Fainting (Syncope)

Key Points

• Fainting is a brief loss of consciousness.

• Fainting may be more common in people with Down syndrome.

• Fainting may be more common because of differences in body function in people with Down syndrome and/or several health conditions that are more common in people with Down syndrome. 

• If no concerning medical or psychological conditions are found, there are some measures that can be done at home to reduce fainting.

 

What is fainting?

Fainting is a loss of consciousness (or becoming unconscious). Unconscious people are not aware of people or activity around them and are unable to respond to people or activities. Fainting is caused by a drop in blood flow to the brain. It can also be caused by a decrease in oxygen or glucose (sugar) in the brain or a slowing of brain activity from other causes. Often fainting lasts a relatively short time (less than a couple minutes) with a quick recovery. However, if the cause of the fainting persists, it may last longer.

Other terms used to describe these events are “passing out,” “loss of consciousness,” or “blackout.” The medical term for fainting is syncope. 

The autonomic nervous system plays a big role in fainting. The autonomic nervous system is the part of the nervous system that functions without requiring conscious thought (it functions automatically). It helps with maintaining blood pressure and pulse (and many other functions).

Many other organs and body systems may also be involved in fainting including the brain and other parts of the nervous system, the heart and blood vessels, and other body systems that may trigger the autonomic nervous system.

 

Why is this important in people with Down syndrome?

As noted above, the function of the autonomic nervous system often is involved in fainting. The autonomic nervous system works differently in people with Down syndrome. People with Down syndrome typically have lower blood pressures and pulses than those without Down syndrome. Since the pulse and blood pressure of individuals with Down syndrome are starting at lower levels than those without Down syndrome, any further reduction in blood pressure or pulse may more easily/quickly get to a level that causes fainting.

The response of the autonomic nervous system to stimuli such as pain or fear also appears to be exaggerated or heightened in some individuals with Down syndrome. When the stimulus occurs, a person with Down syndrome may have an increased response with more decline in blood pressure and pulse (heart rate) which can cause fainting. 

In addition, in response to lower blood pressure in the brain, the body normally compensates in a variety of ways (e.g., increases heart rate and increases the amount of blood the heart pumps with each heartbeat) to maintain or return to the normal blood pressure in the brain. This response appears blunted or decreased in some people with Down syndrome.

 

What causes fainting?

There are many possible causes for fainting. Some of the causes include: 

Vasovagal syncope

Vasovagal syncope is fainting related to the triggering of the vagus nerve, the nerve that transmits many of the signals in the autonomic nervous system that are involved in blood pressure and pulse. The vagus nerve can be triggered by an abnormal or exaggerated response to various stimuli such as anxiety, pain, fear, straining to have a bowel movement or urinate, coughing, seeing blood, and other stimuli.

When the vagus nerve is triggered, it causes low heart rate (bradycardia) and dilation of peripheral blood vessels, which then causes a short episode of low blood pressure (hypotension) which results in fainting. Vasovagal syncope is also known as neurocardiogenic syncope because both the nervous system and the heart/vascular system are involved.

Pain

Many people with Down syndrome do not complain of pain or complain of pain less than others. Individuals with Down syndrome experience pain but often do not report it. Therefore, it is important to watch for other signs of pain such as facial grimacing or changes in behavior. For some individuals, the pain will be significant enough to trigger the autonomic nervous system and cause fainting. 

Gastrointestinal issues

Gastrointestinal issues can be a common source of pain or discomfort for individuals with Down syndrome. Constipation and celiac disease are both more common in people with Down syndrome and can be associated with gastrointestinal discomfort, which can contribute to fainting.

Heart conditions

Fainting can be associated with several heart conditions including: 

Structural abnormalities of the heart

These may include abnormal holes within the heart, damaged or abnormal heart valves, or damage to the wall of the heart. If these abnormalities prevent the heart from pumping adequate amounts of blood to the brain, fainting may occur. These abnormalities may progress gradually and lead to fainting or there may be a more acute situation where additional damage occurs and causes fainting. Sometimes something will stress the damaged heart beyond its capabilities. Examples of this include an infection elsewhere in the body that causes the heart to need to beat harder, but the weakened heart is not capable of that increased work and stops pumping well.

About 50% of infants with Down syndrome are born with a heart defect (congenital heart disease) and they are more at risk to develop abnormal heart function in adulthood. Even if it is corrected appropriately in infancy or childhood, those individuals are more at risk to develop further abnormalities of the structure of the heart and/or abnormal heart rhythms. Due to that reason, the Global Medical Care Guidelines for Adults with Down Syndrome recommend regular follow up throughout life for those with history of congenital heart disease. Individuals who did not have congenital heart disease are not free of risk of heart problems in adulthood but are less at risk than those with a history of congenital heart disease.

