Chronic daily headache (CDH) is a descriptive term that encompasses several different headache diagnoses.

Epidemiology:

• Chronic daily headache affects 4% of the adult population in the United States and around the world.
• The vast majority of CDH patients suffer from either chronic migraine or chronic tension-type headache.
• Chronic daily headache results in significant pain and suffering, reduction in quality of life, and enormous economic costs to society.

Causative Factors:

• Major life changes (residence change, marital status, etc.) have been associated with the onset of CDH.
• Non-modifiable factors that increase the risk for CDH include female sex, low socioeconomic status, unmarried, history of head or neck trauma, and the presence of comorbid pain disorders.
• Modifiable risk factors for CDH include obesity, snoring and other sleep disorders, high caffeine intake, smoking, and overuse of abortive headache medications.

Similar to all headache types, it is essential to exclude a secondary headache as the cause of CDH. Depending upon the clinical history and examination findings, further diagnostic testing may or may not be necessary. Although a complete list of causes for secondary CDH would be exhaustive, summarizes

If secondary headaches are ruled out, the clinician must determine the type of primary CDH the patient has. Chronic migraine, chronic tension-type headache, new daily persistent headache, hemicrania continua, and medication overuse headache are discussed in this review. Although medication overuse headache is a secondary CDH, it is included here because of the important contribution to primary CDH.

Reference: http://www.medscape.com/viewarticle/723842?src=mp&spon=34