The Magnitude of Offset Analgesia as a Measure of Endogenous Pain Modulation in Healthy Participants and Patients With Chronic Pain

Abstract

Objective: Offset analgesia (OA) is a test paradigm increasingly used to estimate endogenous pain modulation characterized by a disproportionally profound analgesia after a small decrease of a heat stimulus. This systematic review and meta-analysis examined the magnitude and difference of OA in healthy participants and chronic pain patients. Materials and Methods: Controlled trials, case-control studies, cross-sectional studies, case-series or other observational studies evaluating the effect of a ±1°C offset trial in healthy controls and patients with chronic pain were searched in PubMed, Web of Science, CINAHL, PEDro, PsycINFO, and Cochrane CENTRAL. An additional hand search was conducted. Studies fulfilling the eligibility criteria were independently assessed for methodological quality with the Downs and Black scale by 2 reviewers. Results: Twenty-six studies (healthy participants n=758; chronic pain patients n=134) were included in the qualitative synthesis and 12 in meta-analyses (healthy participants n=366; chronic pain patients n=73). A significant difference between offset and constant temperature trials was found for continuous pain intensity rating immediately after a 1°C decrease in temperature (−0.46 [visual analogue scale, 0 to 10]; 95% confidence interval, −0.75 to −0.17; P=0.002), but not after a fixed time period of 5 seconds. Furthermore, a significant difference of the magnitude of OA between chronic pain patients and healthy controls was calculated (−29.9%; 95% confidence interval, −40.3 to −19.5; P<0.00001). Discussion: Results indicate that pain-free participants show a larger OA response when rating pain continuously compared with individuals with chronic pain.

Endogenous pain modulation assessed with offset analgesia is not impaired in chronic temporomandibular disorder pain patients

“…This is distinct from the presentation of chronic TMD pain patients, in whom clinical pain affects mostly the jaw and face — even though comorbid pain conditions are relatively common in this population . Clinical and psychosocial characteristics of the chronic TMD cases included in the present study were similar to those reported by the OPPERA case‐control study and to previous studies comparing OA responses in pain patients relative to controls . This similarity reduces the likelihood that clinical and psychosocial characteristics of our sample would suffice to explain the lack of OA response differences between chronic TMD cases and controls.…”

“…Delta COVAS for TMD cases (mean ± SD: 53.5 ± 22) and controls (51.6 ± 22.9) were relatively similar to the reported mean for healthy controls of similar age range described by Niesters et al: age 20‐39 years (n = 14): 45.3 ± 7.1; 40‐59 years (n = 23): 51.8 ± 4.5. This further supports that TMD participants present with similar OA response as pain‐free controls when tested over the forearm, the body test site most commonly used to assess OA responses . One study tested OA responses not only over the forearm but also over the thenar eminence of healthy, pain‐free participants and found no significant OA response in the latter, suggesting that OA may be site‐specific.…”

“…Previous studies assessing OA response in clinical pain populations reported it as impaired relative to controls . The first study to test OA in pain patients compared 10 neuropathic pain patients with symptoms affecting the arms and/or legs to matched controls and found that patients presented substantially reduced OA .…”

“…Based on findings from our pilot study, we used individual TT (pain‐30) that evoked a statistically significant OA response in both groups. Previous studies have used either fixed temperatures, for example, 48‐49‐48ºC, or individual TT evoking higher pain ratings, for example, pain‐50. It is possible that use of higher individual TT during OA testing could reveal differences in OA responses between chronic TMD pain cases and controls.…”

“…Several studies have found that OA is significantly reduced in chronic pain patients when compared to pain‐free controls . These studies included patients diagnosed with neuropathic pain, fibromyalgia or a mix of chronic pain conditions .…”