Thank you for your reply, Dr. Luisi! That's an informative list of potential causes, including one I hadn't thought of before - braces (which I had)! As I mentioned in my original post, I'm most interested in what about our modern lifestyle causes OSA in non-obese people. For the purpose of this thought exercise, this assumes that our bodies evolved over hundreds of thousands of years, weeding out maladaptations to arrive at its current form, fairly well-adapted to live a long, healthy life on this planet, assuming conditions similar to most of human history, and not the environment and lifestyle we have been living for past couple/few centuries. Comments/questions, based on your list:
1. Born with large tongues and soft palates: Can't think of why this trait would have emerged and why it stays with us. Maybe because this trait doesn't become a cause of OSA as much until combined with aging, at which point humans have already reproduced, so this trait never had a chance to succumb to natural selection.
2. Enlarged tonsils and adenoids: It's possible that the amount of foreign substances in our modern air, both outdoors (pollution) and indoors (product off-gassing), would cause inflammation of these parts of our immune system. We also now migrate to completely different biomes than where our genetic ancestors evolved, meaning our immune system may have evolved for different natural airborne particles.
3. Allergies: Same as #2: an immune system reaction.
4. Deviated septum: Mostly caused by injury, and no reason for that to be higher with modern lifestyle. Possibly like #1, didn't have an impact until combined with aging.
5. Orthodontics: Now you're talking. There's an unnatural intervention of modern lifestyle that many of us have had, that had never been around while humans evolved. Which leads to me add a new theory, related to one I originally suggested:
6. Change to agricultural diet causing smaller jaws, weaker muscles: The advent of farming ~10,000 years ago meant that humans began eating softer foods that required less vigorous chewing than their hunter-gatherer ancestors. This has been confirmed in anthropology studies comparing jaw sizes of many agricultural vs. hunter/gatherer societies. Continuing this trend, impacted wisdom teeth became 10 times more common after the Industrial Revolution. This is why we now usually remove wisdom teeth - they don't fit in our small jaws. While jaw size has been the main focus of these studies, I'm thinking that tongue, jaw, and throat muscle tone would also suffer due to this dietary shift. Maybe I should give those anti-snoring throat/tongue exercises a try?
7. Aging: With our modern understanding of germ theory, vaccines, and life-saving trauma medicine and technology, the average human lifetime has increased since the Industrial Revolution. Maybe more of us are reaching an age in which sagging muscle tone, on top of any or all of the above reasons, is becoming an issue.
Thank you again, for listing so many causes and inspiring some new thoughts for me, and to anyone out there reading my thinking out loud. I'm no expert, but I think I have advanced my understanding of this through this exercise. Still interested in anyone else who has other theories or any success stories in reversing OSA so that you no longer need to use a CPAP machine. Thanks!
I have moderate OSA, have successfully used a CPAP machine nightly for 6 years, am 58, am not overweight (BMI 22), take no drugs - prescription or otherwise, and have no other health issues as measured by annual physicals, blood tests, etc.
Health research is so exciting these days, and much of what we're learning about the root causes of many of our conditions and diseases including aging, cancer, heart disease, dementia, stroke, diabetes, etc. relates to how our bodies evolved to survive over thousands of years vs. our lifestyles of the past couple of centuries and esp. the past few decades.
The high rate of OSA diagnoses in developed countries is highly correlated with obesity, which in turn makes sense from an evolutionary perspective of diet, exercise, etc. However, I've never been able to figure out why people like me are also getting diagnosed with OSA at a high rate. I'm curious if anyone can point to any theories or research that explain why this is happening from an evolutionary perspective.
I also wear a pulse oximeter at night and correlate pulse, O2, and movement with my CPAP data using the open-source OSCAR software. It's clear that without the CPAP machine, I have many O2 drops throughout the night that seem to be terrible, and with the CPAP machine, I have perfect O2 numbers all night long. But is that natural and necessary for someone with only mild or moderate OSA? It's different if you wake up feeling terrible and fall asleep during the day - CPAP is probably a huge health improvement for that. I also wonder if using a CPAP machine is addicting in the sense that my body is losing its ability to manage its oxygen during sleep on its own. Until we know more, I continue to use my CPAP machine nightly, but have also begun to successfully use an oral appliance when I travel, and will try the tongue exercise apps.
Brainstorming anything that might be behind this, although I don't find a lot evidence for any of them, certainly not a smoking gun:
Are we being over-diagnosed by an AHI threshold influenced by CPAP manufacturers? I read an article from Kaiser Health recently that implied this might be the case for mild OSA.
Are we using our tongue or throat muscles less than we did way back? A Swiss study I read about on this forum showed that didgeridoo playing significantly improved all sleep measures among OSA patients. A post here commented that singing isn't a part of our culture as much as it used to be. Did we have to chew harder before food was so processed and cooked so well, or before we started using knives to cut food into smaller pieces? If any of this is true, then some of the tongue exercise apps might be worth a try.
Are there toxins in our environment, such as our bedding or bedrooms that are causing this?
Is our sedentary lifestyle driving some other change neurologically or at a cellular level that affects oxygen processing?
Is there something about our modern diet and the resultant metabolic dysfunction that may be causing OSA, aside from obesity?
Is it possible that some level of hypoxia during sleep is normal and good for us? There's a school of thought that uses breathing exercises to induce hormesis, or mild stress, via hypoxia as a way to trigger our evolutionary survival mechanisms and create some metabolic flexibility. While too much is obviously bad, but are we over-diagnosing a lot of natural, mild cases?
Anyway, you get the idea I'm grasping here, but I feel like there's whole unknown set of discoveries out there about OSA, and that when we understand the evolutionary root causes better, we may find that we've over-diagnosed a whole lot of mild to moderate OSA patients and made their bodies less able to recover and adapt from some low level of hypoxia. Would love to read about any related studies and theories. Thanks!