Headaches are common 1. Severe, chronic headaches affect 45 million Americans. Headaches result in more than 8 million doctor visits per year, according to The National Institute of Neurological Disorders and Stroke. Some of these headaches occur at night, and have very specific characteristics and causes.
Hypnic headaches, or "alarm clock" headaches, only occur during sleep. They typically awaken the sufferer at the same time each night, notes the Mayo Clinic. The pain is mild to moderate, and commonly lasts from 15 minutes to two hours or longer. The cause is not known. The headache occurring at the same time each night suggests a link to the circadian rhythms and sleeping/wake cycle, according to an article by E. Kerr and colleagues in the May 2006 "Ulster Medical Journal." Hypnic headaches commonly occur during REM, or dream, sleep. A decrease in melatonin, a hormone that affects sleep, which occurs with age, may play a role.
Cluster headaches typically strike two to three hours after sleep begins. Symptoms accompanying the headache can include teary eyes, a flushed face, swelling around one or both eyes and a stuffy nose. The headache reaches its peak within 15 minutes and lasts from 30 minutes to two hours, says Medline Plus 5. Typically, cluster headaches occur regularly for months, alternating with headache-free periods 5. They can also be chronic.
Although the exact cause of cluster headaches is unknown, researchers believe a rapid release of serotonin or histamine may be factors.
Increased pressure from a tumor within the skull causes headaches, and is a common first symptom of a brain tumor. Typically, the headache becomes more frequent until it is constant, according to The Merck Manuals Online Medical Library 4. It is usually worse when lying down, and may awaken the sufferer from sleep.
Exploding Head Syndrome
Exploding head syndrome is a rare disorder that leads people to complain of a headache that awakens them during the night, according to the National Headache Foundation 2. Sufferers complain of being awakened by a loud, explosive sound in the head that is very frightening but not painful. This syndrome is actually a sleep disorder, and is treated with a medication called clomipramine.
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