LONDON—Case reports and some epidemiological studies have pointed toward a connection between migraines and asthma. A large matched case-control study recently identified a relative risk (RR) of 1.59 for asthma in migraine patients, confirming the association and suggesting shared etiological origins for the two disorders.[1]

A history of migraine has been associated with increased asthma incidence among nonatopic patients. Furthermore, one study showed that asthmatic children were 5.5-fold more likely than nonasthmatic children to have a parent with history of migraine; another found that children of mothers who suffered migraines were more likely than offspring of migraine-free mothers to develop asthma. This evidence prompted David Strachan, MD, from St. George’s Hospital Medical School in London, and colleagues to examine the associations between asthma and migraine in an extensive national database of English and Welsh residents. A total of 64,678 potential migraine cases were classified into four categories:

• Category 1: at least one diagnosis and at least one prescription for migraine prophylaxis.
• Category 2: at least one diagnosis with at least two prescriptions for acute migraine attacks.
• Category 3: at least two diagnoses with at least two prescriptions for acute migraine attacks.
• Category 4: prescription of a ß-blocker for migraine prophylaxis.

Each migraine patient was matched (for age, sex, and practice visited) with a patient never diagnosed with migraine. When calculating RR for asthma, the researchers considered category 4 patients separately to avoid the possibility that the results might be confounded either by ß-blockers’ potential effects in exacerbating asthma symptoms or the contraindication of the drug class in asthmatic patients.

The RR for asthma was elevated among patients in categories 1, 2, and 3, but not among those in category 4. When patients in all four categories were considered together, the researchers found that migraine sufferers also had significantly elevated risks for chronic obstructive pulmonary disease (RR, 1.22), respiratory symptoms (RR, 1.85), eczema (RR, 1.56), and hay fever (RR, 1.67).

ASTHMA LINKED TO NONATOPIC ASTHMA

Interestingly, the association between migraine and asthma was stronger among those without hay fever than among hay fever sufferers (RR, 1.32 vs 1.19). Although the difference between the two groups did not reach significance, the result concurs with a previous cohort study’s finding that the association of asthma with migraine was limited to those with no history of atopy.

One explanation the researchers offer is “that migraine is more strongly associated with nonatopic asthma, which might also account for the raised risk for chronic obstructive pulmonary disease in migraine patients.” Thus, the connection between migraine and asthma may have less to do with the immunologic component of asthma than with bronchial hyperresponsiveness per se.

Their current data as well as previous work associating the two conditions “suggest a link between migraine (vascular reactivity) and asthma (bronchial reactivity) that is independent of allergic mechanisms,” the researchers argue. “A shared functional abnormality of smooth muscle in blood vessels and airways offers a plausible explanation for this link,” they offer.

—Mimi Zucker, PhD