Untreated Obstructive Sleep Apnea causes daytime sleepiness, worsening of hypertension, diabetes and cardio-vascular complications. Patients with Obstructive Sleep Apnea have an accident rate of seven times that of normal people. Sleep apnea is a potentially serious sleep disorder in which breathing repeatedly stops and starts. If you snore loudly and feel tired even after a full night's sleep, you might have sleep apnea.