Methodology of studies on the epidemiology of headache.

Headache is a common clinical condition. A correct evaluation of its frequency, characteristics and aetiology is a prerequisite for health care planning and for the implementation of preventive and treatment measures. Descriptive and analytic epidemiological studies are the basis to improve the knowledge of the burden of headache in the community. However, the results of the epidemiological studies are heavily dependent on the quality of the design, the correctness of the conduct and the appropriateness of the data analysis. A proper knowledge of the problems in the conduction and interpretation of the epidemiological studies helps the investigators to optimise the study protocols and the practicing physicians to critically view the published results.