**5.1. Adult OSAS etiology**

General factors: Age, gender, obesity, alcohol consumption, sedative medicine consumption.

Anatomical factors: Lesions and anatomical variations, nasal obstruction, neck circumference, head and neck position, airway shape, and dimension.

Mechanical factors: Supine position, upper airway resistance, upper airway compliance, intraluminal pressure, extraluminal pressure, thoracic caudal traction, mucosal adhesive affects, vascular factors.

Neuromuscular factors: Upper airway dilator muscles, upper airway reflexes, dilator muscle, and diaphragm relations.

Central factors: Hypocapnic apneic threshold, periodical breathing, arousal, and cytokines.
