Non-steroidal anti-inflammatory drug use and risk of venous thromboembolism

Background: The association between the use of non-selective non-steroidal anti-inflammatory drugs (NSAIDs) or cyclooxygenase-2-selective inhibitors (COX2Is) and the risk of venous thromboembolism (VTE) remains unclear. Objectives: To examine this association. Patients/Methods: We conducted a population-based case-control study in northern Denmark (population of 1.7 million). Using the National Patient Registry, we identified patients with a first hospital VTE diagnosis during 1999-2006 (n = 8368) and their comorbidities. For each case, we selected 10 controls (n = 82 218) matched by age and sex. From the prescription database, we ascertained the use of NSAIDs at the time of diagnosis (current use) or before (recent use), and comedications. Current use was further classified as new use (first-ever prescription redemption within 60 days before diagnosis date) or long-term use. We used odds ratios from a logistic regression model to estimate incidence rate ratios (IRRs) with 95% confidence intervals (CIs). Results: As compared with no use, the adjusted IRR associating current non-selective NSAID use with VTE was 2.51 (95% CI 2.29-2.76), and that for current COX2I use was 2.19 (95% CI 1.99-2.41). Recent users had substantially smaller increases than current users. The adjusted IRRs among long-term users were 2.06 for non-selective NSAIDs (95% CI 1.85-2.29) and 1.92 for COX2Is (95% CI 1.72-2.15). Similarly increased risks were found for unprovoked VTE (occurrence in the absence of pregnancy, cancer, major trauma, fracture or surgery within 3 months preceding the VTE), deep vein thrombosis, pulmonary embolism, and individual NSAIDs. Conclusions: The use of non-selective NSAIDs or COX2Is was associated with a two-fold or more increased risk of VTE.