Migraines may be extremely painful, but they may also lower women's risk of developing type 2 diabetes.
Although migraine and type 2 diabetes are both common conditions, data on a link between the two "are scarce," say the researchers.
They describe their findings in a paper that now features in the journal JAMA Neurology.
The women had filled in health and lifestyle questionnaires every few years between 1990 and 2014. These included questions about migraines.
Information on diagnosed type 2 diabetes came from the insurance scheme's drug reimbursement database.
The analysis revealed that women with active migraine had an approximate 30 percent decreased risk of developing type 2 diabetes compared with women with no history of migraine headaches.
The investigators defined active migraine as having experienced migraine in the period since the last survey.
Need to understand underlying mechanisms
First and corresponding author Dr. Guy Fagherazzi of the Institut National de la Santé et de la Recherche Médicale (INSERM) in France and colleagues call for further research to "focus on understanding the mechanisms involved in explaining these findings."
According to the Global Burden of Disease Study 2017, headache disorders (consisting mainly of migraine), are the second leading cause of disability worldwide. Diabetes is the fourth.
The World Health Organization (WHO) suggest that migraine affects "at least 1 in 7 adults" worldwide, with women nearly three times more likely to develop them than men.
While the condition mostly affects those in the 35-45 year age group, it can also affect others, including children.
In their discussion of the results, Dr. Fagherazzi and his colleagues speculate on what might underpin the link between migraine and type 2 diabetes.
One mechanism that they suggest is the activity of a molecule called calcitonin gene-related peptide (CGRP) that is common in the development of migraine and is also involved in glucose metabolism.
"It has been reported," they write, "that rats with experimentally induced diabetes have a decreased density of CGRP sensory nerve fibers."
Results confirm what doctors have observed
Headache specialists Dr. Amy A. Gelfand of the University of California, San Francisco, and Dr. Elizabeth Loder of Brigham and Women's Hospital, Boston, MA, comment on the study in an accompanying editorial.
They suggest that the findings, along with those of other migraine studies, make them wonder "what is migraine good for?"
Doctors in headache clinics have noticed for some time that few of people that they treat have type 2 diabetes.
Could this be because those with type 2 diabetes are "so busy managing" the condition that they do not notice their headaches?
Or are diabetes doctors also treating headaches and thus obviating any need for specialist headache care?
Or could it be, ask Drs. Gelfand and Loder, that "there is something about diabetes that suppresses or reduces migraine?"
They conclude that the recent research does shed some light on these questions.
However, as this was an observational study, it cannot say whether migraine causes reduced risk of type 2 diabetes. Neither can it say whether factors that raise or reduce risk of type 2 diabetes also reduce or raise migraines.
Therefore, the "reason for the inverse association" between migraine and type 2 diabetes remains "uncertain."
"These findings are in line with observations from clinical practice."
Drs. Amy A. Gelfand and Elizabeth Loder