Disability in chronic daily headache: state of the art and future directions.

Aim of this literature review is to summarize the most relevant research findings on disability in subjects with chronic daily headache (CDH) and chronic migraine (CM) measured with the MIDAS and the HIT-6, and to address issues for further research in the field. Research strategy aimed to find papers published after 2001 that focused on disability in patients with CDH, CM and transformed migraine. Both, general population surveys or clinical series were included if they reported total scores, or distribution of the different disability levels, derived from the MIDAS and/or from the HIT-6. Fifteen papers were selected. Studies demonstrated that these subjects report a remarkable impact on functioning, with high disability scores, and reduced ability in work and non-work activities. Modern definitions of disability conceptualize it as the result of the interaction between a health condition and environmental factors. Research strategies should therefore recognize that disability may represent a global evaluation which should be added to more specific endpoints, using instruments that measure disability in a multi-dimensional way, such as the WHO-DAS II.