According to a 14-year study conducted by epidemiologists at the University of Wisconsin which evaluated 1522 healthy state workers averaging 50 years of age, as many as 365 (24%) were diagnosed with sleep apnea

http://www.totalhealthbreakthroughs.com/2009/02/dangers-of-sleep-apnea/

it can be up to 25% in men and up to 9% in women. The scary statistic is that this condition is not diagnosed in about 80-90% of people who have it, so instead, they are being treated for the end result which can be diabetes, depression, high blood pressure, etc. It is also known that significant sleep apnea happens in about 35% of chronic snorers. It’s also important to note that you don’t need to snore to have sleep apnea, as well.   

http://doctorstevenpark.com/sleep-apnea-basics/obstructive-sleep-apnea-a-primer

Obstructive Sleep Apnea (OSA) is the most common category of sleep-disordered breathing and affects approximately 38 million Americans (33% of the American adult population …. )

…. More than 800,000 patients are diagnosed with OSA per year in the USA alone.

http://www.imtheramedical.com/knowledge-center/index.php

nearly 100 million Americans wake up feeling as tired as when they went to bed, according to sleep research studies.

http://www.redrocknews.com/News/sleep-elusive-for-13-of-americans.html

Among the elderly, obstructive sleep apnea (OSA) is present in 24% of people who live independently, 33% of those in acute care institutions, and 42% who are in nursing homes.

http://www.betterlivinghomeimprovement.com/medicare-and-sleep-apnea-devices/