Migraines during pregnancy linked to stroke and vascular diseases: US population based case-control study
BMJ 2009; 338 doi: https://doi.org/10.1136/bmj.b664 (Published 11 March 2009) Cite this as: BMJ 2009;338:b664
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This study of pregnancy-related migraines draws attention to the
consequences of disregarding published information in the field of blood
rheology. Unfortunately the science of haemorehology has failed to gain
clinical recognition, but this does not alter the fact that increased
blood viscosity is an important pathological factor in many chronic
disorders. An example of this lack of recognition is the statement,
"Women with peripartum migraines were also more likely to have vascular
risk factors such as diabetes,hypertension and tobacco smoking, etc"
without apparent recognition that all three factors are associated with
increased blood viscosity. The statement, "We found that women with pre-
eclampsia were twice as likely to have peripartum migraine as those
without pre-eclampsia," shows a lack of awareness of those published
studies which link pre-eclampsia with increased blood viscosity.
Several studies from workers in European countries have used SPECT to
show focal hypoperfusion during pain-free periods, with more widespread
hypoperfusion during attacks. A Danish study noted, "The first observable
event was a decrease of regional cerebral blood flow, posteriorly in one
cerebral hemisphere. Further development of this pathological process was
accompanied by aura symptoms. Thereafter headache occurred while cerebral
blood flow remained decreased." An Italian group noted that migraineurs
had significantly reduced red cell filterability index and significant
increases in low shear rate blood and plasma viscosity. Such changes
could contribute to the reduced blood flow rate reported by the Danish
group.
The role of diet in migraine has been investigated by several groups
and they draw attention to the adverse effects of chocolate, cheese,
citrus fruits, milk nuts and cola drinks. One study concluded, "Our
study suggests that foods may trigger not only migraine, but also tension
type headache attacks." An adverse response to a food will alter the
internal environment sufficiently to cause an increase in blood viscosity
and reduce red cell deformability.
As impaired cerebral blood flow is associated with cognitive problems
in other disorders, the results of a Spanish study are relevant. Areas of
brain hypoperfusion were found in patients with poor results from tests of
verbal or visual memory. A SPECT study reported from a group in Turkey
noted that, "The SPECT images revealed clear interhemispheric asymmetry in
the upper frontal and occipital parts of the brain in migraineurs. It is
suggested that an impaired regional cerebral autoregulation may exist even
during headache-free intervals in patients suffering from migraine."
Thus there are good reasons to conclude that migraines are associated
with both increased blood viscosity and poorly deformable red cells, and
that such changes are manifested as impaired blood flow. This conclusion
seems to imply that migraine occurs only in genetically predisposed
individuals. Therefore, when exposed to other conditions with increased
blood viscosity, the effects would be cumulative. For example, there are
many reports which show that smoking is associated with increased blood
viscosity and poorly deformable red cells. So it is not surprising that
the NCPP study noted that pregnant migraineurs who smoked had a higher
prevalence of heart disease than non-smoking pregnant migraineurs.
It was stated, "We found that women with pre-eclampsia were twice as
likely to have peripartum migraines as those without pre-eclampsia." But
there are several reports which record that pre-eclampsia is associated
with increased blood viscosity. For example, Hobbs et al (1) reported in
1982 that blood viscosity was increased in patients with pre-eclampsia.
The English translation of the abstract of a Japanese study stated, "In
severe pre-eclampsia subjects, viscosity was significantly higher than in
normal pregnancy cases. The natural decrease in peripheral blood flow
resulting from elevated viscosity threatens the lives of both mother and
foetus." Similar findings have been reported by others.
A significant literature documents the roles of blood viscosity and
poorly deformable red cells in cardiovascular and cerebrovascular
disorders and that literature has been summarised. (2)
It is concluded that the importance of recognising the role of blood
viscosity in chronic disorders is that it draws attention to potentially
helpful treatments. For example, Bic et al (3) found that a low-fat diet,
similar to the Swank low-fat diet for multiple sclerosis, had a beneficial
effect on migraine headaches. It was stated, "The decreased dietary fat
intervention was associated with statistically significant decreases in
headache frequency, duration and medication intake (all p<0.0001)."
Later it was stated, "There was a significant positive correlation between
baseline dietary fat intake and headache frequency
(r=.44, p=0.02)" It is likely that the reduced fat intake would be
associated with lower blood viscosity. Gibson (4) stated, "There appears
to be sufficient evidence to suggest that patients at risk from heart
disease could
benefit from a low dose (1 to 6 g/day) of fish oil in conjunction with a
prudent diet." Such a regimen could be beneficial for migraineurs.
