Fainting is a sudden, temporary loss of consciousness that usually results in a fall. Healthcare professionals often use the term ‘syncope’ when referring to fainting because it distinguishes fainting from other causes of temporary unconsciousness, such as seizures (fits) or concussion.
Why fainting happens
In order to function properly, the brain relies on oxygen that is carried in the blood. Fainting can occur when the blood flow to the brain is reduced. This is usually brief and quickly corrected by the body, but it can cause people to feel odd, sweaty and dizzy. If it lasts long enough, they may fall down. This is called a faint.
The cause of the reduced blood supply to the brain can vary, but it is sometimes caused by blood pooling in the big veins in the legs. When someone stands up, it is more difficult to get blood back to the heart, which means there is less blood to pump to the brain. Most people faint from standing, although occasionally fainting can occur from sitting.
When someone falls down, the blood flows more easily from the legs back to the heart and then on to the brain. As their brain receives more blood, they recover from the faint.
Other factors that can make fainting more likely include:
- reduced blood volume, for example, if someone has not drunk enough water
- anything that slows the heart down, for example, being sick
See Fainting - causes for more information.
How common is fainting?
Fainting is very common. About 1 young child in 100 may faint, for example, as a result of a fear or pain. One study found that, by 40 years of age, 95 out of 100 people had fainted at least once.
Studies across Europe suggest that about 1 visit in 100 to the emergency departments of hospitals are due to fainting.
In 2008 to 2009, nearly 120,000 people in England were admitted to hospital for fainting. Almost half of these were 75 years of age or over, showing that fainting becomes more common with age.
Outlook
Around a third of people who have fainted may faint again within three years. In general, the more someone faints, the more likely they are to faint again.
People who faint are at considerable risk of injury when they fall to the ground. Nearly a third of people experience minor bruises or cuts after a fall. Less commonly, people may fracture a bone or the faint could cause a car accident.
It is important that a healthcare professional investigates the cause of a fainting episode to rule out heart conditions (see Fainting - diagnosis). Treatment for fainting involves:
- avoiding the triggers of fainting, for example, avoiding hot and crowded environments
- being prepared to deal with fainting, for example, spotting the warning signs of fainting, such as feeling lightheaded, and lying down to increase blood flow to the brain
See Fainting - treatment for more information about what to do if someone is about to faint or has fainted.
