Dr. Rhonda Patrick: You mentioned sleep apnea, and that is another topic I wanted to discuss. I know many people who have had sleep apnea. How common is it, and what are some of the less obvious presentations that you see, especially in people who might not report feeling sleepy?

Dr. Michael Grandner: The first thing to know about sleep apnea is that it is shockingly common. The most recent data I have seen estimate that about one out of four or five men over 30 probably has at least some sleep-related breathing issues. If their BMI is over 30, it is more like 50 percent. Women get it less often, but it is also shockingly common in women. It might be closer to one out of every 15 or 20 women. As BMI goes up, it becomes more common.

It is so common that my threshold for screening is very low, especially among otherwise fit people. The normal risk factors can conceal it. As you gain weight, it becomes more likely because extra tissue can crowd the airway.

Dr. Rhonda Patrick: Muscle, too.

Dr. Michael Grandner: Muscle, too. Think of it this way: in most mammals, the airway is a straight line from the snout to the lungs. By moving upright, humans solved many problems and gained many benefits, but it created a problem because our airway now has a 90-degree angle. If you design a pipe and put a 90-degree kink in the hose, that bend is where problems will start. That is what happens around the throat, where the airway narrows. Any mass in the area, whether it is muscle, fat, tongue fat, or cheek tissue, can add to the narrowing. Even thinner people can have smaller airways that are more compressed. It is a vulnerability in human breathing physiology.

You can have four or five breathing pauses per hour during the night and still be in the normal range. Sleep apnea begins at five events per hour, the low end of mild, and it does not become moderate until 15 events per hour. Many people in the mild range do not have symptoms and might not be experiencing problems. We have a lot of flexibility in the system. But as you get older and neuromuscular control changes, and as more pressure is placed on the airway through weight gain or other factors, it becomes more common. My guess is that it has been common throughout history and was often attributed to something else, especially in people without obvious signs.

What are some less obvious signs? If a patient tells me, "I fall asleep fine, but I wake up in the middle of the night because stress wakes me, and then I have a hard time falling back asleep," I think there is a greater than 50 percent chance that it was a respiratory event. Stress does not wake you up. If you wake up and think you are stressed, your brain is reading physical signals such as an elevated heart rate, an elevated respiratory rate, and tense muscles. Because stress is readily available in the society we live in, we can fill that space quickly.

What was happening was not that stress woke you. Your breathing was becoming constrained. Your airway tried to open and was not successful, so it tried harder. In the worst case, you wake yourself up with a gasp because you can breathe normally when you are awake. It is a different neuromuscular control system. You get a sudden awakening because you received a small shot of adrenaline. If I gave you a little adrenaline during the night, you would wake up, have racing thoughts and physical signs of arousal, and struggle to fall back asleep. The stress was superimposed afterward.

When a patient says, "I wake up in the middle of the night because of stress or for no reason, and I cannot fall back asleep within a few minutes," something just happened. Some flare-up occurred somewhere.

Dr. Rhonda Patrick: You mentioned that deep sleep is important for clearing toxic waste, including protein aggregates such as amyloid-beta 42. Has anyone looked at people with Alzheimer's disease to see whether they have untreated sleep apnea?

Dr. Michael Grandner: Untreated sleep apnea is a known risk factor for neurodegeneration, especially when it is more severe. Mild to moderate sleep apnea is a gray area. Severe sleep apnea, 30 or more events per hour, seems reliably tied to poor outcomes. Mild sleep apnea seems tied to poor outcomes mainly when daytime symptoms are also present, such as fatigue and memory issues.

You can still get cell death and neuronal problems. Every time one of these respiratory events occurs, perhaps dozens of times per hour during the night, your oxygen level drops. It is not simply hypoxia that is the problem. It is intermittent hypoxia. Most people with sleep apnea do not have oxygen levels that remain very low for sustained periods unless they also have a lung condition such as emphysema. Instead, oxygen drops a few percentage points, the body wakes up, oxygen recovers, and then it drops again.

