The MIDAS questionnaire has been used in Spanish populations to assess headache-related disability [8–10]. However, to the best of our knowledge, there is no validated Spanish version of the questionnaire. Therefore, this is the first study that analyzes the clinimetric properties of the Spanish version of the MIDAS questionnaire. Our results in university students have shown a factorial structure composed of two factors, good internal consistency data, results ranged from good to excellent in test-retest reliability, and a moderate correlation with PCS-12 in the concurrent validity analysis of the questionnaire. Therefore, our results evidence that the Spanish version of the MIDAS questionnaire is a valid and reliable instrument to measure headache-related disability.
Our results showed a different factorial structure to that one proposed by the original authors . Unlike the original structure, the PCA clearly identified two factors that explained near 90% of the variance. The first factor was composed of items that imply stop doing activities that you should do due to migraine (items 1, 3, and 5), such as work assistance, performance of housework or assistance to social activities. The second factor was composed by items that imply a decrease of 50% in the performance of both work and domestic tasks because of migraine (items 2 and 4). This two-factor structure is indicative of the different influence that migraine has on personal performance and, consequently, on disability.
In our population, near of two thirds of women and men presented any kind of disability due to migraine, which were related with decreased physical quality of life. These results are in agreement with previous studies [17, 18]. Also, several cognitive functions, such as processing speed, attention, memory, verbal skills, and executive function, are negatively affected by migraine  and are related to disability level, having a negative impact on daily life activities . In the present study, the first factor of the factorial structure included all items that reflected a higher cognitive function affectation by migraine, and consequently supposed a higher disability level, while the second factor reflected a lower affectation of the cognitive function.
The reliability parameters of the Spanish version of the MIDAS questionnaire were satisfactory as a whole. We have obtained good internal consistency results as shown in previous studies [17, 18, 21–23], including the most recent works [24, 25]. Results from the test-retest reliability analysis ranged from good to excellent. This analysis also showed that the additional items of the questionnaire are reliable and provide additional information that may be helpful for the clinician, coinciding with the authors of the questionnaire . The results obtained are in agreement with the way of measuring headache-related disability proposed by the original authors, although the factorial structure shown in the present study was different. The factorial structure obtained suggests the possibility of assessing headache-related disability in another way, since cognitive functions are affected by migraine in a different level, regardless its severity, thereby generating different disability levels that may lead from absenteeism to presentism .
The results of the present study show good clinimetric properties of the Spanish version of the MIDAS questionnaire, evidencing that this version is a consistent and reliable measure tool.
This study has several limitations. Although the prevalence of migraine is high in the student population, the results obtained can only be considered valid for this population. Another limitation is that the results may be only valid for the Spanish population because of the differences in structure and organization of the educational systems of different countries.
In future studies, the clinimetric properties of the MIDAS questionnaire should be analyzed in different populations and countries. It would be also advisable to examine the relation between headache and other concomitant disorders such as neck pain or dizziness, as well as to analyze the factors related to the presence of headache in university students and the impact that this disorder may have on this population.