AN EXAMINATION OF DAY-TO-DAY AND INTRAINDIVIDUAL PAIN VARIABILITY IN LOW BACK PAIN.

OBJECTIVE This study aimed to capture day-to-day changes in pain intensity in individuals with low back pain (LBP), which may be indicative of patients' ability to modulate their pain levels. A secondary aim was to explore the presence of latent subgroups characterized by pain level, intraindividual pain variability, and change in pain over a 14-day period. SUBJECTS Participants were 54 adults with self-reported low back pain recruited from outpatient Physical Therapy clinics and the community. METHODS Over the course of 14 days, participants completed daily measures of pain intensity, catastrophizing, pain self-efficacy, and negative affect. Change in pain intensity as well as total amount of intraindividual pain variability were also calculated. RESULTS Daily increases in maladaptive coping and affective responses (i.e., higher catastrophizing, higher negative affect, lower pain self-efficacy) were associated with increases in pain intensity. A hierarchical cluster analysis revealed three subgroups: (1) moderate pain intensity, moderate pain variability, increase in pain over time; (2) low pain intensity, low pain variability, no change in pain over time; and (3) moderate pain intensity, high pain variability, decrease in pain over time. Cluster 2 demonstrated more adaptive coping and affective responses at baseline and during the 14-day period, and Cluster 1 and 3 did not differ in their coping nor affective responses. CONCLUSIONS These findings provide support that day-to-day changes in pain, coping and affective responses are meaningful and provide additional evidence of pain variability as a potential phenotypic characteristic.