Sleep apnea is a common sleep disorder where an individual’s breathing repeatedly stops and starts during sleep. These pauses can last for 10 seconds or longer and occur many times throughout the night. This condition significantly impacts the body’s cardiovascular system, particularly heart rate.
How Sleep Apnea Affects Heart Rate
During these breathing pauses, the body’s oxygen levels drop, and carbon dioxide levels can increase. This change in blood gas levels triggers a “fight or flight” response, activating the sympathetic nervous system. The brain, sensing a lack of oxygen, sends signals that cause blood vessels to tighten and the heart rate to quicken. This leads to sudden increases in heart rate, known as tachycardia, as the body compensates for reduced oxygen.
During the event, a paradoxical slowing of the heart rate, called bradycardia, can also occur, primarily due to vagal nerve stimulation. This slowing is brief, followed by a rapid acceleration once breathing resumes and the body reacts to oxygen deprivation. This constant fluctuation between slowed and accelerated heart rates throughout the night places considerable stress on the heart.
Repeated oxygen drops and sympathetic activation lead to heightened sympathetic drive, even during daytime. This sustained activation alters the nocturnal balance between the sympathetic and parasympathetic nervous systems. This results in magnified nocturnal blood pressure oscillations and increased short-term blood pressure variability.
Broader Cardiovascular Implications
The chronic stress from untreated sleep apnea can lead to several serious long-term cardiovascular complications. Repeated oxygen drops and surges in stress hormones contribute to chronic high blood pressure, known as hypertension. Hypertension is a major risk factor for various heart conditions and stroke.
Sleep apnea is also linked to irregular heart rhythms, or arrhythmias. Breathing disruptions can affect the heart’s electrical system, potentially leading to conditions like atrial fibrillation, a common irregular heartbeat. Individuals with sleep apnea are about four times more likely to develop atrial fibrillation. If left unmanaged, these arrhythmias can increase the risk of stroke and heart failure.
Decreased oxygen supply to the heart during apneic episodes can contribute to coronary artery disease, which involves the narrowing of blood vessels supplying the heart. Untreated sleep apnea also increases the risk of heart attack, stroke, and can lead to or worsen heart failure, where the heart becomes less efficient at pumping blood. The constant strain from repeated oxygen deprivation and sympathetic surges contributes to sustained cardiovascular damage.
Managing Sleep Apnea for Heart Health
Addressing sleep apnea is important for mitigating its cardiovascular risks. Diagnosis involves a sleep study, where breathing patterns, heart rate, blood oxygen levels, and other bodily functions are monitored overnight. This evaluation determines sleep apnea severity, categorized by the Apnea-Hypopnea Index (AHI) as mild (5-14 events per hour), moderate (15-29 events per hour), or severe (30 or more events per hour).
The primary treatment for moderate to severe obstructive sleep apnea is continuous positive airway pressure (CPAP) therapy. A CPAP machine delivers a gentle stream of air through a mask worn during sleep, keeping the airway open and preventing breathing pauses. CPAP therapy can stabilize heart rate, reduce blood pressure, and lower the risk of developing or worsening cardiovascular conditions.
For milder cases or for individuals who find CPAP challenging, lifestyle changes are recommended. These include weight loss, avoiding alcohol and sedatives before bedtime, and positional therapy to encourage sleeping on one’s side. Oral appliances, custom-made devices that reposition the jaw to keep the airway open, offer another treatment option. Effective management of sleep apnea is a proactive step toward protecting long-term heart health.