Objective evidence of decreased pain perception in normotensives at risk for hypertension

Results from laboratory and naturalistic studies have demonstrated decreased subjective pain ratings in hypertensives and individuals at risk for hypertension. Based on previous evidence that the nociceptive withdrawal reflex may provide an objective index of pain threshold in humans, the present study examined the intensity of sural nerve stimulation required to elicit nociceptive withdrawal in offspring of hypertensives and normotensives. Participants included 60 men and 56 women who were normotensive, 18-23 years of age, and predominately Caucasian. To assess the nociceptive withdrawal reflex, ascending and descending intensities of electrical stimulation were applied over the sural nerve while electromyographic activity was recorded from the ipsilateral biceps femoris muscle. Analyses of the intensity of electrical stimulation required to reach the thresholds for nociceptive withdrawal and subjective pain revealed a pattern of hypoalgesia in individuals at risk for hypertension. First, significantly higher intensities were required to elicit nociceptive withdrawal in offspring of hypertensives versus normotensives. Second, offspring of hypertensives endured significantly more intense stimulation before reporting pain. Third, both parental history of hypertension and resting systolic blood pressure were significant independent predictors of stimulation intensity at nociceptive withdrawal reflex and subjective pain thresholds. These results confirm and extend previous observations of an association between risk for hypertension and hypoalgesia, and suggest that hypoalgesia should be examined as a potential predictor of progressive blood pressure increases in individuals at risk for hypertension.