Objectives: To determine the effect of duloxetine treatment on cognition in patients with fibromyalgia.
Methods: Cognitive testing was conducted in a subset of adult patients in a randomized, double-blind, placebo-controlled trial of duloxetine. Patients met the American College of Rheumatology criteria for fibromyalgia and had a score of 4 or higher on the Brief Pain Inventory 24-hour average pain severity item. Patients who consented to cognitive testing were randomized to duloxetine (n = 80) or placebo (n = 76). The primary end point was at Week 12. Speed of processing on tasks requiring visual attention, working memory, and executive function was assessed with a Symbol Digit Substitution Test and Trail-Making Test A and B. Episodic memory was tested using the Verbal Learning and Recall Test. The change from baseline to end point (last-observation-carried-forward analysis) was analyzed by an analysis of covariance model, which included baseline, treatment, investigator, and treatment-by-investigator interaction.
Results: Most of the patients were white (89%) women (92%), ranging in age from 21 to 88 years. Mean scores on the cognitive tests were within 2 SD of published scores for similar-aged participants in the general population, indicating no substantial impairment. Baseline-to-end point changes in cognitive scores did not differ significantly between duloxetine and placebo treatment groups.
Conclusions: Although scores differed somewhat from norms for age, substantial cognitive impairment was not evident in patients with fibromyalgia as assessed by the Symbol Digit Substitution Test, Trail-Making Test, and Verbal Learning and Recall Test. Overall, duloxetine treatment had neither positive nor negative effects on cognition.
Trial registration: Clintrials.gov NCT00673452.