Blood pressure and headaches: is there a connection? (Part I)

The question of how headaches and high blood pressure relate to each other has frequently been examined in medical research. However, to this day, the results in this field are inconsistent and continue to give rise to debate among specialists. Particularly where it is assumed that headaches and high blood pressure are occurring simultaneously, there is no evidence in most cases that both could also be causally related. This is because no control process in the body that could be responsible for this has yet been found. This is why we must remember that we cannot necessarily infer that one thing causes the other based on an apparent connection. Therefore, the simultaneous occurrence of high blood pressure and headaches does not necessarily mean that there is a causal link. The purpose of this paper is to highlight some of the results of current research and to provide an outlook on the most exciting questions for future development in the field.

“Comorbidity” – when illnesses are (apparently) connected: what do we know in this case?

Various studies in the context of more recent research describe this kind of “coincidence” between headaches and high blood pressure. This means, they state that headaches and high blood pressure occur together in patients. Depending on how the study is designed, the composition or size of the group of affected people being examined, and the particular type of headache, the results of the sometimes rather extensive studies vary. Therefore, different surveys reach different conclusions regarding for example, how high the percentage is of those who are “doubly affected”, as it were, who suffer from high blood pressure as well as headaches – and vice versa.

Who affects whom: from high blood pressure to headache or vice versa?

Turning our attention to migraine, we can see how different studies are trying to map the connection between headache symptoms and high blood pressure in different ways. One study in Finland medically monitored people with migraine over a period of five years, while recording different health parameters. After this period, they found that people with migraine had a demonstrably higher risk of developing high blood pressure than was the case in the control group without migraine. However, it must be noted here that the migraine diagnosis was declared by the participants themselves and not medically verified.

In the Finnish study, researchers were therefore asking whether people with migraine experience high blood pressure more frequently than the healthy population. To a certain extent, a New York study did the opposite; here, they discovered that out of the 1,300 observed participants – who had an average age of 68 – 76% had high blood pressure. Again, there was a significantly higher rate of migraine with and without aura in this group. The joint occurrence of both illnesses was especially pronounced when the high blood pressure was untreated or had persisted over a longer period (longer than 9 years).

Causes are unclear

These kinds of research approaches provide an indication of whether and to what extent certain headache disorders occur together with high blood pressure for affected people. However, we hardly know anything about the exact connection between headache symptoms and high blood pressure, i.e., the exact backgrounds of this coincidence. Could there be common causes for both illnesses? Does the trail lead to blood vessel damage?

An Italian-French paper from 2013 provides an approach to potential pathways through which high blood pressure can develop, especially for people with migraine, and which factors could contribute to this. It reports that there are often pathological changes to the blood vessels of migraine patients. Consequently, there is a hardening/stiffening of the vascular walls, which impairs their flexibility. This makes important regulatory processes (e.g., tightening or widening the vessels), with which the body sets and adjusts the blood pressure (key word: disturbed balance), more difficult. Moreover, the vessel tissue, or more precisely, the layer of cells which lines the inside of the vessels, the so-called “endothelium”, becomes damaged. This can also negatively affect elasticity and mobility as well as the blood vessels’ response to regulatory messenger substances. The author reports that, in addition, the findings are similar with regard to the large arteries in the body: regulatory processes here are also impaired for people with migraine.

Further evidence: the blood vessels in the brains of people with migraine

A Polish investigation from 2015 confirms the theory of the impaired vascular endothelium for people with migraine; the authors find functional impairment of the blood vessels in the brain and damaged tissue. They point out that the risk of stroke is also higher with migraine. Furthermore, they discover – presumably as a result of vessel damage – brain areas with a low blood supply with so-called ischaemic lesions. This is damage which is caused by an insufficient supply of blood and therefore of oxygen. This paper also points out that changes to the blood-brain barrier can occur in the context of the wavelike excitation propagation during a migraine attack. This can also result in an insufficient blood supply, further worsening the impairment due to the migraine attack.

However, whether the pathological changes described above are limited to the area of the head or whether the whole body is affected (particularly keeping in mind the blood vessels), has not yet been conclusively resolved. There is still a great deal of research to be done here.

The next part of our two-part series on blood pressure and headaches will appear next month. There, we will take a look at the connection between high blood pressure and altered pain perception, consider the evolutionary purpose, and take a look at the future of research.

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