OBJECTIVE EVIDENCE OF DECREASED PAIN PERCEPTION IN NORMOTENSIVES AT RISK FOR HYPERTENSION

Results from laboratory and naturalistic studies have demonstrated dec reased subjective pain ratings in hypertensives and individuals at ris k for hypertension. Based on previous evidence that the nociceptive wi thdrawal reflex map provide an objective index of pain threshold in hu mans, the present study examined the intensity of sural nerve stimulat ion required to elicit nociceptive withdrawal in offspring of hyperten sives and normotensives. Participants included 60 men and 56 women who were normotensive, 18-23 years of age, and predominately Caucasian. T o assess the nociceptive withdrawal reflex, ascending and descending i ntensities of electrical stimulation were applied over the sural nerve while electromyographic activity was recorded from the ipsilateral bi ceps femoris muscle. Analyses of the intensity of electrical stimulati on required to reach the thresholds for nociceptive withdrawal and sub jective pain revealed a pattern of hypoalgesia in individuals at risk for hypertension. First, significantly higher intensities were require d to elicit nociceptive withdrawal in offspring of hypertensives versu s normotensives. Second, offspring of hypertensives endured significan tly more intense stimulation before reporting pain. Third, both parent al history of hypertension and resting systolic blood pressure were si gnificant independent predictors of stimulation intensity at nocicepti ve withdrawal reflex and subjective pain thresholds. These results con firm and extend previous observations of an association between risk f or hypertension and hypoalgesia, and suggest that hypoalgesia should b e examined as a potential predictor of progressive blood pressure incr eases in individuals at risk for hypertension. (C) 1997 International Association for the Study of Pain. Published by Elsevier Science B.V.