Sleep is the most natural thing to do, but for some people it is incredibly painful because when they sleep, a headache follows, which is called a sleep headache. Sleep headache was first reported by Raskin in 1988. In the 2004 International Classification of Headache, the diagnostic criteria for sleep headache were revised and it was included as a primary headache. It occurs most often over the age of 50 and its most important clinical feature is that the headache attacks during sleep and causes awakenings. Studies have found that sleep headache attacks occur in both the REM and NREM phases of sleep. Therefore, patients with sleep headache have changes in sleep architecture, mostly manifesting as difficulty falling asleep and increased awakenings during sleep.