migraines salutaires ? Les migraines améliorent-elles la mémoire ?

http://www.nature.com/news/2007/070423/full/070423-3.html / Published online: 23 April 2007; | doi:10.1038/news070423-3

Migraines may slow memory loss

Sufferers show less cognitive decline as they age.

Heidi Ledford

A migraine is not just a headache, it is an über-headache - a pounding, queasy, searing pain that can incapacitate its victims for hours on end. And as if the pain weren't bad enough, sufferers were also thought to show diminished memory and verbal skills.

But new research now suggests that although migraines are sometimes associated with diminished cognitive skills, sufferers may in fact show less memory loss as they age than those who are migraine-free.

The results are puzzling, admits Amanda Kalaydjian of the National Institute of Mental Health in Bethesda, Maryland, who led the study. "We originally hypothesized that migraineurs would be doing worse," she says, "so I was really surprised."

Slower decline

More than 28 million people in the United States suffer from migraines, and women are three times more likely than men to have the condition. The cause is still unknown, and different theories have blamed nervous-system malfunctions, chemical imbalances, over-reactive blood vessels, or a combination of factors.

Meanwhile, attempts to catalogue the damage wrought by a lifetime of migraine attacks have met with conflicting results. Some studies suggest that migraineurs have poorer memories and less verbal ability than those without the condition, whereas other studies show no difference at all between sufferers and non-sufferers. Most of these studies were small and relied on patients in headache clinics, meaning that the study population can be skewed towards those with more severe cases of the condition, Kalaydjian points out.

Kalaydjian decided to test how cognitive function in migraineurs changes over time. She and her colleagues tested word recall and overall cognitive function in 1,448 people, including 204 migraine sufferers selected from a broad epidemiological study and not from headache clinics.

The results, published today in Neurology, show that sufferers do perform worse on memory tests than non-sufferers, both during the initial screens performed from 1993 to 1996 and in follow-up interviews in 2005. But although both groups tended to show signs of cognitive decline in the roughly 12 years between the two tests, many migraineurs did not decline as rapidly. In particular, the ability to remember specific words did not weaken as much in migraineurs who suffer from migraines with 'aura', the flashing lights, squiggly lines and other visual interruptions that accompany some migraines. And in other tests of cognitive function, migraineurs who were older than 50 did not weaken as quickly as people in the same age group who do not suffer from migraines.

Exactly why the migraineurs would be more protected from cognitive decline remains a mystery. "Since no one really knows what causes migraines, it's really difficult to say what about them may or may not decrease the cognitive decline," says Kalaydjian.

Brains trained?

One possibility is that lifestyle differences in those with migraines could have a protective effect. Migraineurs may take non-steroidal anti-inflammatory medications such as ibuprofen to relieve their pain, and some studies have suggested that these drugs may help to protect against cognitive decline. People with migraines may also be better stewards of their own health. A lifestyle designed to stave off migraines would include regular exercise, attention to diet and adequate sleep, all of which could boost overall health and cognitive function.

It will take more targeted studies to untangle all of these contributing factors, says Kalaydjian. When she factored information about sleeping habits, exercise and medication into analyses of her current data, the difference was still there, suggesting that these theories may not represent the whole answer.

It is also possible that migraines may genuinely deliver fundamental cognitive benefits in addition to these lifestyle factors, says Karen Waldie, a neuroscientist at the University of Auckland in New Zealand. Waldie speculates that decades of cerebral insult could train a migraineur's brain to better protect itself on a cellular level, and that sufferers' brains are "used to problems that the non-migraineur might not have experienced".

References : Kalaydjian A., Zandi P. P., Swartz K. L., Eaton W.W. & Lyketsos C. Neurology, 68. 1417 - 1424 (2007).

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http://www.futura-sciences.com/news-migraines-ameliorent-elles-memoire_10728.php
Par Jean Etienne, Futura-Sciences, le 26/04/2007 à 11h03

C'est ce qu'on pourrait penser, si l'on en croit les résultats obtenus par une équipe de scientifiques américains, en se basant sur des tests passés auprès de sujets migraineux à partir de 1993, et dont les résultats ne manquent pas de surprendre.

Amanda Kalaydjian et ses collègues de l'Ecole de Santé Publique Johns Hopkins Bloomberg, à Baltimore, a évalué sur le long terme l'évolution des facultés de mémorisation, entre autres, de 1448 femmes volontaires, membres de la Baltimore Epidemiologic Catchment Area Study. Parmi elles, 204 migraineuses chroniques.

Deux séries de tests ont été pratiquées, d'abord entre 1993 et 1996, puis entre 2004 et 2005. Ceux-ci consistaient essentiellement en des exercices de mémorisation, ce que l'on appelle communément un "Mini-Mental State Examination".

Sans surprise, les chercheurs ont d'abord constaté que les femmes migraineuses obtenaient de moins bons scores en comparaison aux sujets ne souffrant pas de cette affection. Mais la mise en corrélation des résultats des deux séries de tests a surpris toute l'équipe, car il apparaissait nettement que si les facultés cognitives diminuent avec l'âge, celles des migraineuses se réduisent nettement moins vite.

Comment expliquer ces résultats ? A cette question, Amanda Kalaydjian ne peut qu'émettre des hypothèses. Même si les causes de la migraine paraissent essentiellement liées à des anomalies vasculaires entraînant vasodilatation et augmentation de la perméabilité vasculaire, elles restent incomplètement élucidées, et difficiles à identifier. Actuellement, les chercheurs ignorent par quel mécanisme cette pathologie pourrait freiner la perte de facultés liée au vieillissement.

L'équipe ne pense pas que cet effet bénéfique soit lié à la prise de médicaments anti-inflammatoires. Cependant, elle n'exclut pas que le mode de vie des migraineux, rendu plus sain par suite de périodes de repos plus longues, de séances de relaxation anti-stress, et surtout de la volonté de réduire la consommation d'alcool, source de déclenchement de cette pathologie, pourrait expliquer en partie ces résultats.

Mais Amanda Kalaydjian estime qu'il existe vraisemblablement un facteur biologique à la base de cette différence, basé sur l'activité neuronale et la vasodilatation, qui jouerait un rôle de protection chez les migraineux.