OSA is a breathing disorder which blocks the airways and stops people breathing during sleep making them snore loudly, followed by feeling sleepy during the day. It is estimated that 4% of men and 2% of women in the UK have OSA. The British Lung Foundation is launching a national investigation to find out more about why so many people go undiagnosed as the consequences could be fatal with an estimated 20% of all accidents on motorways caused by sleepiness.