It is like constantly putting out small fires. None of the fires burns a house down, but they keep appearing everywhere. Cells release reactive oxygen species each time. The oxidative stress occurs, is quelled, and then returns throughout the night for days, months, years, or usually decades. The cells are trying to do their jobs while constantly dealing with this other stress. They do not get the recovery function they were built for, and the trajectory shifts slightly. That is why not only sleep deprivation, but also untreated sleep apnea, can lead to problems in the liver, kidneys, brain, heart, and immune system. Every cell that relies on oxygen starts to experience stress, and some cells are more sensitive than others.

Dr. Rhonda Patrick: Let us talk about treating sleep apnea. CPAP certainly works, although long-term adherence might not be very good. What are some of the best evidence-based non-CPAP interventions?

Dr. Michael Grandner: CPAP is a blunt instrument that works. Think of it as a splint that keeps the airway open. It creates a cushion of air, so if the airway wants to collapse, it cannot. CPAP means continuous positive airway pressure. It is continuous because it blows continuously. Positive pressure means blowing rather than sucking. It continuously blows air into the airway to keep it open. If the airway wants to close, enough air prevents it from closing.

Some people find it too uncomfortable, so there are other approaches. The one I use most often, especially for athletes who frequently present with mild to moderate sleep apnea, is a mandibular advancement device. It is essentially a retainer worn at night that pushes the jaw forward. It creates a little muscle tone while you rest. There is not enough muscle tone to keep you awake, but there is enough to keep this part of the airway more open than usual. For many people with milder sleep-related breathing issues, that is enough to eliminate enough events that they no longer notice the problem. You do not have to plug it in or replace a hose every few months. You do need to have it adjusted, and as your jaw remodels, you might need further adjustments.

There is a field called sleep dentistry, which is sleep medicine dentistry rather than sedation dentistry. Practitioners diagnose and treat sleep apnea with these dental devices. Another option is muscular myofunctional therapy. You can exercise these muscles so that they maintain more tone. That can work. There is famous research on people who play the didgeridoo, which requires cyclical breathing. It strengthens certain muscles so they retain more tone during sleep. That can help, especially in milder cases.

There is also a device called eXciteOSA. You place it on your tongue while you are awake, and it electrically stimulates the tongue muscle. It is similar to a TENS unit. The stimulation helps the tongue maintain more muscle tone when you go to bed, and it seems to work reasonably well.

Another device people may have seen advertised is Inspire, a name that means to breathe in. It is an implantable electrical device, somewhat like a pacemaker for the tongue muscle. Surgery is required. When it detects that the tongue is falling back, it stimulates the muscle to open the airway. It can work for appropriate candidates. There is no external equipment to replace, but surgery can have complications.

There are more options than ever, and the technology keeps improving. Even for CPAP, more than 200 types of masks are available. When someone dislikes a device because the mask is uncomfortable, it is rare that I find a mask problem that cannot be fixed.

Dr. Rhonda Patrick: What about mouth taping?

Dr. Michael Grandner: For decades, the sleep medicine field has used chin straps, which are elastic bands worn at night. They can be useful for people with mild snoring who do not have sleep apnea, people whose sleep apnea is mild, or people whose apnea comes from opening the mouth and allowing the tongue to fall back when they can breathe through the nose. Chin straps have worked well in these situations for decades.

I think mouth taping is a version of the same thing. It keeps the mouth closed while using special tape that still allows some airflow. If the problem is simply that you open your mouth, I have no problem with it, and it may help. But if you have sleep apnea and open your mouth to gasp because you cannot breathe, it is probably the opposite of what you want. If you need to open your mouth to breathe or your oxygen will plummet, do not tape it closed.

For milder snoring, or when you are using nasal strips or nasal splints to keep the nose open and only need to keep the mouth closed, I have no real problem with it. I do not think it will cure cancer and save the world. It gets overblown sometimes.

Dr. Rhonda Patrick: It has gotten overblown. It sounds more useful for snoring than anything else.

Dr. Michael Grandner: If keeping your mouth closed during the night solves your problem, go ahead. If you hope that keeping your mouth closed will solve your problem and it does not, there are other options.