The patients may also struggle to sleep at night

The only definitive difference of type
2 narcolepsy is the absence of cataplexy in patients. However, if Type 2
develops cataplexy, it will be reclassified to type 1 narcolepsy. Type 2
usually associates with less severe symptoms with normal levels of hypocretin
and the condition does not get triggered by strong emotions.

Type 2 narcoleptics experience a daily
incontrollable urge to sleep during daytime. Even if patients feel refreshed
from previous rest they will feel fatigued after a short while. Both type 1 and
type 2 narcolepsy may also suffer from sleep paralysis and hypnagogic
hallucinations. The average sleep for both types are around 8 hour during
daytime. Although around 20% people with type 2 can sleep for longer periods. Conversely,
patients may also struggle to sleep at night developing a fragmented sleeping
pattern. This can negatively affect the daytime sleepiness and increase fatigue.
During their day sleep, the patients are immune to traditional wake-promoting
treatments.

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Narcolepsy is diagnosed using Multiple
Sleep Latency Test (MSLT) and check for sleep onset Rapid Eye Movement Period
(SOREMP). The MSL Test measures the daytime sleepiness by the rate of sleep after
a nap period. On the other hand, SOREMP test of REM sleep after Nap period (sleep
onset). Narcolepsy is identified using International Classification of Sleep Disorders
(ICD-3) criteria. Type 2 can be classified by five criteria:

·        
Excessive sleep
periods during the day, occurring at least for 3 months

·        
No cataplexy in
patient

·        
Narcoleptics
experience a mean sleep latency is around 8 minutes. Type 2 narcolepsy is
present if the patient has been diagnosed with at least two or more SOREMPs,
during MSLT.

·        
The patient with
type 2 will have cerebrospinal fluid (CSF) hypocretin-1 not measured or have
higher concentration than 110pg/ml. The CSF test can be conducted later in
life. If concentration resting at 110 pg/ml or lower, the condition is diagnosed
as type 1 narcolepsy.  

·        
Patients can only
be diagnosed with type 2 when they have a positive MSL and without any other
sleep disorders or side effects from medications.

Narcolepsy is categorised after 15
minutes of REM sleep. During this period, type 2 patients can experience hypnagogic
hallucinations.

Not much is known about the pathophysiology
of type 2 narcolepsy due to the rarity of disease and research. There are links
between in the anomaly in chromosome 4q13-q21 which may be associated with type 2, although the exact
cause is unknown. There is a research by Barateau et al. which states that unlike
type 1, there is a higher correlation of autoimmune diseases and type 2 narcolepsy.
 

 

 

Prevalence

Narcolepsy is a relatively rare disease
which affects 19-56 per 100,000 people throughout Europe and USA. Narcolepsy
with cataplexy or type 1 is commonly seen to be present in patient in around
60-81%.

Since the disease is so rare, it
usually goes unnoticed in the public. The symptoms of narcolepsy are commonly
mistaken for depression, epilepsy or side effects from medications. Most patients
suffers at least one of the four main symptoms: 
Hallucinations, sleep paralysis, cataplexy or excessive daytime sleepiness.
However only 20% of the patients are diagnosed with all four major symptoms.

Narcolepsy is widely distributed in
the world and is also more common than cystic fibrosis.

Figure 1. The graph show an estimation
of number of people affected by narcolepsy. The data does not show the comparison
of the people affected in contrast to the overall population. (Source: Data research by Statistic Brain research institute
on May 3, 2017.)

Narcolepsy UK research indicates that
the condition affects around 25,000 people. The condition affects 1 in 25,000
people in Britain, substantially lower than Japan (about 1 in 600). The study states
this excessive daytime sleepiness can cause up to 20% of roadside accident in
UK.

 According to Minnesota County studies,
estimates that Type 1 narcolepsy is prevalent in 25-50 per 100,000 people. In
contrast, Type 2 has not been studied in-depth, but is expected lower than type
1; around 20-34 in 100,000. In 2017, around 200,000 have been estimated to have
narcolepsy, 0.07% of the country. Only 0.01% out of 0.07% have gone to a doctor
for medical diagnosis.

The disease is neither gender of age
specific, although there is a greater occurrence in men than women. The first
signs of symptoms can normally be seen in teens to young adult. However,
narcolepsy can develop in children as young as 3 years old.