Anxious individuals tend to have heightened blood pressure and sympathetic nerve activity, according to new research published in the American Journal of Physiology. The findings provide evidence of an important relationship between anxiety and autonomic blood pressure regulation.
“Anxiety is unfortunately growing more and more prevalent, and COVID-19 really cast a light on the epidemic,” said study author Jason R. Carter, a dean and professor at the Robbins College of Health and Human Sciences at Baylor University.
“Our lab was interested in looking at the relationship between anxiety and the sympathetic nervous system in otherwise healthy adults because there was not only a scientific gap in this area, but also because it can take years for anxiety to manifest into cardiovascular disease. The techniques we use to assess the sympathetic nervous system is highly specialized, and can provide unique insights into underlying physiological mechanisms that can ultimately contribute to cardiovascular disease when there is dysfunction.”
The study involved healthy adults between the ages of 18 and 47 with a body mass index (BMI) below 35 kg/m2 who were non-smokers and had no known diabetes, cardiovascular or autonomic disorders, and were not taking any medications. Female participants were premenopausal and had regular menstrual cycles. A total of 88 participants (52 males, 36 females) were included in the final analyses.
The participants completed a widely-used assessment of anxiety known as the Spielberger State/Trait Anxiety Inventory before completing tests of autonomic function. For the current study, the researchers focused on trait anxiety, a stable personality characteristic that reflects a tendency to perceive a wide range of situations as threatening or dangerous, leading to increased feelings of worry, nervousness, and apprehension.
Unlike state anxiety, which is temporary and situation-specific, trait anxiety is a chronic predisposition that affects how individuals perceive and respond to different stressors across various contexts.
The autonomic testing involved resting blood pressure measurements, heart rate, beat-to-beat blood pressure, and muscle sympathetic nerve activity (MSNA). Three additional brachial blood pressure measurements were taken, and 10 minutes of quiet, resting autonomic and cardiovascular measurements were collected. Participants were required to fast for at least 3 hours and refrain from caffeine, alcohol, and exercise for at least 12 hours before autonomic testing.
The researchers found that trait anxiety was independently associated with both resting blood pressure and MSNA. This was true even after controlling for the effects of age and sex.
“The take home from this study is that both blood pressure and the sympathetic nervous system are associated with self-reported anxiety, and in a direction where higher blood pressure and sympathetic activity is more prevalent with higher anxiety,” Carter told PsyPost. “This was observed in otherwise healthy adults, as opposed to prior work that has focused on various clinical anxiety populations and/or populations with comorbid diseases. Bottom line – we all need to be concerned about anxiety, even when we seem healthy.”
This is the first time a relationship between anxiety and autonomic blood pressure regulation has been discovered in a large group of healthy individuals. “We were surprised no one had looked for this relationship in otherwise healthy adults before,” Carter remarked.
But the new study, like all research, includes some caveats.
“The study was not statistically powered to look for potential differences that might exist between male and female participants,” Carter explained. “We know that females tend to report higher levels of anxiety, and so the influence of biological sex will be important to address in future work.”
“While this work demonstrated a modest, yet significant, association – it is important to note that the study design did not allow a cause-and-effect conclusion. The relationships between anxiety, blood pressure, and the sympathetic nervous system are complex.”
“We have much more work to do using various and ethical experimental models before we can conclude that modifying anxiety would alter blood pressure and/or sympathetic nerve activity trajectories,” Carter added. “While there is other evidence to suggest this is very plausible, more work is needed.”
The study, “Blood pressure and muscle sympathetic nerve activity are associated with trait anxiety in humans“, was authored by Jeremy A. Bigalke, John J. Durocher, Ian M. Greenlund, Manda Keller-Ross, and Jason R. Carter.