The influence of resting blood pressure and gender on pain responses.

Recent research suggests that resting blood pressure is inversely related to pain sensitivity, even among normotensives; however, most of these studies have included only male participants. To determine whether this hypoalgesic effect of blood pressure was also present in females, we investigated thermal and ischemic pain responses in a group of age-matched, normotensive females and males as a function of resting blood pressure. Thermal pain threshold and tolerance were determined, and a cross-modality thermal magnitude matching procedure was conducted, after which ischemic pain threshold and tolerance were determined using the submaximal effort tourniquet procedure. Systolic pressure, diastolic pressure, and heart rate were obtained using an automated blood pressure monitor with a pneumatic cuff positioned around the left ankle. Females provided higher normalized thermal magnitude estimates and a shorter time to ischemic pain tolerance, but no gender differences emerged on other pain measures. Systolic, diastolic, and mean arterial pressures were significantly correlated with thermal and ischemic pain responses among males but not females, with higher blood pressure being associated with lower pain sensitivity. After adjusting for resting blood pressure, the gender difference in normalized magnitude estimates was only marginally significant, and the gender difference in ischemic pain tolerance became nonsignificant. These findings are consistent with previous research indicating an inverse relationship between blood pressure and pain sensitivity. Additionally, the findings also suggest that blood pressure may partially moderate gender differences in pain sensitivity. Potential mechanisms and clinical implications of the current findings are discussed.