The Greek hero of the Trojan war, Achilles, had only one vulnerable area on his body, his heel. Similarly, modern humans also have a vulnerable part of the our anatomy, the upper airway, which simultaneously accommodates for breathing, swallowing, and speaking. The ability to talk, however, came at a price.

Evolutionary biologists have stated that speech and language development was detrimental to our health. Overdevelopment of our speech structures compromised our ability to breathe and swallow. This is why compared to other mammals, only humans have so many problems with breathing and swallowing, making us uniquely more prone to choking and dying.

Complex speech and language ability is possible through a process called laryngeal descent. In non-human species, the soft palate overlaps with the epiglottis, which is the hood-like cartilaginous structure that makes up the upper part of the voice box. As the epiglottis separates away from the soft palate, human speech becomes possible. This process leads to an air-filled space called the oropharynx, which is present only in humans. If you say ahhhh while looking in a mirror, it’s the space behind the tongue, below and behind the edge of the soft palate, and between the sidewalls of the back of your throat.

Human infants are also born with the soft-palate overlapping the epiglottis, giving them the ability to suckle and breathe at the same time. At around 2-4 months, the voice box, along with the epiglottis, separates away from the soft palate, and the infant goes from being an obligate nose breather to being able to breathe through the mouth as well as the nose. Not too coincidentally, this transition period is also when the rate of sudden infant death syndrome (SIDS) peaks.

Once the larynx is completely descended, the more the tongue can fall back into the oropharynx and obstruct breathing, especially when you’re sleeping on your back and when you’re in deep sleep, due to further muscle relaxation. Most healthy adults don’t have too much difficulty breathing at night, even on their backs, but problems begin to arise if there’s any additional temporary or permanent narrowing of the air passageways, such as from colds, allergies, nasal congestion, weight gain, or even menopause.

Regardless of these impediments, speech and language allowed humans to develop impressive cultures, civilizations and technological advances, especially in the past 100 years. However, as a consequence of  “modernization,” our already narrowed airways became even more compromised due to a major shift in our diets and infant feeding habits.

Our jaws are genetically predetermined to reach a certain size by the time we’re adults, and constant stimulation and proper use of the tongue, mouth, teeth, and lips is instrumental in promoting optimal growth and maturity. With modern diets, we’ve gone from chewing, grinding, ripping and shredding our food which is taken naturally from the land, mountains or oceans, to soft, processed foods, with less nutritional value. Cultures that chew hard foods are found to have straighter teeth. Furthermore, bottle-feeding has been proposed to promote crooked teeth, due to the unnatural sucking and swallowing mechanisms created by the artificial nipple.

We now have an epidemic of malocclusions with braces being a rite of passage for most of our children. It’s almost “normal” for children and young adults to have high-arched hard palates, recessed chin lines and a deviated nasal septum due to midface underdevelopment. Although not as common as it was in the old days, multiple teeth beyond the wisdom teeth are still being extracted to promote more optimal bites and straighter teeth. This makes the jaws even smaller.

Despite the smaller jaw structures, the soft tissues such as your tongue, soft palate and nasal septum grow to their normal sizes and crowds the upper airway that’s already compromised from the above stated reasons. This is why many people can’t sleep on their back, and some can only sleep on their stomachs. Serious sleep problems can occur if you’re suddenly forced to sleep on your back, such as after an accident or an operation.

These episodes of breathing obstruction can happen in any stage of sleep, but are more likely in deeper levels of sleep, and especially in REM sleep, when your muscles are most relaxed. Once you obstruct (fully or partially) during inhalation, and the pause lasts for more than 10 seconds, then it’s called an apnea or hypopnea. If you underwent a sleep study, you’ll need more than 5 apneas or hypopneas per hour to say that you have obstructive sleep apnea. However, if you stop breathing 25 times per hour, but each episode is only 1-9 seconds long, then you won’t have any apneas or hypopneas. In general, the heavier you are, the more likely your breathing pauses will last longer. Most people also tend to wake up at 90 to 120 minute intervals or at the same time every night, since that’s the interval for one sleep cycle. As the end of one of these cycles, you reach deeper levels of sleep.

Having multiple obstructions and arousals during sleep that don’t meet the criteria for obstructive sleep apnea is called upper airway resistance syndrome, which presents with various other symptoms such as fatigue, depression or anxiety, headaches, low blood pressure, cold hands, hypothyroidism, and even various gastrointestinal symptoms. Not getting continuous deep sleep has been shown to literally wreak havoc on every system in your body. Think about how you would feel if you’re in a haunted house or being chased by a tiger. You’ll be on edge, hypersensitive, or over-react to relatively normal situations. Not getting good quality sleep can make you feel this way all the time. Lastly, poor sleep has been shown to promote weight gain— increased fat cells in your throat can then aggravate your breathing problems. Many people with upper airway resistance syndrome have parents that have classic obstructive sleep apnea.

It’s been shown that you can be young, thin, female, and not snore, and still have significant obstructive sleep apnea. Physicians must get rid of the idea that you have to be an overweight, big-necked man who snores heavily to have obstructive sleep apnea. Even if you do fit the classic stereotype for someone with sleep apnea, this diagnosis is rarely made. A recent study from Sweden showed that 50% of women aged 20-70 had significant levels of obstructive sleep apnea. If you extrapolate this figure to a more obese US population, and knowing that men have much higher rates of obstructive sleep apnea compares with women, you can see the frightening implications. Untreated obstructive sleep apnea has been strongly linked to increased risk of hypertension, diabetes, heart disease, heart attack, stroke, early death, and even cancer. 

I’m not saying that everyone has obstructive sleep apnea. What I am saying is that being susceptible to sleep-breathing problems is a normal part of being a modern human being, whether or not you have obstructive sleep apnea. Even if you’re totally normal and sleep well, think about the last time you had a bad cold. What happened to your sleep? Did you toss and turn all night? Think about a flimsy straw as you pinch the tip. What happens to the middle part?

The next time you hear your bed-partner or young child snore, or if you have chronic nagging health problems that just won’t go away, think first about addressing an underlying sleep-breathing problem. Similar to Achilles’ fate, this vulnerability in our anatomy can lead to numerous chronic illnesses, or even death.

Steven Y. Park is Assistant Professor of Otorhinolaryngology, Albert Einstein College of Medicine. He is author of Sleep, Interrupted: A Physician Reveals The #1 Reason Why So Many Of Us Are Sick And Tired.