Development of chronic daily headache: a clinical study.

We studied the development of chronic daily headache in 258 headache practice patients, 50 men and 208 women. Chronic daily headache was defined as headaches occurring at least 5 days per week for at least 1 year. Twenty-two percent of the patients had daily headaches from the onset, and 78% initially experienced intermittent headaches. Of the patients with initially intermittent headaches, 19% experienced an abrupt transition into daily headaches and 81% a gradual one. The distribution of the age of daily headache onset was the same in the patients with daily headaches from the onset and in those with initially intermittent headaches but with abrupt transition into daily headaches. The distribution of the circumstances of daily headache onset was also the same in the groups. The most common circumstance of abrupt onset of daily headaches was head, neck, or back injury, in 61% caused by a motor vehicle accident. In the patients with initially intermittent headaches but with gradual transition into daily headaches, the transition took an average of 10.7 years.