Date:

May 3, 2018

Source:

American Physiological
Society

Summary:

Sympathetic nerve activity to skeletal
muscle blood vessels — a function of the nervous system that helps regulate
blood pressure — increases during physiological and mental stress in people
with chronic anxiety, a new study finds. Over time, this response may increase
the risk of high blood pressure and heart disease, although the study did not
test this specifically.

Sympathetic nerve
activity to skeletal muscle blood vessels — a function of the nervous system
that helps regulate blood pressure — increases during physiological and mental
stress in people with chronic anxiety, a new study finds. Over time, this
response may increase the risk of high blood pressure and heart disease,
although the study did not test this specifically. The study, published ahead
of print in the Journal of Neurophysiology, was chosen as an APSselect
article for May.

Researchers from the
University of Iowa studied the responses of two groups of volunteers after they
experienced physiological and mental stressors. One group of people had chronic
anxiety as determined by standardized scales used to measure anxiety and depression.
The control group did not have anxiety. The research team placed the
volunteers’ hands in an ice-water bath for two minutes to assess their
responses to physiological stress. After a brief recovery period, the
participants verbally solved simple math problems as fast as they could for
four minutes to induce mental stress. Before the start of each test, the
researchers gave the participants a two-minute “warning” countdown.

The research team
inserted a tiny microelectrode into a nerve near the back of the participants’
knee to measure sympathetic nerve activity throughout testing. They monitored
the volunteers’ rate of blood flow and blood pressure in the upper arm and
heart rate via a finger cuff during both activities. Blood samples showed that the
anxiety group had higher levels of norepinephrine, a hormone that sympathetic
nerve fibers release in response to stress, before testing began.
Norepinephrine causes the blood vessels to contract, which raises blood
pressure.

The researchers observed
increased nerve responses in both groups before and during the ice bath and
math activities. However, the increase “was significantly greater among
[the anxiety group] compared with [the control group], suggesting an enhanced
sympathetic anticipatory response,” the research team wrote.

Heart rate increased
during the two-minute countdown, another sign that the anticipation of
impending stress or discomfort caused physiological changes in the body.
However, there was no significant difference between the anxiety and control
groups. “Future studies are warranted to determine whether augmented
[sympathetic nerve activity] is associated with deleterious end-organ
consequences in persons with anxiety and cardiovascular disease or
cardiovascular disease risk factors,” the researchers wrote.