NEW YORK (Reuters Health) - It's been clear for some time that psychological stress is linked to high blood pressure, or hypertension, but the reason is unknown.

And until recently, investigations of a stress-hypertension link have been conducted in laboratories, using staged activities such as public speaking and mental arithmetic to ''stress out'' participants.

Now, in a ``real-world'' setting, a research team in Italy has confirmed that mild stress can increase blood pressure and impair the cardiovascular system's ability to regulate itself.

``These changes...might contribute, in susceptible individuals, to the link between psychological stress and increased cardiovascular risk of hypertension,'' the team suggests in the January issue of Hypertension: Journal of the American Heart Association.

The scientists detected the changes using a technique called autonomic assessment, which measures alterations in the autonomic nervous system, senior researcher Dr. Massimo Pagani told Reuters Health. The autonomic nervous system controls blood pressure, the heart's rhythm and its ability to contract, and other important bodily functions.

Changes in autonomic function can be detected by ''computerized analysis of beat-by-beat cardiovascular variability'' on an electrocardiogram, Pagani explained.

Pagani, an internal medicine specialist at the University of Milan, and colleagues used electrocardiography and blood pressure measurements to evaluate 30 medical students on two occasions: 30 to 60 minutes before they took an examination and again 3 months later while they were on break from classes.

They confirmed that the students were indeed stressed on the exam day, based on their responses to psychological questionnaires, their saliva levels of the stress hormone cortisol, and their saliva levels of cytokines, proteins the immune system releases when the body is stressed.

The students' blood pressure and heart rate were markedly higher on the exam day than on the vacation day, the researchers determined. Other autonomic measures, such as heart rate variability, a measure of the heart's ability to handle stress, were also elevated on exam day.

``Our goal was to find a technique to assess the stress level acting in any patient,'' Pagani told Reuters Health, so that eventually therapy for high blood pressure can be ''individually planned with tailored lifestyle changes.'' In some cases, these would include non-drug therapies such as ''exercise, food reprogramming and relaxation,'' he said.

In other cases, medication would be needed, and autonomic assessment of patients could help physicians choose the drug, Pagani added.

For example, he pointed out, beta-blockers and ACE inhibitors inhibit an important component of the autonomic nervous system, called the sympathetic nervous system. Conversely, calcium-channel blockers, a different class of antihypertensive drugs, boost the sympathetic nervous system. Autonomic assessment could make it clear whether a patient's sympathetic nervous system is adequate or needs to be enhanced or suppressed.

``The main message,'' Pagani said, ``is that autonomic research might help empower patients, who will be progressively in charge of their own well-being, and fight against cardiovascular risk.''

SOURCE: Hypertension 2002;139:184-188.

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