Age-associated differences in responses to noxious stimuli

Background. Although population-based studies typically report age-associat ed increases in clinical pain, laboratory-based pain assessment procedures generally indicate diminished pain sensitivity with age. The majority of th ese studies have utilized noxious thermal stimuli as the method of pain ind uction. However, other pain assessment methodologies, including ischemic pa in induction, may have a more meaningful relationship to clinical pain. The present study examined the effects of age on responses to a variety of exp erimental noxious stimuli. In addition, relationships between cardiovascula r measures and pain responses were investigated in both older and younger s ubjects. Methods. Responses to thermal. mechanical, and ischemic pain were assessed in 34 younger (mean age, 22.4 years) and 34 older adults (mean age, 62.2 ye ars). In addition, relationships between resting blood pressure and pain re sponses were assessed separately for older and younger participants. Results. Although group differences in thermal and mechanical pain response s did not achieve statistical significance, older individuals demonstrated substantially lower ischemic pain thresholds and tolerances assessed via th e modified submaximal effort tourniquet procedure (ps < .01). Overall. high er resting arterial blood pressures were associated with increased pain thr esholds and tolerances, although relationships between blood pressure and i schemic pain variables were evident only for the younger group. Conclusions. These findings indicate that age-related differences in respon ses to experimental noxious stimuli vary as a function of the pain inductio n task, with older individuals showing greater sensitivity to clinically re levant stimuli. In addition, the absence of a relationship between blood pr essure and ischemic pain responses in older adults may suggest potential fu nctional decrements in at least one endogenous pain-modulatory system.