Breathing irregularity, also known as apnea (5 letters), is a condition in which a person's breathing is interrupted during sleep. It can be caused by a variety of factors, including obesity, smoking, and alcohol consumption. Symptoms of apnea include snoring, daytime sleepiness, and difficulty concentrating. Treatment for apnea may include lifestyle changes, such as weight loss and quitting smoking, or the use of a continuous positive airway pressure (CPAP) machine.