Presentation: Catastrophizing and Fatigue are Associated with Poorer Perceived Physical Function Relative to Objective Activity Measures in Fibromyalgia (2007)

1527 Catastrophizing and Fatigue are Associated with Poorer Perceived Physical Function Relative to Objective Activity Measures in Fibromyalgia

Purpose: Patients with fibromyalgia (FM) have low levels of self-reported physical function, compared to either controls or other chronic illnesses. We have previously shown that in both FM patients and controls, there are poor relationships between self-reported function, and objective activity levels as measured by actigraphy. This study examined the potential reasons for the differences between self-reported function and activity levels in FM by examining the symptoms and psychological factors most strongly associated with these discrepanices.
Methods: 31 patients with FM (43.1 ± 8.2 years, 71% women) completed 5 days of ambulatory monitoring of physical activity, using a wristwatch-sized omni-directional accelerometer (Actiwatch-Score). Activity counts were recorded continuously and summed over 5-min epochs. Peak and average activity were defined as the peak and average activity count over all epochs, respectively. Self-reported physical function was measured using the SF36 physical functioning subscale (PF) after completion of the 5-day period. Measures of fatigue (Multidimensional Fatigue Inventory), catastrophizing (Coping Strategies Questionnaire, Catastrophizing subscale), depression (CES-D), anxiety (State-Trait Personality Inventory, Trait Anxiety subscale) and pain (McGill Pain Questionnaire) were also assessed. Data were analyzed using SPSS v.14. Discrepancies between activity (peak and average) and PF scores were calculated as the difference between normalized values, and Pearson’s correlation coefficients were obtained among all variables. Simultaneous linear regression models were created to predict peak activity, average activity, and discrepancies between these measures and PF scores; all other variables with significance of correlation < .50 were used as independent variables. Hierarchical regression models were created to check for co-linearity.
Results: SF36 PF scores did not correlate with either peak or average activity (p = .48 and .15, respectively). Catastrophizing (r = .529, p < .01) and fatigue (r = .521, p < .01) significantly correlated with the degree to which average activity exceeded PF score. Catastrophizing (r = .404, p < .05) and fatigue (r = .423, p < .05 ) also correlated with the degree to which peak activity exceeded PF score. The linear regression model for predicting discrepancy between average activity and PF score was significant (R2 = .632, p = .002), and co-linearity was not observed between fatigue and catastrophizing. These discrepancies did not correlate with levels of pain, depression, and anxiety.
Conclusion: Measures of self-reported physical function using the SF36 PF do not correlate with objective measures of activity in FM patients. Higher levels of fatigue and catastrophizing are independently associated with poorer perceived function compared to actigraphy.

 M.C. Hsu, None; M.E. Geisser, None; A.K. Lyden, None; D.A. Williams, NIH, 2; Cypress BioScience, 5; D.J. Clauw, Department of Defense, Cooperative Agreement, 2; Cypress BioScience, 5; Lilly, 5; Forest, 5; Pfizer, 5; Wyeth, 5.