Myocardial infarction or heart attack

A myocardial infarction or heart attack occurs when decreased blood flow to the heart muscle results in damage to the heart muscle. This can result in decreased blood flow to the brain and fainting.

Fortunately, heart attacks are less common  in people with Down syndrome so that is less likely to be the cause in someone with Down syndrome.

Rhythm disturbances

If the electrical function of the heart is not starting correctly or if those electrical signals are not transmitted to other parts of the heart correctly, the heart may pump inadequately, and the person may faint.  

Moyamoya disease

Moyamoya disease is a rare disease for which symptoms usually start in childhood but can also occur in adults. It occurs when arteries in an area called the basal ganglia at the base of the brain become blocked. It can cause fainting. Moyamoya disease can also cause a variety of other symptoms, including those associated with having a stroke. More information about moyamoya can be found on the National Institute of Neurological Disorders and Stroke website .

While moyamoya is more common in people with Down syndrome than people without Down syndrome, it is still uncommon in people with Down syndrome. Our study  identified 14 cases among 6,078 individuals with Down syndrome (0.23%).

Medications

Some medications can reduce heart rate and/or blood pressure or have a direct effect on the brain (e.g., sedation side effects of diazepam (Valium) or lorazepam (Ativan)) and cause fainting. 

Orthostatic or postural hypotension

Orthostatic or postural hypotension (low blood pressure) is a sudden drop in blood pressure that is caused by a change in position such as when a person stands up from a sitting or lying position. There are many causes for this which are listed below. If the cause is severe enough, the fainting sometimes occurs when the person is already standing (they are not changing position) or even while the person is still lying down.

Dehydration

Dehydration can be due to inadequate intake of fluids or loss of fluids (e.g., vomiting, diarrhea, sweating). The fluid in the blood stream decreases causing reduced blood flow to the brain.

In our experience, many people with Down syndrome do not drink enough fluids. There can be an additive effect with different causes of fainting. For example, even if the person is only mildly dehydrated, the difference in the function of the autonomic nervous system may make the effect of the dehydration more noticeable. The body of a person with Down syndrome may not be able to compensate for the dehydration like it might in someone without Down syndrome.

Anemia

Anemia is a decrease in the red blood cells in the bloodstream which can reduce the blood’s ability to carry oxygen. With decreased oxygen in the blood being delivered to the brain (and the rest of the body), the person may faint.

Iron deficiency and vitamin B12 deficiency can cause anemia. Both deficiencies can be caused by celiac disease, which is more common in people with Down syndrome. These deficiencies can be present due to other causes, too.

Anemia can also be caused by ulcers in the stomach. In some individuals with Down syndrome, due to differences in pain perception and/or pain reporting, they may not report the pain of an ulcer but instead the first symptom may be fainting due to severe anemia. 

Overheating

When a person gets hot, the blood vessels in the skin dilate to release body heat. If the person gets overheated, the blood vessels may dilate to such a great degree that a reduction in blood pressure occurs. If the blood pressure goes too low, the person may faint.

Many people with Down syndrome do not sweat as much as people without Down syndrome and/or have greater difficulty regulating body temperature. When they get overheated, they may faint.

Standing too long in one position

With prolonged standing, blood pools in the legs due to the pull of gravity and not enough blood flows back to the heart to pump to the brain. Dehydration may also contribute if the person is standing in hot conditions, or they are not drinking enough fluids. In addition, with prolonged standing the vagus nerve may become overstimulated causing lower heart rate and even further lower blood pressure.

Carotid sinus syndrome

Some individuals have increased sensitivity when their carotid sinus is massaged. The carotid sinus is in the neck, and it helps monitor blood pressure changes. When it is massaged or rubbed, the blood pressure and pulse tend to decrease. In some individuals it is very sensitive, and they may faint due to much lower blood pressure and pulse. Some individuals are so sensitive that wearing a shirt collar that is too tight can cause enough pressure on the carotid sinus to cause fainting.

Hypothyroidism

The thyroid is a gland in the neck that produces thyroid hormone. When the thyroid gland is underactive, the heart rate decreases. If the heart rate goes low enough, fainting can occur. Hypothyroidism is more common in people with Down syndrome.

Hypoxia

Hypoxia is low oxygen in the blood that can occur for many reasons including pneumonia, injury to the lungs, sleep apnea, blood clots in the lungs (pulmonary embolism), and smoking.

