How Sleep Apnea Affects Blood Pressure

High blood pressure, also called hypertension, is a common health issue in which the amount of force that pumps blood through blood vessels is higher than normal. People with hypertension often don’t have symptoms1 but learn they have high blood pressure during routine checks at a doctor’s office. If left untreated, high blood pressure puts a daily strain on the cardiovascular system which may lead to stroke, heart disease, and other conditions. Fortunately, managing hypertension with medication and lifestyle changes can reduce your risk for harmful health effects.

Sleep apnea is a sleep disorder that causes numerous lapses in breathing2 during sleep. There are two types of sleep apnea: obstructive sleep apnea (OSA) and central sleep apnea (CSA). OSA is marked by episodes of airway collapse, which blocks airflow into the lungs and often causes snoring and gasping during sleep. In CSA, breathing lapses occur because of a lack of communication between the brain and the muscles involved in breathing.

It’s important to understand the relationship between hypertension and sleep apnea because these two conditions affect one another, and treatment for sleep apnea can lower blood pressure in people who have both.
 

What Is the Relationship Between Sleep Apnea and Blood Pressure?

Of the two types of sleep apnea, only OSA is linked to high blood pressure3. CSA isn’t a known cause of hypertension, but it develops in 30 to 50% of people with heart failure.
The prevalence of OSA4 is estimated to be between 4 and 7% of the general population, but it affects 30 to 40% of people with hypertension. Of people diagnosed with OSA, it is estimated that around half also have high blood pressure.

In healthy individuals, blood pressure naturally lowers by between 10 and 20%  at night, a phenomenon that is sometimes referred to as “blood pressure dipping5“. People with severe OSA experience blood pressure dips of less than 10%, which indicates a “nondipping” blood pressure pattern.

People who have nondipping blood pressure at night face an increased risk for cardiovascular issues6. Additionally, many patients with OSA experience a sudden and pronounced elevation of their blood pressure when they wake up in the morning. This “morning surge” is another factor that may increase risk7 for cardiovascular disease. Moderate to severe OSA increases all-cause and cardiovascular mortality.

OSA doesn’t only affect blood pressure at night. Studies show that daytime blood pressure levels also increase with sleep apnea severity.
 

How Does Sleep Apnea Cause High Blood Pressure?

Sleep deprivation strains the heart, and OSA in particular causes an over-activation of the sympathetic nervous system8, which may lead to high blood pressure. The role of our sympathetic nervous system is to control our “fight or flight” response9. When activated, the sympathetic nervous system triggers a series of temporary physical reactions, including faster heart rate, higher blood pressure, dilated pupils, and increased metabolism. All of these changes help us respond to stressful events; however, excessive activation of the sympathetic nervous system can lead to chronically elevated blood pressure.Each time a person with OSA experiences airway collapse and briefly stops breathing during sleep, their sympathetic nervous system becomes activated and blood pressure rapidly spikes10 when they resume breathing. Sometimes, this sequence of pausing and resuming breathing can cause a person to wake from sleep. When a person wakes up after an OSA event, activation of the sympathetic nervous system and blood pressure levels escalate to an even greater degree.

Additionally, when sleep is disrupted by OSA symptoms, the body releases sympathetic nervous system hormones called catecholamines11 into the blood. Catecholamines are stress hormones that are majorly released by the adrenal glands. Examples of catecholamines include dopamine and epinephrine (also called adrenaline). High levels of catecholamines in the blood cause high blood pressure.
 

Obesity and Insulin Resistance

OSA, hypertension, obesity, and insulin resistance share a complex relationship in which all four factors influence and exacerbate one another.
Obesity12 predisposes people to OSA. Obesity also increases a person’s risk of developing high blood pressure. Research suggests that when a person has both OSA and excess weight, the two conditions may affect one another in ways that impair cardiovascular health. For example, OSA and obesity both cause elevated levels of leptin13 in the blood. Leptin is a hormone that promotes hunger, which can further contribute to weight gain. Leptin also stresses the cardiovascular system and may promote the development of hypertension.

People with insulin resistance14 require higher and higher levels of the hormone insulin to be able to use a type of sugar in the blood called glucose for energy. Over time, insulin resistance can result in uncontrolled glucose levels in the blood and the development of diabetes. Obesity is a known cause of insulin resistance. Recent studies have shown that OSA is also a cause of insulin resistance, regardless of one’s weight. High blood pressure is yet another risk factor for insulin resistance. Because insulin resistance is an activator of the sympathetic nervous system, it may cause or worsen high blood pressure as well.
 

How Does Sleep Apnea Treatment Affect Blood Pressure?

There are a number of treatment options for OSA. Treatment not only improves sleep quality but could also help manage hypertension. The most common and effective treatment is called continuous positive airway pressure (CPAP).

CPAP treatment involves wearing a facemask attached to a machine that pumps air into the lungs at night. It works by preventing the airway from collapsing, which improves sleep quality in people affected by OSA. Studies investigating the effects of CPAP in patients with hypertension and OSA have shown that treatment with CPAP lowers blood pressure during the day and at night, especially in patients with severe OSA. CPAP also reduces catecholamine15 levels.

Some patients have a hard time adjusting to the CPAP facemask at night. Consistent, proper use of CPAP is important in order to effectively manage OSA and hypertension. Mouthpieces are one alternative to CPAP and are designed to help maintain an open airway during sleep. Research is needed to determine if mouthpieces also lower blood pressure in people who experience high blood pressure and OSA. Certain surgical procedures are also done to treat OSA in selected patients.
Losing weight either through diet and lifestyle changes or through weight-loss surgery is another approach to managing OSA that may also lower blood pressure16.
 

Should I Talk To My Doctor About Sleep Apnea?

If you have high blood pressure and are concerned about whether you might also have sleep apnea, speak with a doctor. Diagnosis is the first step to accessing effective treatments for OSA that may improve your sleep and blood pressure. Consider whether any of the following symptoms17 apply to you:

• Daytime sleepiness
• Difficulty with attention and memory
• Headaches in the morning
• Dry mouth when waking up
• Irritability, anxiety, or depression

Sleep apnea is often not recognized by the affected individual. In many cases, a bed partner notices nighttime symptoms of OSA, which prompts a visit to the doctor. If you share a bedroom or home with someone else, ask if they have noticed you exhibiting any of these signs while you are sleeping:

• Loud snoring
• Choking or gasping during sleep
• Pauses in breathing during sleep

Experiencing one or more of these symptoms does not necessarily mean you have sleep apnea, but it is a good reason to bring up sleep with your doctor.