Abstract
To ensure reproducibility in research quantifying episodic migraine attacks, and identifying attack onset, a sound theoretical model of a migraine attack, paired with a uniform standard for counting them, is necessary. Many studies report on migraine frequencies—e.g. the fraction of migraine-days of the observed days—without paying attention to the number of discrete attacks. Furthermore, patients’ diaries frequently contain single, migraine-free days between migraine-days, and we argue here that such ‘migraine-locked days’ should routinely be interpreted as part of a single attack. We tested a simple Markov model of migraine attacks on headache diary data and estimated transition probabilities by mapping each day of each diary to a unique Markov state. We explored the validity of imputing migraine days on migraine-locked entries, and estimated the effect of imputation on observed migraine frequencies. Diaries from our patients demonstrated significant clustering of migraine days. The proposed Markov chain model was shown to approximate the progression of observed migraine attacks satisfactorily, and imputing on migraine-locked days was consistent with the conceptual model for the progression of migraine attacks. Hence, we provide an easy method for quantifying the number and duration of migraine attacks, enabling researchers to procure data of high inter-study validity.
Highlights
To ensure reproducibility in research quantifying episodic migraine attacks, and identifying attack onset, a sound theoretical model of a migraine attack, paired with a uniform standard for counting them, is necessary
While detailing our proposed Markov chain model, we argue that migraine days separated by a single migraine-locked day—a day in a patient’s migraine diary that is immediately preceded by and succeeded by migraine days—should routinely be considered as a single attack that includes the migraine-locked day
Imputing migraine on migraine-locked days. This issue does not necessitate any new hypotheses; it merely provides an alternative way of categorising days as ‘migraine days’ that is more in accord with the pathophysiology of migraine
Summary
To ensure reproducibility in research quantifying episodic migraine attacks, and identifying attack onset, a sound theoretical model of a migraine attack, paired with a uniform standard for counting them, is necessary. We wish to elaborate on how the most current knowledge about the course of a migraine attack translates into a certain, well-defined, standard for recording attack data To this end we quantify the conditional probability of the occurrence of a migraine day continuing into the day. We test the robustness of one assumption some migraine researchers rely on: that the probability of experiencing a migraine headache on any given day is independent of the previous day’s ‘migraine status’[1,2]. This assumption has broader implications if adopted to investigate migraine triggers. If a patient reports on three consecutive days migraine on the first, no migraine on the second, and migraine again on the third day, a clear standard for how to analyse these data in relation to the presence or absence of candidate triggers is clearly crucial
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