There are two distinct types of sleep: rapid- eye-movement (REM) sleep (when most dreaming occurs), and non-REM sleep.
Typically, when you fall asleep you begin in non-REM sleep. Most people spend about 80% of the night in this type of sleep.
During non-REM sleep your heart rate, breathing, and blood pressure all drop to levels below those that occur while you are awake. During REM sleep-approximately 20% of your time asleep-both your blood pressure and heart rate can go up and down. Any time you wake up from sleep (even briefly), your heart rate and blood pressure climb, and your heart must work harder. When you wake up in the morning, your blood pressure and heart rate both go up and then stay at a higher level throughout the day.
Sleep And Heart Disease
Scientific studies have shown a direct connection among sleep, sleep disorders, and heart disease. There is an increased risk of sudden cardiac death (dying from heart stoppage) in the just several hours after waking up. It is known that there is an increased work demand on the heart that occurs when you wake up. People with sleep-related breathing disorders are more likely to have high blood pressure and are at a higher risk of heart disease and stroke. Treating certain sleep-related breathing disorders may actually decrease a person’s chances of developing certain heart diseases.
Hypertension (High Blood Pressure)
Several studies have shown a link between hypertension and an abnormal breathing pattern during sleep called obstructive sleep apnea (OSA). Hypertension is common in patients with OSA. There is also evidence that OSA can lead to the development of hypertension.
People with OSA have repeated interruptions in breathing during sleep. This is caused by collapse of the main breathing passage in the back of the throat. Every time this passage is blocked, breathing stops and oxygen is used up. After some time (usually 10-20 seconds, although up to one minute is not unusual) the breathing difficulty causes a brief awakening.
The awakenings are often so short that the person is unaware of any interruption in sleep. The awakening relieves the blockage in the breathing passage and normal breathing resumes. Unfortunately, when the person falls back asleep, the entire process can repeat (often hundreds of times per night). The drop in oxygen level from not breathing, and the increase in heart rate and blood pressure caused by waking up, causes stress for the heart. These nightly increases in blood pressure eventually lead to permanent increases in blood pressure, even during the day.
It is important to treat hypertension. Hypertension is a known risk factor for the development of other forms of cardiovascular disease such as heart attack, heart failure, and stroke. But treating hypertension may not be enough if the key reason for a person’s high blood pressure is an unrecognized sleep disorder like OSA.
Hypertension medications, for instance, may not work well in a patient with untreated OSA. Many people who have difficult cases of hypertension are later found to have untreated OSA. Treatment of OSA can improve hypertension. For this reason, it is important for your healthcare professional to investigate all of the possible causes of your hypertension, including sleep disorders like OSA.
Coronary Artery Disease
There is a direct association between sleep-related breathing disorders and cardiovascular disease. People with OSA, for example, have been shown to have higher rates of coronary artery disease (CAD). There are several reasons why this may occur: 1) OSA increases the risk for hypertension, which is a known cause of CAD; and 2) the events occurring during OSA can put excessive stress on the heart and turn mild CAD into serious CAD.
The flow of blood carries oxygen to the heart. In people with CAD the flow is limited due to narrowed arteries. If patients with CAD also have OSA, their blood oxygen levels drop and their heart rate and blood pressure rise, increasing the work required of their heart. As a result, the amount of oxygen supplied to their heart decreases just as their heart is demanding more oxygen. Several research studies have shown changes indicating a lack of blood flow on electrocardiogram during apneas in people with CAD.
Congestive Heart Failure
Congestive heart failure occurs when the heart is damaged and is unable to pump blood effectively. Disorders of sleep and breathing can cause heart failure or develop as a result of heart failure. Studies have shown that OSA is a significant risk factor for the development of congestive heart failure. In addition, people who have heart failure from another condition, such as CAD or hypertension, risk worsening their congestive heart failure if they develop OSA. The heart muscle, already in a weakened state, is unable to handle the additional stress caused by the OSA. However, treating OSA can improve heart function in patients with congestive heart failure.
About 40% of people with congestive heart failure also have a sleep-related breathing disorder called central sleep apnea (CSA). In CSA there are repetitive episodes of interruptions in breathing during sleep, just like in OSA. ‘The difference is that in CSA the breathing passage remains open but the person stops making efforts to breathe. Frequent awakenings and drops in the level of oxygen in the blood also occur in CSA. The awakenings increase heart rate and blood pressure, which can worsen heart failure.
Increased heart rate and blood pressure in turn leads to more CSA and causes a cycle that decreases heart function. ‘The first approach to treating CSA is to prevent it by treating the heart failure as thoroughly as possible. If CSA is still present, treatments are available to correct the CSA. Treatment of CSA can improve heart function as well as improve sleep quality.
Stroke
During a stroke the brain is damaged when the supply of blood and oxygen is reduced or cut off. Hypertension is the most common cause of stroke, and OSA can lead to the development of hypertension. In addition, OSA may cause strokes directly since the level of oxygen drops during apneas, Abnormal breathing patterns during sleep, especially OSA are also more common immediately following a stroke. Other effects of OSA such as excessive sleepiness from disrupted sleep and impaired thinking may hamper a person’s recovery from a stroke.
Arrhythmias
The heart normally beats with a regular rate and rhythm. Arrhythmia are irregular rhythms that may develop within a diseased heart. A common example is atrial fibrillation. Arrhythmias are more common in patients with OSA. This may be due to direct effects of OSA on the heart, or indirectly through associations with hypertension, coronary heart disease, and congestive heart failure. OSA treatment may help decrease arrhythmias.
Heart Conditions Associated With Sleep-related Breathing Disorders:
- Hypertension
- Coronary Artery Disease
- Congestive Heart Failure
- Stroke
Symptoms Of Obstructive Sleep Apnea
- Loud snoring
- Gasping or choking episodes while sleeping
- Witnessed episodes of stopped breathing while asleep
- Excessive sleepiness
- Falling asleep at inappropriate times
- Driving or workplace accidents
- Trouble concentrating, irritability, depression
- Morning headaches
Symptoms Of Central Sleep Apnea
- Symptoms of congestive heart failure (i.e. shortness of breath)
- Difficulty breathing while lying flat
- Restless sleep
- Waking up gasping or short of breath
- Witnessed episodes of stopped breathing while sleeping
- Unrefreshing sleep
- Snoring may be absent