(250) The Relationship between Beta-Endorphin and Experimental Pain Sensitivity in Older Adults with Knee Osteoarthritis Pain

Abstract

Osteoarthritis (OA) is the most common arthritic condition and a leading cause of pain and disability in people 45 years and older. As the biopsychosocial model of pain hypothesizes that pain is dynamically affected by multidimensional factors, there is a growing interest to understand the biological factors that influence pain among older adults. Beta-endorphin is suggested to be involved in pain sensitivity, but few studies have examined the relationship between beta-endorphin and experimental pain sensitivity in older adults. Thus, we sought to investigate the relationship between beta-endorphin and experimental pain sensitivity in 40 adults with knee OA pain. Pressure pain thresholds were measured by a handheld Medoc digital pressure algometer. Also, a calibrated nylon monofilament delivering a target force of 300 grams was applied and verbal ratings of the pain intensity on a scale of 0 to 100 following 10 contacts were obtained to assess their sensitivity to punctate mechanical stimuli. The mean age was 59 years (SD = 9 years), and 53% were female. Results showed that beta-endorphin is negatively related to pressure pain threshold (beta = -0.35, t = -2.40, p = 0.02) and positively related to punctate mechanical pain (beta = 0.34, t = 2.14, p = 0.04), after controlling for age, gender, and OA severity. These results suggest that higher circulating beta-endorphin at rest is associated with increased sensitivity to mechanical pain in older adults with knee OA. Further studies are needed to explore these paradoxical associations and to identify variables mediating the relationship between endorphin and pain sensitivity.