enroll in night classes at the local community college about 4 to 5 months ago. This meant that she would have to go straight to classes after work. She then got home later at night and she ate just before going to bed. She noted that her father snored like a chainsaw and underwent heart bypass surgery at age 60.
She was also distressed about gaining an unexpected 10 pounds in the past few months and always craved donuts and chocolate. She was so stressed and wired after dinner that she had difficulty falling asleep. Occasionally, she drank some red wine to help her to fall asleep.
In sleep medicine, we talk about the 3 Ps of insomnia: predisposing, precipitating, and perpetuating factors. (1) factors for insomnia include biological, psychological, and social factors. Precipitating factors include medical or psychiatric illness or a stressful life event. Perpetuating factors include excessive time in bed, napping, or conditioning.
Similarly, the same concept can be applied for obstructive sleep apnea. Predisposing factors include evolutionary and developmental factors, your genes and family history, nasal congestion, diet, and infant feeding habits. Precipitating factors can be weight gain, infections, allergies, normal development and aging, such as adolescence and pregnancy, trauma, and major life/work changes. Some perpetuating factors include bad habits (a form of conditioning) such as eating late, staying up late, or using the computer at night. Throughout the rest of this book, I will revisit the three Ps repeatedly where appropriate.
Kathleen’s major predisposing factor was her family history. She inherited her father’s upper airway anatomy—she mentioned that she had her father’s teeth. As a teenager, she underwent braces for very crooked teeth, with two upper jaw bicuspids removed. She normally likes to sleep on her sides, but due to a shoulder injury 6 months ago, she started to sleep more on her back. Only recently is she sleeping on her side again.
She is also in her perimenopausal years where progesterone levels start to go down very slowly. One of the benefits of progesterone is that it helps to increase upper airway muscle tone. As you slowly begin to lose progesterone in your early 40s, it is only natural that your sleep quality will go down. All these factors predisposed her for developing OSA.
Notice that she also gained some weight. This is one possible precipitating factor. Weight gain is a major risk factor for developing OSA. Eating later at night before bedtime can also increase reflux episodes and obstructed breathing, leading to less efficient sleep. Less efficient sleep is known to cause weight gain. She also began to sleep more on there back for a few months due to her shoulder injury. The other major trigger is that she started taking night classes and had to shift her dinner to a much later time.
Her likely perpetuating factors are behaviors and habits that promote less efficient sleep and more obstructed breathing. Any degree of sleep deprivation can cause appetite changes that cause cravings for sugary, fatty, or starchy foods, which can cause weight gain. Sleep-deprived people get very hungry just before bedtime. Having something in your stomach may help you to fall asleep faster, but it will lower your overall sleep efficiency. Gaining weight will then narrow your throat, causing more obstructions and more reflux, leading to more obstructed breathing.
Drinking alcohol to fall asleep faster may help initially, but alcohol will relax throat muscles even more and cause more obstructions. The vicious cycle continues. Notice that sometimes, the predisposing, precipitating and perpetuating factors can overlap to various degrees. In most cases, however, if you take the time to probe into the patient’s history, each of the three factors will become clear.
Anything else that causes your sleep quality to diminish can act as a predisposing, precipitating, or perpetuating factors, depending on the timing (how suddenly it happens vs. chronic nature) and intensity. For example, eating late just before sleep for many years can lower your sleep efficiency, but you may sleep well. But suddenly getting 2 hours less sleep may be enough to trigger daytime symptoms such as brain fog and fatigue. But if you normally eat 4 hours before going to bed, and suddenly are sleep deprived 2 hours, you may not be as affected severely.
Here’s another example: If you normally eat early and get by on 8 hours of sleep, but then you start night classes and have to eat really late, then your sleep quality may go downhill even if you sleep for 8 hours. In these situations, eating late can be a predisposing factor, a precipitating factor, or even a perpetuating factor. This is why spending time to get a good history by the physician is so important.
Predisposing Factors / Why Humans Choke
There are a number of different predisposing reasons for why you (and all other modern humans) may have a sleep-breathing problem.
In my book, Sleep Interrupted, I describe my sleep-breathing paradigm, which states that all modern humans are predisposed to breathing problems at night, and that all of us are on a continuum where only the extreme end of the spectrum is called obstructive sleep apnea.
A major reason why all humans have potential breathing problems at night is due to our upper airway anatomy. Evolutionary biologists and comparative anatomists say that our ability to talk and communicate makes us more susceptible to breathing and swallowing problems. With a few exceptions (such as flat-faced dogs), only humans can choke and die. Unfortunately, this happens quite often.
Dr. Terrance Davidson reviewed this topic in his paper, The Great Leap Forward: the anatomic basis for the acquisition of speech and obstructive sleep apnea.(2) He mentions three important anatomic features that lead to so many cases of choking and swallowing problems in modern humans compared to lower primates.
This is the process where during evolutionary development, the mid-face and jaw structures rotate back and underneath the slowly enlarging brain cavity.
2. Forward migration of the foramen magnum
Along with klinorhynchy, the opening in the base of the skull that allows your spinal cord to pass into your spine moves forward.
Notice how the combination of these two factors narrows the throat, compressing the upper airway from the front and back.
3. Laryngeal descent and loss of soft palate–epiglottis lockup
Lower primates (as well as human infants) have their voice box (larynx) positioned behind the tongue, with an overlap of the soft palate and epiglottis (top-most part of the voice box).
