A history of asthma may predict chronic migraine in individuals who have episodic migraine, according to a study published November 19 in Headache.
Because both conditions are prevalent — about 11.6% of the US population has migraine and 7.5% has asthma — comorbidity is likely, but a risk relationship has not been established. “Links between asthma and migraine had been reported, and people who practice headache medicine have noticed that a lot of patients with migraine also have asthma,” Richard Lipton, MD, director of the Montefiore Headache Center and the Edwin S. Lowe Chair in Neurology, Albert Einstein College of Medicine, Bronx, New York said.
At first, Dr Lipton, who is senior author on the paper, thought he was seeing a skewed sample of patients with both disorders who had been referred by primary care physicians uncertain of whether to prescribe propranolol to prevent migraine to patients with asthma. But then he noted other clues: “Leukotriene inhibitors have some effect in asthma and migraine, and both disorders involve inflammatory changes and changes in smooth muscle. In asthma, bronchoconstriction is caused by contractility of smooth muscle in the airways and inflammation of the airway linings. And in migraine there’s inflammation, and dilation and constriction of blood vessels. These mechanistic links suggested that the two conditions might be associated.”
Dr Lipton was already conducting the American Migraine Prevalence and Prevention (AMPP) study, so he added asthma questions. “Then we asked, ‘Does asthma predict worsening of migraine over time?’ Lo and behold, it did,” he said.
Link Apparent in Large Study
For the current study, lead author Vincent T. Martin, MD, codirector of the Headache and Facial Pain Program at the University of Cincinnati Neuroscience Institute in Ohio, and colleagues hypothesized that asthma is a risk factor for the transition from episodic to chronic migraine (15 or more headaches a month). Chronic migraine rarely occurs without episodic migraine first.
The researchers used data from the AMPP for 2008 and 2009. The instrument included a six-item asthma questionnaire from the European Community Respiratory Health Survey. Also, to investigate whether more severe asthma increased the likelihood of progressing to chronic migraine, the researchers developed a Respiratory Symptom Severity Score, ranging from no severity (zero positive responses), to low severity (one to two positive responses), moderate severity (three to four positive responses), and high severity (five to six positive responses). The AMPP asked about headache duration and frequency.
Of 4446 participants who had episodic migraine, 746 (16.8%) had asthma and 3700 (83.2%) did not. In 2009, new-onset chronic migraine developed in 2.9% (131/4446) of the cohort, which was the primary endpoint.
This group included 5.4% (40/746) of the asthma subgroup and 2.5% (91/3700) of the nonasthma subgroup. Participants with asthma had a greater than twofold risk for progression to chronic migraine compared with those without asthma, after adjusting for sociodemographic factors (including age, body mass index, sex, and income), headache frequency, and migraine preventive medication use (adjusted odds ratio [aOR], 2.1; 95% confidence interval [CI], 1.4 – 3.1).
Moreover, the risk appeared to increase as the number of asthma symptoms increased, but only those in the high asthma severity group exhibited a statistically significant increase in the odds of chronic migraine onset compared with those without asthma (aOR, 3.3; 95% CI, 1.7 – 6.2).
“If increasingly severe asthma symptoms increase the risk of progression to chronic migraine, then it is more likely that respiratory symptoms play a causal role,” Dr Lipton said. “While we found that overall presence of asthma about doubles the risk, the group with the most severe respiratory symptoms was more than three times as likely to develop chronic migraine as people free of asthma.” The apparent dose-response is similar to that for depression, he added. “Overall, depression a little less than doubles the risk of chronic migraine, but the highest depression triples risk.”
The other covariates, including medication overuse, headache frequency, and preventative medication use, were not associated with new-onset chronic migraine. Other risk factors for chronic migraine are obesity, allodynia, other pain disorders, and overuse of barbiturates and narcotics.
The decision to use migraine preventive medication in patients with asthma with episodic migraine is complex, Dr Lipton said. “Physicians should assess the overall profiles of risk factors for migraine progression and take them into account in treatment decisions. But I don’t think any studies have shown that if you identify people at high risk for migraine progression that treatment with migraine preventive medication prevents progression.” He also speculates that treating asthma with drugs that reduce inflammation may have a protective effect against migraine progression, if inflammation is the link.
The authors note several study limitations including unknown confounders, the fact that 90% of the participants were Caucasian, self-reporting on questionnaires, and the 1-year duration.