Disability pattern in chronic migraine with medication overuse: a comparison with migraine without aura.

OBJECTIVES: To assess headache-related disability in chronic migraine with medication overuse (CMO), as defined by Silberstein and Lipton (1996, 2001) in comparison to that caused by migraine without aura, investigating similarities and differences in disability patterns in these two conditions.

BACKGROUND: It is well known that migraine has a marked impact on daily activities. Less information is available on the functional consequences of chronic migraine.

METHODS: This was a prospective study on 247 patients with CMO and 264 with migraine without aura. All completed the validated Italian version of the Migraine Disability Assessment questionnaire (MIDAS). The MIDAS total score and scores of each question (investigating total or partial inability to perform different daily activities) were evaluated, and compared in the two groups using the Mann-Whitney rank sum test. We also evaluated the number of missed days (question 1) and days with significantly reduced effectiveness at work (question 2) and in nonwork activities (questions 3, 4, and 5), using descriptive statistics.

RESULTS: MIDAS total score in the CMO group was rather high (mean 84.1, median 70) and significantly higher than in the migraine group (mean 23.4, median 19). CMO patients also reported higher scores than migraine patients in MIDAS questions investigating disability in different domains, the differences being highly significant for questions 3, 4, and 5. In both CMO and migraine the number of days with total or significant disability in nonwork activities was higher than the number of days with total or significant disability in work activities, and days spent at work with significantly reduced effectiveness were more than work days missed.

CONCLUSIONS: Our findings show that CMO has a profound effect on patients' daily functioning. They suggest that differences between CMO and migraine are mainly quantitative, while the two groups are similar in terms of disability pattern. These results are consistent with the fact that CMO may be an evolution of episodic migraine, characterized by increase in headache frequency and more evident disability in performing different daily duties.