• Researchers investigated the link between high blood pressure and epilepsy.
• They found that high blood pressure increases the risk of epilepsy by around 2.5 times but taking antihypertensive medications reduces this risk.
• They conclude that while high blood pressure is a risk factor for epilepsy, further research is needed to understand the underlying mechanisms of the link.

Epilepsy is the third most common neurological condition that affects older people after stroke and dementia.

Research shows that late-onset epilepsy has become more widespread in the last 2 decades. The number of people with the condition will probably continue to rise as the aging population increases, and epilepsy will likely become a significant public health concern.

Despite this, the underlying causes of epilepsy in 32–48% of cases remain unclear. Some research suggests that vascular risk factors may increase the risk of late-onset epilepsy. Other research indicates that vascular risk factors may be involved in epilepsy, beginning in a person’s 30s.

Understanding the role of vascular risk factors in late-onset epilepsy could help policymakers design public health measures and preventive strategies to curb and manage rates of the condition.

Recently, researchers led by the Boston University School of Medicine in the United States conducted a study investigating the link between vascular risk factors and the onset of epilepsy.

They found that hypertension had links to an almost 2-fold higher risk of developing late-onset epilepsy. This risk was even higher for those who did not use medication to regulate their blood pressure.

The study appears in Epilepsia.

Data analysis

The researchers used data from the Framingham Heart Study (FHS), an ongoing, community-based study that began in 1948. Its Offspring Cohort tracks the health outcomes of 5,124 of the original participants’ children from health examinations every 4 years.

Altogether, the researchers used data from 2,986 people who attended their fifth examination between 1991 and 1995, were at least 45 years old during the period, and whose health records contained data on vascular risk factors.

The vascular risk factors collected included systolic and diastolic blood pressure. The researchers characterized high blood pressure as systolic blood pressure of 140 millimeters of mercury (mm Hg) and above, and diastolic blood pressure of 90 mm Hg and above, as well as the use of antihypertensive medications.

The researchers also screened for:

• diabetes
• cholesterol levels
• smoking status
• cardiovascular disease
• stroke
• body mass index (BMI)

To screen participants for epilepsy or seizure, the researchers used routine chart reviews for neurological conditions, self-reported seizures, International Classification of Diseases Ninth Revision (ICD-9) codes linked to epilepsy or seizures, and antiepileptic drug use.

The researchers also used brain imaging and electroencephalography (EEG), cardiac and other relevant data to ascertain cases of epilepsy.

Among the cohort, the research identified 55 examples of epilepsy, of which 26 were definite, 15 probable, and 14 suspected. Individuals were an average of 73.8 years old at the time of potential diagnosis.

The researchers found that hypertension had links to an almost 2-fold higher risk of epilepsy. However, the other risk factors had no links to epilepsy.

After excluding people taking antihypertensive medications, the researchers noted that high blood pressure had links to a 2.44-fold high risk of developing epilepsy.

They also found that every 10 mm Hg change in systolic blood pressure was associated with a 17% higher risk of developing epilepsy.

Underlying mechanisms

Several theories may explain the link between epilepsy and hypertension. One mechanism may be via the renin-angiotensin system (RAS), which regulates blood pressure.

Research suggests that after repetitive seizures, rats have 2.6–8.2 times the components of RAS than mice without seizures. Antihypertensive drugs that lowered levels of RAS components delayed seizure onset and reduced seizure frequency.

However, more research is needed to understand how much this mechanism explains the link between epilepsy and hypertension, as other research suggests the system may have a limited effect.

According to the researchers, another possible underlying mechanism is small vessel disease (SVD), a condition in which the walls of small arteries and capillaries are damaged and thus do not deliver sufficient oxygen-rich blood to various organs. In a recent study, scientists found that the duration of high blood pressure is a strong predictor of SVD in later life.

The researchers add that SVD has links to temporal lobe epilepsy. Possible mechanisms include cortical microinfarcts, small lesions in cortical tissue, and the disruption of U fibers that may lead to excessive excitability and thus seizures. U fibers connect neighboring areas of the cerebral cortex.

The researchers conclude that hypertension is an independent predictor of late-onset epilepsy and carries a 2-fold risk of developing seizures after 45 years.

They note, however, that there are limitations to their study. As it primarily included white participants, it may not represent all ethnicities and races. The researchers also say that its nature as an observational study means that it cannot prove causality.

“These results are particularly interesting because whether or not high blood pressure (hypertension) in and of itself is an independent risk factor for stroke has been a topic of controversy,” Dr. Jason Hauptman, a neurosurgeon at Seattle Children’s Hospital told Medical News Today. “The thought is that independent of the presence of stroke, hypertension may lead to disease of small arteries throughout the brain that can cause injuries on the microscopic level.”

“These injuries could potentially lead to epilepsy with or without the presence of a visible or symptomatic stroke. This research is important because hypertension is not only common, but it is modifiable – that is, we may have ways of assessing and treating it. This would need to be pursued in larger, more diverse patient populations to fully assess exactly how much this is a risk factor and to test the potential interventions,” he added.

When asked whether these results were surprising, Sanjay Prasad, M.D., a cardiologist at Mayo Clinic Healthcare in London, who was not involved in the study, told MNT that they are not surprising and match previous findings.

“This work is observational, so does not confirm that there is a definite direct link. However, it builds on our knowledge base and highlights the importance of lifestyle, regular exercise, and a low salt intake to control blood pressure as an important way of reducing morbidity,” he added.

“[These results highlight] the need for aggressive control of blood pressure — and encourage everyone —particularly those above the age of 50, to regularly monitor their blood pressure. We also need to assess the impact of blood pressure control in those with epilepsy and after a stroke.”

– Dr. Prasad

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