Evidence from both hypertensive and normotensive individuals indicate that elevated blood pressure is associated with decreased pain sensitivity. The current study sought to experimentally raise blood pressure using 250 mg caffeine, and investigate its effects on the cold pressor pain experiences of 25 men and 25 women. In a placebo-controlled repeated-measures experiment, caffeine increased systolic and diastolic blood pressure, as well as producing more clearheaded and energetic feelings. Caffeine produced higher pain threshold and pain tolerance levels compared to placebo, and women had a lower tolerance to pain than men. Finally, a significant association was found between caffeine-related increase in systolic blood pressure and caffeine-related increase in pain tolerance. Furthermore, this association was the strongest in women. These results are discussed in light of future directions for pain and hypertension research.

For almost two decades, researchers have demonstrated that hypertension is reliably associated with decreased perception of pain. More recently, a growing body of evidence has begun to suggest that hypoalgesia is not a consequence of high blood pressure, as the phenomenon precedes the onset of hypertension in individuals at risk for the disorder. This article provides a review of empirical evidence of decreased pain perception in normotensive persons with a family history of hypertension, elevated resting blood pressure, or exaggerated cardiovascular reactivity to stress. Based on the existing evidence, hypoalgesia is argued to be a correlate of dysregulation of central nervous system structures involved in both pain control and cardiovascular regulation in individuals who are genetically predisposed to develop high blood pressure. As such, hypoalgesia may serve as a valuable method of identifying individuals at greatest risk for hypertension.