Causes

Manycases of narcolepsy are thought to be caused bya lack of the brain chemical hypocretin (also known as orexin), which regulates sleep.

This deficiency is thought to result fromthe immune system mistakenly attacking parts of the brain that producehypocretin. However, a lack of hypocretin isn't the cause in all cases.

Immune system problem

Normally, antibodies are released by the bodyto 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 thatsome people with narcolepsy produce antibodies against a protein called trib 2.

Trib 2 is produced by an area of the brain that also produces hypocretin. This results in a lack of hypocretin,which means the brain is lessable to regulate sleep cycles.

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

Possible triggers

Anumber 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 during puberty or the Testosterone deficiency (hypogonadism)
• major psychological stress
• a sudden change in sleep patterns
• an infection, such as swine flu or a streptococcal infection
• having the flu vaccine Pandemrix

Research is yet to confirm whether allof these play a role in narcolepsy.

Pandemrix vaccine

Recent research hasshown 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.

However, the riskis very small. Researchers estimate the chance of developing narcolepsy after receiving a dose of the vaccine is around1 in 52,000in the UK.

As a result of the findings, 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 isn't necessarily differentfrom that of peoplewho do not have the condition. However, narcolepsy can significantly affect sleep cycles and decrease the quality of sleep.

Sleep consistsof cycles of different brain activity known as non-rapid eye movement (NREM) and rapid eye movement (REM). During REM sleep, brain activity increases and dreaming may occur.

Normal sleep consists of three stages ofNREM sleep at first, followed by a short period of REM sleep, with NREM and REM sleep then alternating throughout the night. During the latter part of the night, REM sleep is more prominent.

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