Are there limitations of headache days used alone as a diagnostic tool?

News from the European Headache Foundation Congress
Enrico Greppi Award for study supported and funded by Allergan

The award is supported by the Italian Society for the Study of Headaches (SISC) and endorsed by the EHF.

2017 Enrico Greppi Award Winner: Fluctuations in Episodic and Chronic Migraine Status Over the Course of One Year: Implications for Diagnosis, Treatment and Clinical Trial Design1

Relatively little is known about the stability of a diagnosis of episodic migraine (EM; <15 headache days) or chronic migraine (CM; ≥15 headache days) over time. The researchers in this study examined natural fluctuations in self-reported headache frequency as well as the stability and variation in migraine type (EM and CM).1

The researchers analysed longitudinal data from the Chronic Migraine Epidemiology and Outcomes (CaMEO) Study in US adults with CM and EM to better characterise within-person change in the headache days. At baseline 5,464 respondents had EM, 525 respondents had CM. Using negative binomial repeated measures regression models (NBRMR) they found that the rate of headache days increased 26% increase per observation wave for CM compared to EM (rate ratio 1.26; 95% CI, 1.2–1.33).1

Key findings include:

  • There are substantial variation in headache day frequency in people with EM and CM followed at three-month intervals1
  • Nearly 75% of people with CM experienced less than 15 headache days during assessment at some time point during the 12-month period1
  • Transitions from EM to CM are more common than previously observed1
  • This natural variation should be considered when diagnosing, treating and studying CM1

Headache day diagnosis is often assumed to be relatively stable for an individual, however this research suggests that headache frequency can be variable. This could impact a patient’s diagnosis, potentially moving them over time between the CM and EM diagnostic categories. For example, when a patient transitions from 16 headache days per month to 14 days per month, their diagnosis may change, but the underlying pathophysiology of their disorder does not change.1

Importantly, these findings should prompt clinicians to assess how they interpret the effects of preventative treatment in practice. Clinicians often rely on a short term improvement in headache days to determine treatment effectiveness, but these results show that a variation in headache days may not be related to treatment, and that a longer term assessment may be required.1

Richard Lipton, MD, Vice Chair of Neurology, Albert Einstein College of Medicine, and an author on the paper comments: “There is a traditional bright line of 15 headache days per month that separates people with episodic migraine from those with chronic migraine, but people with migraine experience striking fluctuations in the frequency of their headaches. Therefore headache days alone, in any particular time period, may not be sufficient to distinguish between episodic and chronic migraine. More data is needed to fully understand the underlying biological differences.”


  1. Serrano D et al. Fluctuations in episodic and chronic migraine status over the course of 1 year: implications for diagnosis, treatment and clinical trial design, The Journal of Headache and Pain, 2017, 18:101