North Staffordshire Headache Survey: development, reliability and validity of a questionnaire for use in a general population survey.

The North Staffordshire Headache Survey aims to measure the effect and impact of headaches, medicine use and healthcare utilization in a general population sample. A self-reporting questionnaire was piloted in a general population sample, with reliability being tested in a sample of pilot responders after one month and validity by comparing pilot responders with primary and secondary care headache consulters. One hundred and twenty-two (61%) responded to the pilot survey, with 56% of items having completion rates of 90% or more, and tests showed good internal consistency (>90%). One-month test-retest data showed good agreement, though questions relating to specific time periods (with partial or no overlap between survey periods) showed expected lower agreement. The headache consulters reported greater frequency, duration and severity of headaches than the population sample suggesting good construct validity. Results from these studies indicate that the questionnaire is a reliable and valid instrument to collect data about headaches in the general population.