Heart Rate Variations May Predict Reactions to Stress

Variations in heart rate can help identify individuals at the greatest risk for high stress levels, the results of a Canadian study suggest.

Previous research has identified respiratory sinus arrhythmia (RSA) as a potential indicator of how individuals emotionally react to stress. The current study, published in the September 2014 issue of Stress, analyzed whether variations in heart rate could predict future increases in stress among college students.

For the study, students completed a questionnaire about their psychological well-being, stress levels, and heart rate measures during a low-stress period at the beginning of the semester. RSA was measured when the students were told to relax, as well as when they were asked to concentrate on their biggest worries.

RSA was then gauged again during interviews in which students were asked to list and rate the likelihood and the intensity of potential consequences of those worries. The experiment was repeated during a high-stress period prior to exams.

The results indicated that RSA was significantly associated with stress levels. During the low-stress period, variations in heart rate significantly decreased when students focused on their worries, compared with their RSA levels during relaxation. Additionally, students who reported higher levels of psychological distress at baseline had greater decreases in heart rate variability while thinking about their stressors, compared with their less-stressed peers.

“At rest, a more variable heartbeat is a good thing. It shows that your parasympathetic nervous system is hard at work,” said lead study author Jean-Philippe Gouin, PhD, in a press release. “That’s the system that’s responsible for the ‘rest-and-digest’ state of being—the opposite of ‘fight-or-flight.’ The rest-and-digest phase puts you in a calm state that allows you to conserve and replenish your energy.”

Overall, stress levels significantly increased from the beginning of the semester to exam time. After adjusting for age, sex, and ethnicity, low RSA at rest and while thinking about worries predicted larger increases in physiological distress during the high-stress period. This relationship between low RSA during the low-stress period and increases in future stress levels remained significant after accounting for baseline stress levels.

As a result, resting RSA and its reactivity to stress could help identify those who are most susceptible to experiencing increases in psychological distress as a reaction to stress.

“By pinpointing those in the general population who are most vulnerable to stress, we can intervene before they hit the breaking point—and hopefully prevent the negative consequences of stress by doing so,” Dr. Gouin said. “That’s why it’s important to have an objective diagnostic tool like this one.”