Fainting (Syncope)

Fainting is a brief loss of consciousness caused by a temporary drop in blood flow to the brain.


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Circulatory system

Blood pressure

The Attorney General Passes Out

One minute, U.S. Attorney General Janet Reno was sitting in church. The next minute, she was peering up at a circle of concerned faces. Sixty-year-old Reno had just had a fainting spell, her second in less than a year. The September 1998 incident made the news because of Reno's famous name, but fainting is common. The cause of Reno's spell was unknown, but doctors said it might have been due to her heavy work load or the tremendous job stress that comes with being the chief law officer of the United States.

Blacking Out in Blue Skies

In World War II, fighter pilots sometimes lost their lives because of fainting.

During high-speed flight, very rapid changes in speed create a force that is expressed as a unit of gravity (g). A force of 4 to 6 g makes blood become very heavy and pool in the lower part of the body, robbing the brain of its blood supply. Many high-speed moves create a force this great. For example, pulling out of a dive can produce a force up to 9 g. When this happened, pilots fainted and crashed.

It was up to scientist Wilbur R. Franks to find a solution to this problem. In 1942, Franks invented the first anti-gravity suit. This is a flight suit with special pants that apply pressure to the legs and belly, forcing blood back into the upper part of the body. Franks's invention gave Allied pilots a competitive edge during the war. The suits worn by jet pilots and astronauts today are still based on his design.

What Is Fainting?

Fainting, also known as syncope (SING-ko-pee), is a brief loss of consciousness caused by a temporary drop in blood flow to the brain. Blood carries oxygen to the brain. Without enough oxygen, brain processes slow down, and the person may pass out briefly. There can be several reasons for the sudden drop in blood flow, including an irregular heart rate or rhythm, a dip in blood pressure, or the pooling of blood in the legs usually after a prolonged period of standing. Although fainting can be scary and embarrassing, it usually is not a cause for panic. Healthy people sometimes faint when they are extremely tired, get bad news, or see something upsetting. In other cases, however, fainting may be a sign of a more serious medical condition.

What Causes Fainting?

One in three people faints at some point in life. The problem occurs in people of all ages, although it is most common in people over age 65. There are many possible causes. These are some of the more frequent ones:

Heart disorders

The most serious causes of fainting usually involve the heart or blood vessels. In some cases, the heart beats too fast or with an irregular rhythm, reducing the amount of blood it pumps. In other cases, there is a narrowing of the valve that lets blood out of the heart or a partial blockage of the blood vessels that carry blood to the head, limiting blood flow to the brain.

Emotional stress

Stress, fright, or sudden pain can arouse the nervous system, which, in turn, can signal the heart to slow down or the blood vessels to widen. If such changes happen too quickly, a person's blood pressure can drop suddenly. This reduces blood flow to the brain, and the person may faint.

Dancing Mania
and Mass Fainting

The phenomenon of mass fainting was reported to have occurred in the Middle Ages as a result of what was known as dancing mania.

Dancing mania reportedly was induced by minstrels who played intoxicating music at medieval festivals. The music stimulated fits of wild dancing, leaping, hopping, and clapping that led to hyperventilation, heart palpitations, and other symptoms.

Dancing mania curiously parallels the fainting that sometimes occurs at present day rock concerts.

Heavy sweating

Sweat contains sodium, a mineral that plays a key role in blood pressure control. Heavy sweating is another possible cause of a sudden dip in blood pressure. This often is a problem for people who take part in strenuous physical activities under hot, humid conditions.

Standing up quickly

When most people stand up, the nervous system triggers a reflex response that increases the heart rate and blood pressure. This insures that enough blood gets to the brain. In some people, particularly the elderly, these responses may not occur fast enough. Blood may pool in the legs. When too little blood reaches the brain, the person may faint.

What Happens When People Faint?


Some people simply lose consciousness and slump down without warning. However, many people feel dizzy, lightheaded, or sick to their stomach just before they faint. They may become sweaty and pale, and they may have a graying out of vision. By definition, a faint does not last long. Falling down places the head at the same level as the heart. This helps restore blood flow to the brain. The person soon regains consciousness, usually within a minute or so.


A person feeling faint should lie down immediately and not try to stand or walk. If the person who faints dos not regain consciousness within a minute or two, it is important to get emergency medical help immediately. While awaiting emergency help, adult bystanders probably will elevate the legs of the person who has fainted; loosen belts, collars, or tight clothing; and check that the person's airway remains open, as people who faint may vomit as well. They will not move the person who has fainted until medical help arrives because a fall may have injured the person.

The person who has fainted probably will regain consciousness quickly, but may continue to feel a bit weak for a little while. To keep from fainting again, the person should stay lying quietly for a few minutes.

Even when people recover promptly, they should contact their doctors about a first fainting attack, about repeated fainting spells, or about other possible symptoms including irregular heartbeat, chest pain, shortness of breath, blurred vision, confusion, or trouble talking.

See also
Altitude Sickness
Heart Disease
Stress-Related Illness


American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231, (800) AHA-USAI. This group has information about syncope on its website.

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