It is concluded that studies involving chronic disorders which do not
take cognisance of the haemorheological situation may draw conclusions
which have little relevance to sufferers and their medical advisors.
References.
1. Hobbs JB, Oats JN, Palmer AA, et al. Whole blood viscosity in
preeclampsia. Am J Obstet Gynecol 1982;142:288-92.
2. Simpson LO. Blood viscosity factors - the missing dimension in modern
medicine. The Mumford Institute, Highlands, New Jersey, 2008.
3. Bic Z, Blix GG, Hopp HP, et al. The influence of a low- fat diet on
incidence and severity of migraine headaches.
J Womens Health Gender Based Med 1999;8:623-30.
4. Gibson RA. The effects of diets containing fish and fish oils on
disease risk factors in humans. Aust NZ J Med 1988;18: 713-22.
Competing interests:
None declared
Competing interests: No competing interests
The large amount of data and the statistical analyses in this paper
look impressive and unfortunately may fool many readers into believing the
conclusions made by the authors. The authors do acknowledge that the
discharge diagnostic codes miss many patients who suffer from migraine
headaches. This diagnosis is not only missed upon discharge, but it is an
established fact that migraine is significantly underdiagnosed by the
majority of primary care doctors. Obstetricians are not likely to do a
better job in distinguishing sinus and tension-type headaches from
migraines, or diagnosing a migraine aura, particularly when managing a
pregnant woman in the hospital. It is true that migraines improve in
pregnancy, but considering that about 18% of women suffer from migraine
headaches, it is hard to believe that only one in 100 of these women will
continue having migraines during pregnancy. Obviously, when a
complication, such as stroke occurs the diagnosis of migraine is much more
likely to be recorded than when no complications occur.
The authors provide many disclaimers and state that "On the basis of the
select group of pregnant women with migraines coded during the hospital
admission, this may not represent the population of women with migraine as
a whole". Nevertheless, they go on to present and analyze this highly
inaccurate data and even draw conclusions. It is very unfortunate that
the publicity associated with this paper (I first saw it reported on
Yahoo.com) will cause unnecessary anxiety to millions of pregnant women.
Competing interests:
None declared
Competing interests: No competing interests
This interesting study confirmed that people who suffer from migraine
may have a slightly greater risk of stroke. Migraines during pregnancy
were linked to a 15-fold increased risk of stroke. Migraines also tripled
the risk of blood clots in the veins and doubled the risk of heart
disease. Vascular risk factors were also strongly associated with
migraines. These included diabetes, high blood pressure and cigarette
smoking.
However, stroke is generally caused by a number of factors working in
combination. The higher risk for stroke may be related to reduced blood
flow in the brain during a migraine, but the exact mechanism for this
association is unknown. A theory suggest that strokes can occur as the
result of a syndrome called "reversible cerebral vaso-constriction
syndrome" (RCV). Other factors which can increase the risk of stroke
include the use of oral contraceptives and cigarette smoking should be
concerned. A young woman who experiences frequent migraine should minimize
the risk of stroke by quitting cigarettes and using other forms of birth
control.Lifestyle modification should be done in people with classic
migraine. They should stop smoking, eat fruit and vegetables and have
high blood pressure control
Competing interests:
None declared
Competing interests: No competing interests
Re: Deeply flawed data
As the first author of this paper I would like to respond to the
criticisms brought forth by Dr. Mauskop. We clearly stated in the
abstract and the body of the paper that our conclusions only represent
women with active migraines during hospitalization. These results should
not be extrapolated to all women with migraines or those who have been
misdiagnosed or the diagnosis was not recognized. Therefore we are not
presenting "inaccurate" data--the data are what they are. We were very
careful to try to dispel alarm, as well, especially with the BMJ press
release. How other news services, such as Yahoo, represent our data is
beyond our control, and they did not interview me or my coauthors
directly. Lastly, to reiterate our points, the following is the main
point of our conclusions:
"To summarise, we identified a coexistence of diagnoses of peripartum
migraine with vascular diseases and vascular risk factors during pregnancy
in a subpopulation of women with active migraine during admission to
hospital. Obstetricians, general practitioners, and neurologists should
all realise that these results do not apply to every woman with migraine
during pregnancy. However, for pregnant women admitted to hospital with
active migraines , modifiable cardiovascular risk factors and
complications of pregnancy such as pre-eclampsia, should be recognised and
treated."
Competing interests:
None declared
Competing interests: No competing interests