Recent studies suggest a possible link between narcolepsy and autoimmune disease. Although the exact causes of narcolepsy remain a mystery, it is known that environmental factors and genetic factors can both increase a person’s risk of developing the condition. Such is also the case with many autoimmune diseases.
Autoimmunity occurs when your immune system, designed to protect you from outside germs, attacks your own cells and tissues instead. If you have an autoimmune disease, your body thinks your immune cells, tissues, and organs are invading germs capable of causing you harm. In response, your immune system kicks in to protect you from what it thinks is an invading threat.
Narcolepsy is a chronic sleep disorder characterized by excessive daytime sleepiness and hallucinations. The condition is further broken down into type 1 narcolepsy and type 2 narcolepsy. Narcolepsy type 1 is defined as narcolepsy with cataplexy, or a sudden onset of muscle weakness associated with a lack of hypocretin in the brain. Hypocretin is a brain chemical produced in the hypothalamus that’s responsible for regulating sleep and wake cycles, including rapid eye movement (REM) sleep. As a result, narcolepsy can lead to insufficient restful sleep and poor daytime wakefulness, with REM occurring at times when it shouldn’t.
Narcolepsy may be an autoimmune disease. It’s believed that in people with narcolepsy, the immune system could be targeting and killing neurons (brain cells) that secrete hypocretin, leading to a severe deficiency in these hypocretin-producing cells. The following findings support this hypothesis.
In people who are genetically predisposed to narcolepsy, exposure to an environmental trigger may prompt the immune system to start attacking itself. A research team found strong evidence of an autoimmune response when they identified white blood cells in the immune system called CD4-positive T cells that targeted hypocretin. This group of T cells was found only in people with narcolepsy. Experts believe this targeted attack on hypocretin by a person’s own cells — an autoimmune attack — might lead to the development of narcolepsy.
Besides the finding that certain T cells occur uniquely in people with narcolepsy, other signs point to a link between immune response and the destruction of cells that produce hypocretin. Specifically, certain infections and vaccinations, which both mount immune responses, are associated with increased incidence (occurrence) of narcolepsy.
For instance, antibodies against streptococcus bacteria, which cause strep throat, are higher in people right after the onset of narcolepsy. This finding suggests that infection with strep is a likely trigger for narcolepsy.
Narcolepsy also tends to start late in the spring and early in the summer months, which could be explained by winter illnesses prompting the immune system into action.
Other evidence comes from the H1N1 (or swine flu) pandemic. Children in Scandinavian countries who received the Pandemrix vaccine developed during the H1N1 influenza pandemic were many times more likely to have narcolepsy. It’s believed that children predisposed to narcolepsy developed symptoms of the condition when their immune systems became activated by the vaccine.
The H1N1 influenza pandemic was also associated with more people being diagnosed with narcolepsy in China, contributing to the idea that an immune trigger — this time, infection with H1N1 itself — may lead to narcolepsy.
Researchers noted that some people with narcolepsy carry a gene, HLA-DQB1, related to immune function. Narcolepsy symptom severity is linked to this immune-related gene.
It’s common for people with autoimmune disorders to have more than one disorder at a time. Narcolepsy also has a pattern of having comorbid autoimmune conditions — such as multiple sclerosis, Crohn’s disease, psoriasis, and systemic lupus erythematosus — which may suggest that it is autoimmune as well.
Taken together, the evidence supports the theory that people predisposed to narcolepsy can become triggered when their immune system becomes exposed to an environmental cause. Immune overactivity could lead to narcolepsy.
Among other treatments for narcolepsy, research is being carried out to find therapies that target the immune system as immunologists and sleep medicine scientists continue to investigate the link between narcolepsy and autoimmunity.
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