Gender Differences in Blood Pressure-Related Hypoalgesia in a General Population: The Tromso Study

An inverse association between resting blood pressure (BP) and acute pain sensitivity is well documented. Whether BP-related hypoalgesia differs by gender is unclear from prior work. Whether it increases proportionally with BP throughout the full BP range is also unknown. We examined BP-related hypoalgesia in a general population sample (n = 10,371, aged 30-87) of equal gender distribution reflecting the extremely low through hypertensive BP range. Resting BP was assessed and individuals participated in a standardized cold pressor test, providing pain ratings every 9 seconds. For systolic BP (SBP), a significant SBP x Gender interaction was observed on mean pain ratings (P < .001). Females displayed significant BP-related hypoalgesia (P < .001), with males showing a 38% smaller effect (P < .001). A similar DBP x Gender interaction was also observed (P < .05). Spline regression indicated a significant (P < .001) change in slope of the SBP pain association at 140 mmHg. Among individuals with lower resting SBP (<140/90), increasing hypoalgesia with increasing SBP levels was observed (P < .001), with no further increases in those with higher BP (>= 140190; P > .10). This is the first large-scale study to confirm past results suggesting that BP-related hypoalgesia differs by gender; that is, females exhibited greater hypoalgesia. BP-related hypoalgesia appears subject to ceiling effects in the hypertensive BP range. Perspective: Females show greater BP-related hypoalgesia than males, highlighting gender differences in endogenous antinociceptive systems. Extent of BP-related hypoalgesia does not increase further once resting pressures reach the hypertensive range, suggesting persistent maximal demands on these antinociceptive systems among hypertensive individuals. (C) 2013 by the American Pain Society