Placebo analgesia refers to a perceived reduction in pain following the administration of a simulated or otherwise medically ineffective treatment. Previous studies have shown that many factors can influence placebo analgesia. However, few investigations have examined the effect of age on placebo analgesia, and none have done it in the context of rehabilitation interventions. The objective of this study was to compare the placebo response induced by sham transcutaneous electrical nerve stimulation (TENS) between young and older individuals, using an experimental heat-pain paradigm.

Twenty-two young (21–39 years) and 22 older (58–76 years) healthy adults participated in this comparative study. Experimental heat-pain was evoked with a thermode (2-min stimulation at a constant, individually adjusted temperature) applied on the lumbar region. Participants were asked to evaluate the intensity of their pain using a computerized visual analog scale. Experimental pain was induced before and after an unconditioned placebo intervention (sham TENS).

In young individuals, no significant pain reductions were noted, whereas in older individuals, a statistically significant pain reduction was observed after the placebo stimulation (P<0.01). Between-group analysis revealed that placebo analgesia was greater in older individuals (40% pain reduction) compared to young individuals (15% reduction; P<0.05).

Our results indicate that placebo analgesia is influenced by age, with older individuals showing higher placebo analgesia than young adults. Although these results should be confirmed in clinical pain populations, the current observations bear important consequences for the design of future placebo-controlled trials in rehabilitation and for healthcare professionals.