IMI PROTECT(WP2): Antidepressants & Fractures

The studies described in this protocol are all performed within the framework of PROTECT (Pharmacoepidemiological Research on Outcomes of Therapeutics by a European ConsorTium) Workpackage 2 and Workgroup 1. Primary aim of these studies is to develop, test and disseminate methodological standards for the design, conduct and analysis of Pharmacoepidemiological (PE) studies applicable to different safety issues and using different data sources. To achieve this, results from PE studies on five key adverse events (AEs) performed in different databases will be evaluated. Therefore, emphasis will be on the methodological aspects of the studies in this protocol and not on the clinical consequences of the association under investigation. Fracture of the proximal end of the femur or hip is associated with considerable morbidity and mortality. Hip/femur fractures impair quality of life and impose a considerable economic burden, and occur with 20% mortality rate within the first year. Antidepressants (AD), mainly tricyclic AD (TCAs) and selective serotonin re-uptake inhibitors (SSRIs) have been associated with fractures in several studies. A review of 13 observational studies showed risk ratios ranging from 1.2 to 3.7 for current TCA users and a wide range of 1.5 to 8.6 for SSRI users. The majority of the studies in the aforementioned review reported increased risks of fractures in general with SSRIs use and more mixed risk outcomes for TCA use. Several mechanisms underlying this adverse effect have been postulated in the literature: e.g. through decrease in bone mineral density (BMD) or through blocking the serotonin transporter activity (5-hydroxytryptamine re-uptake) and hence affecting bone metabolism and structure or simply by falling or through co-morbidities such as depression itself. Previous observational studies differ in design, conduct and analysis of the considered association with varying degree of accounting for confounders. Confounding factors such as depressi