There are a number of factors that can predispose you to not breathe well at night. We will go over just a few of these factors that relate to your anatomy. In general, the more the tissues of the neck and mouth collapse the more likely air will be impeded, thus causing snoring or sleep apnea.
1. The more elastic your tissues the more collapsible your airway
As we age our tissues become more elastic and malleable. This decrease in elasticity can cause the airway to collapse easier. In people with sleep apnea it has been found that their airways are more likely to collapse with less internal pressure. As we breathe, this creates pressure inside our body causing an influx of air into the lungs. If this pressure is too much for the walls of the airway, they start to collapse and cause an obstruction for the incoming air.
2. The longer the pharynx the more collapsible your airway
There are many reasons why people think that men are more likely to have sleep apnea. One reason is that they typically have longer pharynx. The pharynx is the portion of the airway from the nose to the mouth. The longer the structure the more flexible it will be. In addition, a longer pharynx means more surface area along the airway. This will cause a higher amount of total airway pressure. This additional pressure will exert forces to collapse the airway.
3. The less muscle in the tongue and palate the more collapsible your airway
People with sleep apnea have been found to have smaller muscle fiber diameter in the tongue and soft palate. Muscles are groups of arranged fibers running in a particular direction. When looking at the tongue for instance, there is a lot of different types of tissue making up structure. The tongue will have fat, collagen, muscle, and other different types of tissue. The less muscle and more fat/collagen in the neck area the more the airway is likely to collapse.
4. The less your lungs can fill up the more collapsible your airway
Each person's lungs will fill up to a different volume when breathing. Many factors can reduce lung volume. Some factors include increased fat content causing not enough room for the lungs or lung damage such as that caused by smoking. If the lungs cannot fill up as much this causes the airway to collapse more.
5. Positioning your jaw/head/neck differently can change the collapsible of your airway
When lying on your back, gravity will cause the tongue to fall backwards into the airway. When children lie on their stomach and twist their neck this can also cause the airway to collapse more. In addition, when the jaw is open and not stabilized this can narrow the airway.
Photo credit from: J Appl Physiol (1985). 2014 Feb 1;116(3):314-24. doi: 10.1152/japplphysiol.00539.2013. Epub 2013 Jul 3. Accessed online: https://www.physiology.org/doi/pdf/10.1152/japplphysiol.00539.2013