What causes obstructive sleep apnea?
Any condition that narrows the airway can cause OSA. ( eg ) Tonsill and adenoid enlargement includes obesity, hypothyroidism in adults. Some people have it in their genes. So sleep apnea can run in families.

Snoring and sleep Apnea:
Snoring may be the most common manifestation of the condition. The intensity of snoring increases as the airway narrowing increases. Usually in OSA, snoring can cause sleep disturbance to the bed partners, co-passengers when they travel in trains and at times the neighbours. But not all snorers have OSA. Some of them snore without compromising their airways and hence do not develop any problems.