A persistent rumour postulates that donating blood may alleviate migraine symptoms. A major study now finds no evidence to support this hypothesis. A researcher says that there may be a short-term effect, but this is not enough to warrant further investigation.
Migraine can be extremely debilitating, and many people will do anything to eliminate the headache.
Some people use painkillers, triptans or the newest drugs on the market such as monoclonal antibodies or gepants (small-molecule CGRP receptor antagonists).
Others pursue alternative therapy, and many people for centuries assumed that pressure causes migraine and have therefore considered drawing blood to reduce this pressure.
Many scientific arguments may be made for drawing blood to relieve migraine, but researchers found no evidence that this works in a major new study.
Having migraine was not associated with changes in blood donation, nor was blood donation associated with reducing the prevalence of migraine.
“We do not think that further investigation would be useful. If we had seen a signal, there might have been something to follow up on, but our study did not find any link between donating blood and having fewer migraine symptoms,” explains a researcher behind the study, Thomas Folkmann Hansen, Associate Professor, Danish Headache Center, Rigshospitalet, Copenhagen, Denmark.
The research has been published in Transfusion.
Plausible idea
The idea that donating blood could reduce migraine symptoms is plausible.
Thomas Folkmann Hansen says that in the preliminary studies leading up to the main study, the researchers asked both people with migraine and personnel at blood donation clinics about the hypothesis, and it was well known.
The personnel said that some people donate blood because they have migraine, and some people with migraine said they were certain that their doctor had recommended it.
Imagining a mechanism by which donating blood might reduce the migraine symptoms is easy. For example, drawing blood could reduce pressure in the blood vessels, including in the brain, and thereby relieve migraine pain.
According to Thomas Folkmann Hansen, various molecules in the blood could be involved in migraine attacks, and donating blood would dilute the concentration of these molecules in the blood by replacing this blood with primarily water.
“Many scientific arguments can be advanced that donating blood could reduce the degree of migraine. Investigating something that had not previously been investigated was therefore interesting,” he says.
Data on more than 1 million people
The researchers examined the links between migraine and blood donation in two large population cohorts.
One cohort included data on more than 1 million blood donors in Denmark in the Scandinavian Donations and Transfusions Database. The researchers investigated differences in blood donation between people treated with triptans for migraine and people from the background population.
The second cohort was from the Danish Blood Donor Study, and researchers had specifically asked 60,000 people in Denmark about their health, including whether they had migraine.
The researchers investigated both whether behaviour differed between blood donors with and without migraine and whether any evidence indicated that blood donors have fewer migraine attacks.
“If donating blood really reduces migraine, we would expect people with migraine to change their blood donation behaviour,” explains Thomas Folkmann Hansen.
Blood donation not associated with behaviour change
The results clearly show that people who thought that blood donation could reduce migraine pain should reconsider.
The researchers did not find that blood donors had fewer cases of migraine, nor were there more blood donors among people with migraine.
How frequently people with migraine donated blood did not differ either. In fact, people with migraine more often stopped donating blood.
The interval between donations was also slightly longer for people with migraine.
The researchers only examined data from people with a genetic predisposition to migraine, but not migraine diagnoses or treatment with triptans, and found no difference between people with a genetic predisposition and the background population.
Based on the results, the researchers conclude that the evidence does not support the idea of using blood donation to alleviate migraine symptoms.
“We conclude that there is no reason to investigate this subject further. We had expected that if donating blood actually affected migraine, we would see change in blood donation behaviour, but we did not find evidence of this,” says Thomas Folkmann Hansen.
Possible minor effect does not change behaviour
Thomas Folkmann Hansen will not completely reject that some people with migraine can benefit from blood donation, but the effect will be very brief in these cases.
Drawing blood could change the pressure or the concentration of molecules in the blood relevant to migraine, but any relief would not last long.
The body replaces blood loss rapidly. Blood pressure hardly changes, and the concentration of various molecules in the blood normalises within a few weeks.
If blood donation had a short-term effect, then donating quite often would be required, which does not make sense and is unrealistic.
“And then even if there is an effect, it is not large enough for people with migraine to change their blood donation behaviour. If they experienced less migraine after each blood donation, even if it only lasted briefly, we would expect people with migraine to donate blood more often than the background population, but we found the opposite,” concludes Thomas Folkmann Hansen.
