(325) Does Time Variation between Study Visits Relate to Differences in Pain Ratings

Abstract

Experimental pain research often requires research participants to complete multiple study visits. Variability in the time difference between study visits may be a factor that should be controlled for in pain research. We aim to investigate the question of how variation in the time interval between two study visits affects pain ratings and whether anxiety or pain catastrophizing moderate this effect. During the first visit (V1), participants rated pain intensity (visual analog scale) after each noxious heat stimulus in a series (7 stimuli of 48°C, 10 seconds each). In addition, subjects completed self-reported measures for anxiety (PROMIS® Anxiety) and pain catastrophizing (Pain Catastrophizing Scale). The second visit (V2) included a repeat of the self-report measures and the same noxious heat stimuli during an MRI scan. Pain intensity ratings of the 48°C stimuli were averaged for each visit, and difference scores (V2 minus V1), as well as the percent change [(average intensity V2 minus average intensity V1)/average intensity V1], were calculated for each participant. This is a secondary analysis of 100 healthy adults (31 males, 69 females, age 28.8±6.8) from the parent study. The average difference between study visits was 20.1±20.5 days (range: 1 to 83 days). No significant correlations were identified for the time difference between study visits and pain intensity rating difference (p=0.166), and including anxiety and pain catastrophizing into the analysis did not affect the relationships (p=0.715 and p=0.262 respectively). Similar results were found using percent reduction in pain ratings. Sex and age were included in the models and did not have a significant effect on the relationships. The realities of human research make it difficult to schedule multiple study visits at exact time intervals. Despite variable time between study visits, time difference does not appear to have a significant effect on pain ratings in healthy adults.