Narcolepsy - Causes of narcolepsy

Many cases of narcolepsy are thought to be caused by a lack of the brain chemical orexin (also known as hypocretin), which regulates sleep.

This deficiency is thought to result from the immune system mistakenly attacking parts of the brain that produce this chemical.

However, this is not the cause in all cases.

Problem with the immune system

Normally, antibodies (proteins) are released by the body to destroy disease-carrying organisms and toxins. When antibodies mistakenly attack healthy cells and tissue, it's known as an "autoimmune response".

In 2010, scientists in Switzerland discovered that some people with narcolepsy produce trib 2 antibodies, which attack the orexin-producing areas of their brain. This results in a lack of orexin, and their brain not being able to regulate sleep cycles.

These research results help explain the cause of narcolepsy in many cases, but it doesn't explain why some people with the condition still produce near-normal levels of orexin.

Possible triggers

A number of factors may increase a person's risk of narcolepsy or cause an autoimmune problem, including:

• an inherited genetic fault
• hormonal changes, including those that occur in puberty or the menopause
• major psychological stress
• a sudden change in sleep patterns
• an infection, such as flu or a streptococcal infection
• having the flu vaccine Pandemrix (see below)

Research has yet to confirm whether all of these play a role in narcolepsy.

Pandemrix vaccine

Recent research has shown that there is an association between the use of the flu vaccine Pandemrix, which was used during the swine flu epidemic of 2009-10, and narcolepsy in children.

This risk is very small: researchers estimated the chance of developing narcolepsy after receiving a dose of the vaccine in the UK to be around 1 in 52,000.

However, as a result, Pandemrix is no longer given to people under the age of 20.

Impact of narcolepsy on sleep

The total time someone with narcolepsy spends sleeping is not necessarily different to that of people without the condition.

However, narcolepsy can significantly affect sleep cycles and quality of sleep.

Sleep consists of periods of different brain activity known as non-rapid eye movement (NREM) and rapid eye movement (REM). REM sleep is when brain activity starts to increase and dreaming may occur.

Most people go through several sleep cycles that consist of four stages of NREM sleep at first, followed by a short period of REM sleep.

If you have narcolepsy, this pattern is much more fragmented, and you may wake several times during the night. You may also experience REM sleep much earlier than normal after falling asleep, and you may experience effects of REM sleep, such as dreaming and paralysis, while you are still conscious.