Establishing a link between heart rate and pain in healthy subjects: a gender effect.

Heart rate (HR) is currently used by rehabilitation clinicians as a complementary objective measure of pain. The premise is that, as pain increases, HR should also increase. However, this relationship is not clearly established. The goal of this study was to verify the relationship between HR and pain perception. Thirty-nine healthy volunteers participated in this experimental study. Painful stimuli were induced by a 2-minute immersion of the hand in hot water (47 degrees C). HR was recorded before and during the stimulation and was matched to a pain rating. We observed a rise of 11% in HR after 2 minutes of immersion. There was a significant intrasubject correlation between HR and pain intensity (r = 0.50, P < .001) and pain unpleasantness (r = 0.55, P < .001). Furthermore, there was a strong gender effect in the intersubject correlations. Men presented a strong correlation between mean HR and mean pain perception (intensity: r = 0.77, unpleasantness: r = 0.86), whereas this relationship was absent in women (intensity: r = -0.2, unpleasantness: r = 0.001). In conclusion, results show that, for healthy volunteers, experimental pain can elicit a rise in HR up to 11%. Moreover, the relationship between HR response and pain is gender related. Considering that a positive relationship between HR and pain perception was only found in men, these results do not support a clinical significance of the use of HR for pain evaluation in women. Clinical implications need to be further evaluated with patients before clinicians can use HR as a complementary tool in pain assessment. PERSPECTIVE: A positive correlation between HR and pain was observed for men but not for women. These differences underline the importance of taking into account gender differences in the development of complementary pain assessment. Further research should be conducted to verify the role of sex hormones on heart rate and pain.