This is what allows human babies to suckle and breathe at the same time while feeding on the mother’s breast. In infants, the voice box (which includes the epiglottis) begins to drop and separates away from the soft palate at around age 3 to 4 months. Full separation occurs with the onset of adulthood, leading to a space called the oropharynx.The voice box is now positioned below the tongue, which allows for complex sleep and language development. Increased pliability and mobility of the soft tissues of the mouth and throat is needed for humans to communicate using speech.
This unique anatomy also allows the tongue to fall back into the oropharynx, leading to potential breathing and choking problems. (see above figure) This transition period can potentially lead to a potentially life-threatening situation called SIDS, or sudden infant death syndrome. I’ll cover this in more detail in the chapter on children.
When Your Voice Box Drops
In medical school, I was taught that the human voice box stops dropping when you’re fully grown. However, I recently came across a reference (see figure below) that has huge implications for human development and aging. Notice that from age 20 to 80, the voice box continues to drop another full vertebral body height. This means that as the voice box drops, the floppy tube of the throat becomes longer and the tongue become more collapsible. This concept implies that humans will have more breathing problems as we age. If you also start to lose teeth as you get older, your jaws will get even smaller. If you happen to put on weight, then the fat cells in your throat get bigger, and your throat becomes even more narrow.
A number of studies have found that bottle-feeding, thumb sucking and pacifier use can aggravate crooked teeth, leading to the need for orthodontic intervention later on in life.(3) Crooked teeth means that the jaws did not develop fully enough to allow for all the adult teeth to have enough space to fit. Dr. Brian Palmer, one of my early mentors on this subject, states that the physical act of suckling from a mother’s breast is mechanically different than sucking from a bottle teat.
I remember one mother who had four children. All were exclusively breastfed for at least 6 months, except for one middle child who would not take his mother’s milk and was bottle-fed for the most part, and also sucked his thumb. The differences in their facial features were striking. The three children who were breastfed had wide facial features with well-developed jaws and no dental crowding, whereas the one boy who was bottle-fed had severe dental crowding and had a narrow, triangle-shaped face.
These concepts are more fully explained by Dr. Weston Price, a dentist who wrote the classic, Nutrition and Physical Degeneration, a book that is popular in the nutritional field.(4) He and his wife (a nurse) traveled the world in the first half of the 20th century and found that cultures that ate naturally off the land had wide facial features, straight teeth and essentially no cavities. As these cultures began to adopt Western, modern diets (soft, processed foods with refined sugars), their children’s teeth came in much more crooked with more cavities and narrowed dental arches. He found this phenomenon happening consistently in all the major continents, including Africa, South America, North America, and even Europe.
Oftentimes, the precipitating events are what brings patients into see me. Gradual weight gain over the course of weeks to months may have pushed you over the edge to begin snoring. Having a new job with increased demands with less time to exercises and eating later at night can also cause you to put on a few more pounds.
Any kind of infection or inflammation that causes swelling of your upper airway can aggravate sleep-breathing problems. Most colds or allergies go away within a few days or weeks, and your symptoms may improve over time. Sometimes, catching a cold, on top of gradual 20 pound weight gain over 6 months may precipitate apneas which will not go away.
A sudden change in your sleep position is a very common precipitating factor. Undergoing surgery, suffering from an injury or anything else that alters your normal sleep position can precipitate sleep-breathing problems. I’ve already mentioned what happens to patients admitted to the hospital after surgery, where you’re forced to sleep on your back.
Once a sleep-breathing problem is has been precipitated, it can go away after a period of time (such as after a cold, or temporary weight gain). But sometimes, various factors can perpetuate the vicious cycle. For example, poor sleep can alter your appetite to make you crave more sugary or fatty foods, which prevents you from losing weight, no matter how much you exercise. Using a new electronic device such as a room humidifier or new flat-screen TV that has extra-bright LED lights can disrupt your sleep quality. In a sense, this can be a precipitating event (aggravating new-onset insomnia) when you were previously sleeping well, or it can be a perpetuating factor, further aggravating issues only after you started to have sleep problems. Similarly. changing your sleep position can be either a predisposing, precipitating, or perpetuating factor.
Your Jaws, Your Life
Being overweight is a known major risk factor for obstructive sleep apnea. However, you can still have severe obstructive sleep apnea even if you are thin and do not snore. This is because having narrow jaws and dental crowding can predispose you to obstructive sleep apnea, even if you are not overweight. If a person with a smaller bony anatomy gains weight they will be more predisposed to obstructive sleep apnea. This is why certain ethnic groups have much higher rates of obstructive sleep apnea, despite lower rates of obesity. African Americans and Asians are found to have the highest rates of obstructive sleep apnea. It’s thought that this is due to their smaller facial bone structures, especially in the front to back dimensions of the mid-face (called the anterior cranial base). The ultimate size and shape of your jaws in relation to your optimal genetic blueprint will determine how predisposed or susceptible you will be to sleep-related breathing problems.
- Spielman, Arthur J. “Assessment of insomnia.” Clinical Psychology Review 6.1 (1986): 11-25.
- Davidson TM. The Great Leap Forward: the anatomic basis for the acquisition of speech and obstructive sleep apnea. Sleep Med. 2003;4(3):185–194.
- Viggiano D, Fasano D, Monaco G, Strohmenger L. Breast feeding, bottle feeding, and non-nutritive sucking; effects on occlusion in deciduous dentition. Arch Dis Child. 2004;89(12):1121–1123.
- Price, WA. Nutrition and physical degeneration. Price-Pottenger Nutrition Foundation, 2003.