Hypoglycemia

Hypoglycemia is low blood glucose (sugar) that can occur for many reasons. The main energy source for the brain is glucose. If the brain does not get enough glucose, fainting can occur. For example, people with diabetes mellitus may have a reaction to their medication that causes low blood sugar and then fainting. There are a variety of reasons a person with Down syndrome may develop a low blood sugar. 

Hyperventilation

Hyperventilation  is breathing too fast, often due to anxiety. It can cause the lungs to release too much carbon dioxide. Low carbon dioxide causes the blood vessels in the brain to narrow (constrict) causing decreased blood flow to the brain which can cause fainting.

Sepsis

Severe infections can cause sepsis which can cause blood vessels to dilate and blood pressure to drop which can result in fainting. People with Down syndrome are at greater risk for serious infections, in part because of a reduced ability of the immune system to fight infections. 

Transient ischemic attacks (TIA) or strokes

Transient ischemic attacks (TIA) or strokes are caused by low blood flow to the brain due to blockages in the blood vessels in the brain. Blockages can cause a temporary decrease in blood flow to the brain (TIA) or a stroke that causes permanent brain damage. Depending on where in the brain the injury occurs, fainting can be one of the symptoms. Research  has found that individuals with Down syndrome who were born with heart disease (congenital heart disease) are more likely to have a stroke in adulthood.

Psychiatric conditions

Some individuals with psychiatric disease can have fainting secondary to the psychiatric disease rather than one of the physical causes noted above. These may include:

• Somatization, physical symptoms that have a primary psychological basis. Individuals may faint even though there is no apparent physical cause for the fainting.

• Hysteria, a condition of extreme emotion or excitement.

• Vasovagal syncope (see above) due to psychological conditions such as panic or fright. 

Seizure disorders

Seizures themselves are not a cause of fainting. However, in some situations, a seizure can cause a drop in blood pressure that can cause fainting as a secondary effect. Seizures are more common  in people with Down syndrome. 

Other causes

The above is a partial list and there are other causes of fainting not listed here. 

Unknown reasons

Sometimes, there is not a clear cause for an episode of fainting. In elderly people without Down syndrome, research  has shown that, even with a thorough evaluation, a clear cause for an episode of fainting may not be found in about one of three people presenting with fainting.

 

What other symptoms may occur?

In addition to fainting, the person may get sweaty, develop an upset stomach and/or feel like they will vomit, feel lightheaded before they faint, feel weak and/or have other symptoms noted in this article from the Cleveland Clinic .

 

Diagnosis

After a fainting episode, an individual should be assessed by a health care professional. The American College of Emergency Physicians  recommends calling 911 or your local emergency number. Depending on the type of episode, the emergency personnel will determine if the individual needs to be taken to an emergency facility and assessed immediately.

An assessment for fainting may include: 

Blood testing

Blood tests can help assess for a variety of conditions that can cause fainting. While some additional tests may be indicated based on the history and physical, some tests that can assess for common conditions in people with Down syndrome include: 

• Complete blood count (CBC)

• Chemistry panel (complete metabolic panel/CMP)

• Thyroid testing (TSH, T4)

Heart evaluation

A heart evaluation is important for people who faint, especially those with a history of congenital heart disease. The evaluation may include an electrocardiogram (EKG), an echocardiogram, and an assessment by a cardiologist. An event monitor or Holter monitor may also be indicated. These devices monitor the electrical activity of the heart continuously for a designated amount of time such as 24 or 48 hours or one week (sometimes longer).

The sinoatrial node, the natural heart pacemaker, can become dysfunctional and cause the heart to not beat appropriately. Usually, the heart will beat too slowly to adequately pump blood to the brain and the rest of the body. This may require the placement of a pacemaker to prevent recurrent fainting.

Brain evaluation

An evaluation for seizures may include imaging of the brain (CT scan or MRI) and/or electroencephalogram (EEG). An assessment for moyamoya disease may include a CT scan, MRI, or other forms of brain imaging.

Tilt table test

Usually in consult with a cardiologist, a tilt table test can be done. This test assesses the effect of change in position on blood pressure and heart rate. Someone with autonomic nervous dysfunction can have an abnormal response to a tilt table test. 

This is a partial list of possible next steps. A health care professional may recommend additional assessment be done as indicated by the history, physical exam, and initial testing. 

 

Treatment

When a specific cause of fainting is found, the treatment can focus on addressing that cause. This article won't address treatment for each possible cause for fainting but there are some specific treatments to consider in people with Down syndrome: 

Pain

Address possible causes of pain including gastrointestinal (GI) pain. Assess for and treat celiac disease, constipation, heart burn (gastroesophageal reflux disease), and other GI conditions if diagnosed. This will not reduce the autonomic nervous system sensitivity but can reduce the discomfort that can trigger the autonomic nervous system. 

