While the rates, risk factors, and impact of migraine transformation from an episodic to chronic pattern are known, a recent publication, stemming from data from the American Migraine Prevalence and Prevention (AMPP) study, has now documented the incidence, predictive factors, and potential significance of remission from chronic migraine (CM) to episodic migraine (EM)¹.

 

Approximately 6-9% of adult men and 18-24% of adult women in the United States experience migraine. Chronic migraine, arbitrarily defined as the presence of 15 or more headache days per month for at least 3 months, affects 2.2% of the American population, with 2.5% of EM sufferers converting to CM each year.  Epidemiology studies illustrate that individuals with CM tend to be older, as well as have co-morbid anxiety and depression, and lower levels of education and household income. A high baseline headache attack frequency, caffeine overuse, obesity, overuse of medications (particularly opiates and butalbital-containing compounds), stressful life events, and snoring are risk factors for the progression of migraine from an episodic to a chronic and daily or near-daily pattern^2,3.

 

The AMPP, a longitudinal, prospective, population-based survey, has been useful in shedding light on various aspects of migraine, including demographics, symptomatology, co-morbidities, headache-related disability, and issues related to heath care utilization. This particular analysis considered the responses from 383 individuals with CM who filled out the initial 2005 AMPP questionnaire and their follow-up information over the next two years. The data revealed that 130 (34%) continued to meet criteria for CM two years later, while 100 (26%) saw a reduction in headache frequency such that they were experiencing less than 15 days of headache per month in both 2006 and 2007. Not unexpectedly, remission of CM to EM was associated with not only pain and symptom improvement, but also a reduction in headache-related disability and an improved quality of life. This report shows us that the natural history of migraine is fluctuating and those with a high frequency of headaches move in and out of CM, perhaps regardless of treatment. 

 

Interestingly, the two predictive factors for remission were the baseline headache frequency (individuals with 15-19 headache days per month did better than those with 25-31 headache days per month) and the absence of allodynia, a term used to describe discomfort caused by light touch, mild pressure from clothing, and other stimuli not typically considered to be painful. These study outcomes support existing research about migraine. Several papers have shown that changes occur in brain metabolism and neuronal activity with CM⁴. From a clinical standpoint, these cellular changes translate into more frequent headache days and the presence of allodynia, the two features which suggest a reduced possibility of migraine remission. Given that CM remission is linked with an improved quality of life as well as reduced headache-related disability and associated costs, migraine reduction is a valuable goal. Research targeting improving our understanding of migraine pathophysiology plays a vital role in devising new treatments.  

 

Surprisingly, per this study, the influence of preventative medications was not clear, as their use did not lead to migraine remission. The authors offered several hypotheses for the perceived lack of benefit of prophylactic drugs – those on migraine preventatives may have had other factors playing a role that reduced their chance of remission, or the benefit of medications may have been off-set by other, insufficiently measured, confounding issues. Moreover, data regarding optimizing treatment, including medication dosing, appropriate medication choice for a given patient, and patient compliance was also not part of the study. These particular findings regarding medications could be due to a limitation of the study, and warrant additional investigation. Other clinical trials and experience tell us that patients with CM on a preventative medication see a reduction in headache frequency and severity, and are also less disabled by migraine.

Rashmi Halker, MD
Mayo Clinic College of Medicine
Phoenix, AZ