Migraine Headaches: Maybe Not So Bad for the Brain after All?
26 Apr, 2007 01:56 pm
There is an urban myth circulating about migraine headaches, namely that they result in dysfunction of the central nervous system and may ultimately cause accelerated cognitive decline over time.
So the question is: do migraine headaches result in cognitive dysfunction? The word ‘cause’ is a tricky word in medical research which we try to avoid since proving ‘cause’ is difficult. So we’ll ask a simpler question: do individuals with migraine headaches show evidence of cognitive dysfunction and does it worsen over time? At this point, an expert in neuroimaging may assert that dysfunction is likely since there is evidence that migraineurs have alterations in measures of cerebral blood flow and evoked potentials (9-11) , and are at increased risk for subclinical brain lesions (12, 13) and stroke (14). These are all valid arguments, but if and how alterations in cerebral blood flow and evoked potentials translate into cognitive dysfunction, however, are up to debate. This brings us back to our original question of whether there is tangible evidence of cognitive dysfunction in migraine.
Based on early studies, the cumulative effects of migraine attacks are hypothesized to result in subtle central nervous system dysfunction due to repeated vascular insult (15) . There is a theory called ‘cognitive reserve’, which states that brain injury may result in apparent cognitive deficits after a certain threshold of damage has been achieved (16) . If this theory is true, then the association between migraines and cognitive deficits would be most apparent in individuals who have had longer histories of headache attacks.
To answer our question above concerning the association between migraine headaches and cognitive functioning, we compared change in general cognitive functioning and memory performance over approximately 12 years in middle-aged and older individuals with and without a lifetime history of migraine headaches using a sample from The Baltimore Epidemiologic Catchment Area Study (17).
Our results were surprising, and in direct contradiction to what I originally had hypothesized. At baseline, migraineurs did score lower on tests of immediate and delayed memory, but declined by less over time as compared to those without migraine headaches. These associations were specific to migraineurs with aura, who declined by 1.26 and 1.47 words less on the 20-word immediate and delayed recall tests over the 12 years of follow-up. On a test of general cognitive functioning, called the Mini-Mental State Exam (MMSE), the effects of migraine headaches, specifically with aura, were restricted to those over age 50. Among those under age 50, migraineurs with aura declined at the same rate on the MMSE as those individuals without migraines. However, among those over age 50, migraineurs with aura declined by 0.99 points less over the follow-up. All results were statistically significant.
What exactly does this all mean? The clinical significance is the absence of any evident deficiencies on the MMSE and the other measures between those with and without migraine headaches. In fact, those with migraine may be declining on these measures less over time. There are numerous reasons for this result, including changes in diet and behavior adopted in order to curb migraine attacks, and self-medication with non-aspirin NSAIDS ( Non-steroidal anti-inflammatory drugs) , which have previously been shown to be protective against cognitive decline. We did attempt to assess whether these factors could be explaining the decreased decline over time in migraineurs, and found that they did not. However, our dataset was not the most adequate for this purpose. It is also possible that there is something about the biology underlying migraine headaches may give rise to mechanisms that ultimately protect against the loss of cognitive function. Certainly that would be great news for those with migraine headaches, perhaps a little consolation for their suffering.
Amanda Kalaydjian,, PhD MS completed this work at Johns Hopkins School of Public Health in Baltimore, MD, and is currently a research fellow at the National Institute of Mental Health in Bethesda, MD.
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