Age does not affect sex effect of conditioned pain modulation of pressure and thermal pain across 2 conditioning stimuli.

Conditioned pain modulation (CPM) is a laboratory test resulting in pain inhibition through activation of descending inhibitory mechanisms. Older adults consistently demonstrate reduced CPM compared with younger samples; however, studies of sex differences in younger cohorts have shown mixed results. This study tested for sex differences in CPM within samples of younger and older adults. Participants were 67 younger adults (mean age = 25.4 years) and 50 older adults (66.4 years). Study conditioning paradigms were the cold-pressor test and contact heat pain administered in separate sessions. Pressure pain threshold and ramping suprathreshold heat were the test stimuli across three time points after presentation of the conditioning stimuli (CS). Significant inhibition was observed during both testing sessions. The hypothesis for sex differences across both age cohorts was supported only for ∆PPTh. However, sex differences did not reach significance for either paradigm using ascending suprathreshold heat as the test stimuli. The overall trend was that younger males experienced the strongest CPM and older females the weakest. From a methodological perspective, duration differences were seen in CPM, with inhibition decaying more quickly for PPTh than for suprathreshold heat pain. Furthermore, there were no differences in inhibition induced by cold-pressor test and contact heat pain as CS. Sex differences were similar across both age cohorts with males experiencing greater inhibition than females. Cross-sectional associations were also demonstrated between CPM inhibition and measures of recent pain, further supporting CPM as an experimental model with clinical utility.

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Copyright © 2019 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The International Association for the Study of Pain.

Déclaration de conflit d'intérêts

R.B. Fillingim has received consulting fees, speaking fees, and/or honoraria from WebMD and Algynomics (less than $10,000 each) and owns stock or stock options in Algynomics. The remaining authors have no conflicts of interest to declare. This research was supported by NIH-NIA Grant R01AG039659.Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.