Participant details and associated health care utilisation were collected as part of the postal survey in 2000. Headache characteristics were self-reported at the time of interview except for severity which was assessed using the Chronic Pain Grade during the postal survey in 2000.
§Associated health care utilisation in the last year looked at whether participants had visited a general practitioner (GP), hospital specialist (HS), physical therapist (PT) or alternative therapist (AT) and whether they had used prescription medicine (PM), non-prescription medicine (NPM) or alternative medicine (AM).
* Level of education (No qual = no formal education qualification)
** Socio-economic class (1 = highest social class, 5 = lowest social class. M = manual, N = non-manual)