Abstract
BACKGROUND: Anxiety disorders are among the most common psychiatric illnesses, with generalized anxiety disorder (GAD) being one of the most common. Sleep disturbances are highly prevalent in GAD patients. While treatment with pregabalin has been found to be associated with significant improvement in GAD-related sleep disturbance across many controlled clinical trials, mediational analysis has suggested that a substantial portion of this effect could be the result of a direct effect of pregabalin. Thus, the objective of this study was to model the longitudinal latent effect of pregabalin or usual care (UC) therapies on changes in sleep in outpatients with GAD under routine clinical practice. METHODS: Male and female GAD outpatients, aged 18 years or above, from a 6-month prospective noninterventional trial were analyzed. Direct and indirect effects of either pregabalin or UC changes in anxiety symptoms (assessed with Hamilton Anxiety Scale) and sleep disturbances (assessed with Medical Outcomes Study-Sleep Scale [MOS-S]) were estimated by a conditional latent curve model applying structural equation modeling. RESULTS: A total of 1,546 pregabalin-naïve patients were analyzed, 984 receiving pregabalin and 562 UC. Both symptoms of anxiety and sleep disturbances were significantly improved in both groups, with higher mean (95% confidence interval) score reductions in subjects receiving pregabalin: -15.9 (-15.2; -16.6) vs -14.5 (-13.5; -15.5), P=0.027, in Hamilton Anxiety Scale; and -29.7 (-28.1; -31.3) vs -24.0 (-21.6; -26.4), P<0.001, in MOS-S. The conditional latent curve model showed that the pregabalin effect on sleep disturbances was significant (γ =-3.99, P<0.001), after discounting the effect on reduction in anxiety symptoms. A mediation model showed that 70% of the direct effect of pregabalin on sleep remained after discounting the mediated effect of anxiety improvement. CONCLUSION: A substantial proportion of the incremental improvements in anxiety-related sleep disturbances with pregabalin vs UC were explained by its direct effect, not mediated by improvements in anxiety symptoms.