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Sleep apnea results in periods of higher blood pressure (hypertension) because the heart tries to counter the build-up of carbon dioxide by pumping harder. Numerous studies have attempted to link sleep apnea to elevated blood pressure that occurs during waking hours. At this time, the link between sleep apnea and high blood pressure remains murky.

Early studies seemed to definitively link sleep apnea to high blood pressure. However, these studies frequently failed to take into account other risk factors for hypertension, most notably obesity, which occurs in almost half of sleep apnea cases. More recently, several large population studies have demonstrated a link between sleep apnea and elevated waking blood pressure. However, other studies that controlled for factors such as age, smoking, alcohol consumption and other risk factors have contradicted these findings.


While the association between these conditions and sleep apnea remains murky, researchers have uncovered a number of conclusive links that may one day help us better understand how sleep apnea affects cardiovascular health. For instance, sleep apnea is associated with increased risk of type 2 diabetes, independent of obesity. Similarly, apnea has been associated with lowered levels of HDL "good" cholesterol. Both of these are considered risk factors for coronary artery disease. Other studies have shown a correlation between sleep apnea and heart attacks at night and an increased risk of dying for people with sleep apnea. The specific causes associated with this link are unclear, but it is probably related to cardiovascular health.

Some studies have also linked sleep apnea to increased risk for transient ischemic attack and stroke. A study that accounted for overlapping risk factors found that people with untreated severe sleep apnea have three times greater risk of cardiovascular events, such as heart attack and stroke. Conversely, stroke patients may be at risk for sleep apnea some studies have shown. This risk may be linked to the fact that hospitalized stroke patients sleep on their backs, a position more conducive to sleep apnea. There is also a well-established link between sleep apnea and certain forms of abnormal heart rhythms. The most common rhythm disturbance connected to sleep apnea is a slow heartbeat (bradycardia). Sleep apnea has also been linked with increased risk of atrial fibrillation among patients who have already experienced atrial fibrillation.