Sleep apnea is linked to heart disease through its effect on blood pressure:
• Apnea patients with normal blood pressure run a risk of developing high blood pressure within four years. Hypertension is a major risk factor in the development of heart disease and stroke.
• Apnea patients have higher levels of sympathetic nervous system (SNS) activity during both wake and sleep than patients without sleep apnea.
• Involuntary functions such as heart rate and blood vessel constriction are controlled by the sympathetic nervous system.
• In persons without apnea, there is usually a decrease in SNS activity and blood pressure falls when sleeping. However, during apnea events, the higher level of SNS activity constricts the blood vessels, while the heart rate also jumps, slamming blood into tight vessels.
• Blood pressure spikes of up to 250/150 have been seen during apneas.
• Sleep apnea patients also have faster heart rates than non-apnea patients, even when awake, but have less variability in their heart rates. This combination of a less variable heart rate and greater variability in blood pressure is an indicator of potential cardiovascular problems.
Lastly, a condition known as central apnea may cause high blood pressure, surges of adrenaline, and irregular heartbeats. Central apnea occurs without snoring and is not caused by obstruction; rather it is caused by the failure of the brain to signal for a breath.