1247: Relation of Measures of Pain Sensitization to Widespread Pain

Background/Purpose: Widespread pain (WSP) is thought to be related to alterations in nociceptive signaling such as pain sensitization. Whether pain sensitization predisposes to an increase in number of pain sites, including the development of WSP, is not known.

Methods: We included participants from the Multicenter Osteoarthritis Study (MOST), a NIH-funded longitudinal cohort, who reported pain sites on a homunculus at baseline and two years later to determine WSP status (defined as pain above and below the waist, on the right and left sides of the body, and axially), and underwent quantitative sensory testing (QST). We assessed baseline pain sensitization (i.e., alterations in ascending nociceptive signaling) using three QST measures: temporal summation (TS) at the wrist, and pressure pain threshold (PPT) at the patella (average of both knees), and PPT at the wrist. Higher TS indicates more pain sensitization, while higher PPT indicates less pain sensitization.

We analyzed the relations of QST to: 1) the presence of WSP at baseline; 2) an increase of at least two painful sites after two years of follow-up; and 3) incident WSP after two years among those who were free of WSP at baseline. We used logistic regression to estimate presence of WSP at baseline, and modified Poisson regression for the longitudinal analyses. We secondarily performed sex-stratified analyses given known sex differences in QST. All analyses were adjusted for potential confounders, including age, sex (for analyses of the whole sample), BMI, race, site, presence of symptomatic knee osteoarthritis in at least one knee, depressive symptoms, NSAID use, Opioid use, and Charlson comorbidity index.

Results: We included 3078 participants (mean age 62.7, 57.7% female), of whom 32.2% had WSP at baseline (67.8% female), and 23.5% had an increase in two or more painful sites (59.8% female) at two years of follow-up. Among the 2088 participants free of WSP at baseline (mean age 62.1, 52.9% female), 14.9% had incident WSP (55.9% female) over two years. Cross-sectionally, TS was significantly associated with baseline WSP in the whole sample and in females but not in males (Table). PPT at the wrist was inversely associated with baseline WSP in the whole sample and in both sexes, while PPT at the patella was inversely associated in the whole sample and female participants, but not in males (Table). There were no significant associations between QST measures and either an increase in at least two painful sites or incidence of WSP after two years of follow-up (Table).

Conclusion: Although QST measures were associated with WSP cross-sectionally, they were not associated with incident WSP or increase in number of pain sites over two years. However, the null longitudinal findings may have been limited by the phenomenon of depletion of susceptibles (i.e., those most susceptible had already developed WSP in relation to pain sensitization at an earlier age).