Even mild sleep apnea increases heart risk.  Research shows that minimally symptomatic obstructive sleep apnea can increase arterial stiffness.
D002318:Cardiovascular Diseases / Q000209:etiology*; D006801:Humans; D012307:Risk Factors; D012891:Sleep Apnea Syndromes / Q000150:complications* / Q000503:physiopathology / Q000628:therapy