The main symptom of hypersomnia is excessive daytime sleepiness (EDS), or prolonged nighttime sleep,[7] which has occurred for at least 3 months prior to diagnosis.
[9] According to the American Academy of Sleep Medicine, hypersomniac patients often take long naps during the day that are mostly unrefreshing.
[13] After it is determined that excessive daytime sleepiness is present, a complete medical examination and full evaluation of potential disorders in the differential diagnosis (which can be tedious, expensive and time-consuming) should be undertaken.
When specific treatments of the known condition do not fully suppress excessive daytime sleepiness, additional causes of hypersomnia should be sought.
Myotonic dystrophy is often associated with SOREMPs (sleep onset REM periods, such as occur in narcolepsy).
However, the associated symptoms of headaches, memory loss, and lack of concentration may be more frequent in head trauma than in idiopathic hypersomnia.
Hypersomnia can be secondary to disorders such as clinical depression, multiple sclerosis, encephalitis, epilepsy, or obesity.
[17] In some cases it results from a physical problem, such as a tumor, head trauma, or dysfunction of the autonomic or central nervous system.
[17] Sleep apnea is the second most frequent cause of secondary hypersomnia, affecting up to 4% of middle-aged adults, mostly men.
Upper airway resistance syndrome (UARS) is a clinical variant of sleep apnea that can also cause hypersomnia.
In fact, two studies showed no correlation between PLMS and objective measures of excessive daytime sleepiness.
[18] "Other sleep alterations, such as periodic limb movement disorders in patients with spinal cord disease, have also been uncovered with the widespread use of polysomnography.
The CDC states that people with ME/CFS experience post-exertional malaise, fatigue, and sleep problems (among other symptoms).
[21] Also, researchers have shown that disrupting stage IV sleep consistently in young, healthy subjects causes a significant increase in muscle tenderness—similar to that experienced in "neurasthenic musculoskeletal pain syndrome".
[22] Chronic kidney disease is commonly associated with sleep symptoms and excessive daytime sleepiness.
About 50% of dialysis patients have hypersomnia, as severe kidney disease can cause uremic encephalopathy, increased sleep-inducing cytokines, and impaired sleep efficiency.
[23] Most forms of cancer and their therapies can cause fatigue and disturbed sleep, affecting 25-99% of patients and often lasting for years after treatment completion.
Hypersomnia can also develop within months after viral infections such as Whipple's disease, mononucleosis, HIV, and Guillain–Barré syndrome.
[8] Behaviorally induced insufficient sleep syndrome must be considered in the differential diagnosis of secondary hypersomnia.
Therefore, a patient's complete medication list should be carefully reviewed for sleepiness or fatigue as side effects.
The complaint of excessive daytime sleepiness in these conditions is often associated with poor sleep at night.
[29] Kleine-Levin syndrome is characterized by the association of episodes of hypersomnias with behavioral, cognitive and mood abnormalities.
[31] Unlike Kleine-Levin syndrome, hyperphagia and hypersexuality are not reported in people with menstrual-related hypersomnia, but hypophagia could be present.
[38] During that test, patients have a series of opportunities to sleep at 2-h intervals across the day in a darkened room and with no external alerting influences.
[39][40] The MSLT is often administered the day after recording the polysomnography, and the mean sleep latency score is often found to be around (or less than) 8 minutes in idiopathic hypersomnia patients.
Actigraphy, which operates by analyzing the patient's limb movements, is used to record the sleep and wake cycles.
[41] An actigraphy over several days can show longer sleep periods, which are characteristic for idiopathic hypersomnia.
[44] Modafinil has been found to be the most effective drug against the excessive sleepiness, and has even been shown to be helpful in children with hypersomnia.
[56] Hypersomnia affects approximately 5% to 10% of the general population,[57][58] "with a higher prevalence for men due to the sleep apnea syndromes".