71 Defining migraine days 3 Table 3. Number of MMD (mean ± SD) using the migraine characteristics with a duration of ≥ 4 hours is compared to using an adjusted minimum headache duration criterion of 30 minutes, in combination with migraine days defined by triptan intake or days with effective triptan response. In bold the number of MMD following our proposed definition. All triptan days Effective triptan days Total (n=1478) ≥ 4 hours 6.9 ± 4.9 6.5 ± 5.0 ≥ 30 minutes 7.4 ± 5.1 7.1 ± 5.1 CM patients (n=255) ≥ 4 hours 13.7 ± 5.5 13.5 ± 5.6 ≥ 30 minutes 14.4 ± 5.5 14.1 ± 5.8 HFEM patients (n=697) ≥ 4 hours 6.9 ± 2.7 6.4 ± 2.8 ≥ 30 minutes 7.4 ± 2.8 7.0 ± 2.9 LFEM patients (n=526) ≥ 4 hours 2.9 ± 1.6 2.6 ± 1.5 ≥ 30 minutes 3.1 ± 1.6 2.9 ± 1.6 CM = Chronic migraine is defined as ≥ 3 consecutive months with ≥15 headache days per month with ≥ 8 MMD. HFEM = High frequent episodic migraine is defined as ≥1 month with ≥ 8 MMD. LFEM = Low frequent episodic migraine is defined as < 8 MMD. DISCUSSION There is a need for consensus on the definition of a migraine day for clinical and research practices. In order to formulate a standardized definition, we compared four different definitions. We initially defined a migraine day based on the typical migraine headache and associated characteristics with a duration of ≥4 hours, or a day with triptan intake. We found that 14.1% of all identified migraine days were defined by triptan intake alone, and did not match all migraine characteristics. Headache duration was the most frequent missing criterion (66.6%) in these days defined by triptan intake alone, which is likely explained by the effectiveness of the triptan. Using a headache duration of ≥30 minutes resolves this issue, and results in only 5.4% increase in monthly migraine days (MDD) in which a triptan was not used. This 5.4% increase in migraine days equals on average a 0.45 day increase in MMD. Although shorter, the majority of migraine days identified by the adjusted duration criterion still have a headache duration of ≥2 hours. We propose to use the ≥30 minutes instead of ≥4 hour duration criterion, since all other migraine characteristics are still met, and the frequency of acute medication use seems similar as in migraine days defined by the ≥4 hour duration criterion. Since clinicians advise patients to take their acute medication at the onset of the migraine headache phase, it would be incorrect not to define an aborted attack as a migraine day. Defining too few migraine days should be avoided, since it can lead to an underestimation of the actual burden of patients, for example due to patients following the advice not to delay taking acute medication.
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