Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The term hypersomnia refers to a large group of disorders characterized by excessive daytime sleepiness. Hypersomnia can be primary, such as narcolepsy (with and without cataplexy); idiopathic hypersomnia; and recurrent hypersomnias, or it can be secondary to another medical condition. Hypersomnia affects approximately 5% of the general population, with a higher prevalence for men due to the sleep apnea syndromes. Learn more about hypersomnia, its symptoms and treatment in the following pages.