How common are primary and secondary headaches?

Tension headaches are the most common type of primary headache; as many as 90% of adults have had or will have tension headaches. Tension headaches are more common among women than men.

Migraine headaches are the second most common type of primary headache. An estimated 28 million people in the United States (about 12% of the population) will experience migraine headaches. Migraine headaches affect children as well as adults. Before puberty, boys and girls are affected equally by migraine headaches, but after puberty, more women than men are affected. An estimated 6% of men and up to 18% of women will experience a migraine headache.

In the United States, migraine headaches often go undiagnosed or are misdiagnosed as tension or sinus headaches. As a result, many migraine sufferers do not receive effective treatment.

Cluster headaches are a rare type primary headache, affecting 0.1% of the population. An estimated 85% of cluster headache sufferers are men. The average age of cluster headache sufferers is 28-30 years, although headaches may begin in childhood.

Secondary headaches have diverse causes, ranging from serious and life threatening conditions such as brain tumors, strokes, meningitis, and subarachnoid hemorrhages to less serious but common conditions such as withdrawal from caffeine and discontinuation of analgesics.
Many people suffer from "mixed" headache disorders in which tension headaches or secondary headaches trigger migraine headaches.