health

One in three people faint occasionally. The problem occurs in people
of all ages, although it is most common in people over 65 years of age.
Fainting has many possible causes. Some of the more frequent ones are
described below.

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, individuals may have 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, which reduces blood flow to the brain, and
the person may faint.

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. People who take part in strenuous physical
activities under hot, humid conditions may experience this problem.

Standing up quickly
When most people stand up, the nervous system*
triggers a reflex response that increases the heart rate and blood pressure.
This response 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.