This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cystic fibrosis & Sleep apnea, Subject name: Medicine
What is the most common cause of obstructive sleep apnea? 
Select and explain. 
A. Craniofacial abnormalities, B. Hypothyroidism, C. Alcoholism, D. Acromegaly
A: Craniofacial abnormalities
Answer: A: Craniofacial abnormalities 
Explanation: Craniofacial abnormalities are common in O.S.A in non-obese patients and children. Non structural risk factors for OSA include: Obesity, central fat distribution Male sex, middle age Alcohol use, sedative use, smoking Supine sleep position