The test-retest reliability of the German version of the HDQ will be tested to assess the reproducibility of the test results with a stable condition of the participants over a short period of time. For this purpose, it is planned to administer the questionnaire twice in row at an interval of 48 - 72 hours to headache patients in outpatient physiotherapy. The chosen setting limits the sample to a common intervention measure (physiotherapy), so that primary and secondary headache types can be included and the requirements of the original study can be maintained. In the period between the two tests, subjects should not receive physiotherapy, because it can often have different effects on headache. This can lead to uneven changes in the sample and affect the variance of the test results. However, subjects are allowed to take their usual medications. To avoid recall bias, an online survey tool (RedCAP) to conduct the questionnaire will be used. It is designed so that, only one question appears per slide, no overview of responses is allowed and the questions are displayed in a different order at the second testing. The lower prevalence of headaches after the age of 65 years is taken into account in the inclusion criteria.
a translated and cultural adapted version of the HDQ will be tested on two occasions with headache patients who are currently in physiotherapeutic treatment due to their headache condition