Nighttime headaches: What causes them?

Q: What causes nighttime headaches?

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Nighttime headaches can have many causes.

Sometimes migraines and cluster headaches awaken a person from sleep. In other cases, nighttime headaches are actually hypnic — or "alarm clock" — headaches. Hypnic headaches begin only during sleep, usually awakening the person at the same time every night. Some people also have daytime naps interrupted by hypnic headaches.

Hypnic headaches are most common after age 50. The pain can be mild to moderate and usually lasts from 15 minutes to two hours, but occasionally longer. The exact cause of hypnic headaches isn't known.

Less common but more serious causes of nighttime headaches may include:

• A sleeping disorder in which breathing repeatedly starts and stops (sleep apnea)
• Inflammation of the arteries in the head (giant cell arteritis)
• Bleeding on the surface of the brain (subdural hematoma)
• Brain tumor

If you have nighttime headaches or headaches that awaken you from sleep, see your doctor. Headaches are typically diagnosed based on a person's medical history and specific signs and symptoms. In some cases, imaging tests — such as computerized tomography — are needed as well. Treatment varies, depending on the type of headache and any underlying causes.