Research Description

Differences in Pain Modulation Across the Lifespan

Previous studies have shown that older adults experience a more significant amount of clinical pain believed to be related to less effective pain modulation, which explains a higher incidence of chronic pain. Diffuse noxious inhibitory control (DNIC) is a pain modulating system characterized by pain inhibiting pain. DNIC in believed to inhibit pain at the level of the spinal column. DNIC studies on aging in the past have looked at tolerance and threshold measures but never the effect with prolonged thermal stimulation.

The purpose of this study is to look at the effect of aging on DNIC efficacy. We have hypothesized that older individuals will experience a less robust pain inhibition than younger individuals due to a less effective pain modulating system associated with DNIC.

We plan on comparing 8 – 12 older adults with 8 – 12 younger controls. We have designed several protocols (control and DNIC) using a thermode applied to the left palm (experimental stimulus) in combination with a cold water bath applied to the right foot (conditioning stimulus). Each participant will undergo a training session that will acclimate them to rating heat and cold pain using an electronic visual analog scale (eVAS). The eVAS is defined form 0 (no pain) to 100 (intolerable pain). Each session will consist of 5 60-second trials applying the experimental stimulus and conditioning stimulus concurrently. One session will be performed using a non-painful water bath temperature, while one will be performed using the painful water bath temperature determined from the training session. The difference in the pain ratings for these two trials related to the heat pain will be the DNIC effect.

Previous studies have shown DNIC efficacy to be a valid predictor of post-operative pain.