What can cause airway to collapse during sleeping?

I understand the obvious reasons, such as being overweight. Also, sleeping on your back can promote the tongue to slouch down and occlude the airway. Also, an anatomically small airway would be prone to self-obstruction. Additionally, I have even felt like a drying out of the mucousa (such as deep breathing in dry air) could inflame it and make it smaller. And so on…

What I am asking is, theoretically, what could cause a more than normal relaxation of the soft tissue in the upper airway? What type of pathology or predisposition could contribute to this, in theory?

Tranquilizers including benzodiazepines and morphine analogs.

Alcohol.

Some antidepressants, others can actually help, so no link on that mess.

Thanks, but I meant naturally occurring pathologies or predispositions.

Some people’s resting skeletal muscle tension is very soft while others is tense… could this predisposition include the tissue of the upper airway?

Ok, other then the usuals, the things that would cause airway closure not during sleep, but could also happen during sleep, say, emphysema etc.

But mainly, Sleep apnea. That doesn’t actually tell you what causes the closure other then what has already been said, but it did lead me to this.