These symptoms may affect performance on perception, memory, learning, executive functions, language, constructive abilities, voluntary motor control, attention, and mental speed. Affected individuals can complain of forgetfulness, confusion, or inability to think clearly. Excessive sleep (9 hours or more over a full 24-hour period), without feeling refreshed after waking. Daytime naps can be up to several hours and are also unrefreshing.Some studies have shown increased frequencies of palpitations, digestive problems, difficulty with body temperature regulation, and other symptoms in patients with IH. Anxiety and depression are frequent, likely as a response to chronic illness. A case series in 2010 found that peripheral vascular symptoms, such as cold hands and feet (e.g., Raynaud Syndrome), were more common in people with IH than in controls.Other autonomic dysfunctional symptoms, such as fainting episodes, dizziness upon arising, headaches (possibly migrainous in quality), food cravings, and impotence may also be correlated with IH. Researchers have found that people reporting IH symptoms report high levels of autonomic dysfunction on par with other conditions of autonomic failure (i.e., MSA and diabetes). As of June 2021, there is no evidence to suggest such symptoms are related to IH in any way. Causes
Unlike narcolepsy with cataplexy, which has a known cause (autoimmune destruction of hypocretin-producing neurons), the cause of IH is largely unknown.
The government still denies that there is any correlation between burn pits and health problems but the government has started an "Airborne Hazards and Open Burn Pit Registry" to begin tracking the health of veterans who were exposed to burn pits to see if there is a connection. E-cigarettes
The American Lung Association lists flavored e-cigarettes as a risk in 2016. Health Canada has, however seen no cases as of 2019. Public Health England writes that the association has come about as "some flavourings used in e-liquids to provide a buttery flavour contain the chemical diacetyl... however, diacetyl is banned as an ingredient from e-cigarettes and e-liquids in the UK." Mechanism
The underlying mechanism involves injury and inflammation of epithelial and sub-epithelial cells. These cells then lose the ability to repair the tissue, in particular they lose the ability to regenerate the epithelial or outermost layer, leading to the excess growth of cells that cause scarring. There are multiple pathways of the disease including fibrotic, lymphocytic, and antibody-mediated that have been described. However, while each pathway has a more unique starting point and cause, the result is still injury and inflammation leading to scarring of the lung tissue. The scarred tissue then makes the expiration phase of respiration more difficult, leading to air not being expelled from the lungs. This is termed "air-trapping", which can be seen on medical imaging. Since the scarring is non-reversible, the disease generally does not improve over time, and depending on the inciting can progress to death.