Blood pressure

Since the blood pressure of people with Down syndrome tends to be lower all the time, it is sometimes necessary to add a medication that increases blood pressure if they are recurrently fainting. A couple examples of these medications are midodrine and fludrocortisone.

Pacemaker

Placement of a heart pacemaker may be necessary for some individuals. A battery-operated device is surgically placed under the skin, usually in the upper chest. A wire from the pacemaker is attached to the heart and the pacemaker directs the heart to beat slower than a set number of heart beats per minute. The battery lasts several years before it must be replaced. The pacemaker is checked regularly to ensure that it is still working correctly, and many of these visits can be done at home with transmission of the pacemaker function via a phone.

 

What can be done at home?

• Increase blood pressure with liquids and salt. Encourage greater fluid and salt intake. Some individuals benefit from putting a glass of water and saltine crackers or pretzels next to their bed and eating the salty food before getting out of bed. Since high blood pressure (hypertension) is less common in people with Down syndrome, there is usually less need for careful salt restriction. Careful salt restriction can contribute to fainting in some individuals with Down syndrome.

• Compression stockings may help to promote the return of blood from the legs back to the heart and prevent pooling of blood in the legs.

• Using the muscles of the legs by moving the feet and legs can promote blood flow back to the heart from the legs.

• If dizziness or fainting is occurring when getting up from lying or sitting, get up more slowly, sit or stand for a moment before starting to walk.

• If low blood sugar is contributing to fainting, there are several measures that can be done at home to reduce the likelihood of this occurring, as described in this Hypoglycemia article.

 

Resources

Down syndrome

Celiac Disease

Compression Socks for People with Down Syndrome

Global Medical Care Guidelines for Adults with Down Syndrome

Hypertension and Hypotension (High and Low Blood Pressure)

Hypoglycemia (Low Blood Sugar)

Hypothyroidism and Hyperthyroidism

Iron Deficiency and Down Syndrome

Pain in People with Down Syndrome

Pneumonia in People with Down Syndrome

Temperature Regulation in People with Down Syndrome

Tips for Staying Hydrated

Vitamin B12 Deficiency

 

General

Fainting

Hyperventilation

Moyamoya Disease

Vasovagal Syncope

 

References

Altuna M, Giménez S, Fortea J. Epilepsy in Down syndrome: A highly prevalent comorbidity. J Clin Med. 2021;10(13):2776. doi:10.3390/jcm10132776

Chen-Scarabelli C, Scarabelli TM. Neurocardiogenic syncope. BMJ. 2004;329(7461):336-341. doi:10.1136/bmj.329.7461.336

Chicoine B, Rivelli A, Fitzpatrick V, Chicoine L, Jia G, Rzhetsky A. Prevalence of common disease conditions in a large cohort of individuals with Down syndrome in the United States. J Patient Cent Res Rev. 2021;8(2):86-97. doi:10.17294/2330-0698.1824

de Ruiter SC, Wold JFH, Germans T, Ruiter JH, Jansen RWMM. Multiple causes of syncope in the elderly: diagnostic outcomes of a Dutch multidisciplinary syncope pathway. Europace. 2018;20(5):867-872. doi:10.1093/europace/eux099

Dimopoulos K, Constantine A, Clift P, et al. Cardiovascular complications of Down syndrome: Scoping review and expert consensus. Circulation. 2023;147(5):425-441. doi:10.1161/CIRCULATIONAHA.122.059706

Fitzpatrick V, Rivelli A, Bria K, Chicoine B. Heart disease in adults with Down syndrome between 1996 and 2016. J Am Board Fam Med. 2020;33(6):923-931. doi:10.3122/jabfm.2020.06.190425

Hilgenkamp TIM, Wee SO, Schroeder EC, Baynard T, Fernhall B. Peripheral blood flow regulation in response to sympathetic stimulation in individuals with Down syndrome. Artery Res. 2018;24:16-21. doi:10.1016/j.artres.2018.10.001

Kennedy J, Devlin P, Wilson CM, McGlinchey PG. Sinoatrial node disease in adults with Down's syndrome. Ulster Med J. 2018;87(1):37-38.

Sinton JW, Cooper DS, Wiley S. Down syndrome and the autonomic nervous system, an educational review for the anesthesiologist. Paediatr Anaesth. 2022;32(5):609-616. doi:10.1111/pan.14416