Eszopiclone treatment for insomnia: effect size comparisons in patients with primary insomnia and insomnia with medical and psychiatric comorbidity.
OBJECTIVE: The purpose of this post hoc analysis was to compare the treatment effect size of eszopiclone 3 mg for insomnia in patients with a diagnosis of primary insomnia and in several of the psychiatric and medical conditions that are most commonly comorbid with insomnia. METHOD: Data were analyzed from 5 large, multicenter, randomized, double-blind, placebo-controlled studies of adult outpatients of at least 1 month duration published between 2006 and 2009. Diary-derived indices of sleep and daytime functioning and the Insomnia Severity Index were compared for patients with primary insomnia (DSM-IV-TR criteria, n = 828) and for those with insomnia comorbid with major depressive disorder (MDD, DSM-IV-TR criteria, n = 545), generalized anxiety disorder (GAD, DSM-IV-TR criteria, n = 595), perimenopause/postmenopause (Stages of Reproductive Aging Workshop criteria, n = 410), and rheumatoid arthritis (American College of Rheumatology criteria, n = 153). Cohen d effect sizes were calculated for each individual study as the between-treatment difference score divided by the pooled standard deviation. RESULTS: Effect sizes ranged from 0.40 to 0.69 (small-medium) as early as week 1 and were maintained at 0.26-0.63 at week 4 for sleep latency, wake time after sleep onset, and total sleep time. Sleep latency and total sleep time effect sizes increased from week 1 to week 4 in the primary insomnia group. At week 4, effect sizes on all 3 parameters and the Insomnia Severity Index tended to be highest for the primary insomnia patients and tended to be lowest for patients with comorbid GAD and MDD. The effect sizes for daytime functioning were small for all insomnia patient groups. CONCLUSIONS: Eszopiclone 3 mg is an effective treatment for insomnia across 5 clinically diverse patient populations; however, magnitude of effect is mediated by underlying comorbidity and their treatments, with largest measures of effect seen in primary insomnia and lowest in MDD and GAD. These consistent results, and the fact that clinical trials were conducted in patients being treated as appropriate for their comorbid clinical conditions, support the results' real-world generalizability and utility to clinical practice.
