Use of Statins and the Subsequent Development of Deep Vein Thrombosis

BACKGROUND: Some of the benefit of statins for the prevention of cardiovascular disease may be due to their antithrombotic properties. Little is known about the effect of these drugs on the development of deep vein thrombosis. MATERIALS AND METHODS: We conducted a retrospective cohort study over an 8-year period by linking Ontario provincial health care administrative databases covering more than 1.4 million Ontario residents aged 65 years or older. We excluded those with a documented history of atherosclerosis, venous thromboembolism, or cancer within 36 months prior to study enrollment, as well as those prescribed warfarin sodium within 12 months before enrollment. In the primary cohort, we evaluated the subsequent risk of deep vein thrombosis (DVT) among men and women prescribed thyroid replacement therapy, nonstatin lipid-lowering agents, or statins. A second cohort of women only was evaluated in a similar fashion, but estrogen use was added as a third comparison drug group. RESULTS: There were 125 862 men and women in the primary cohort. After adjusting for age; sex; prior hospitalization; newly diagnosed cancer; or prescribed aspirin, warfarin, or estrogen, statin users (n = 77 993) had an associated decreased risk of DVT relative to those prescribed thyroid replacement therapy (n = 35 978) (adjusted hazard ratio HR, 0.78; 95% confidence interval CI, 0.69-0.87). Compared with thyroid replacement therapy, users of nonstatin lipid-lowering agents (n = 11 891) did not seem to be at lower risk for deep vein thrombosis (HR, 0.97; 95% CI, 0.79-1.18). In the secondary cohort of 89 508 women, after adjusting for age, prior hospitalization, newly diagnosed cancer, or prescribed aspirin or warfarin, estrogen users (n = 29 165) had an associated increased risk for DVT compared with those receiving thyroid replacement therapy (n = 22 118) (HR, 1.16; 95% CI, 1.01-1.33), while statin users had an associated decreased risk (HR, 0.68; 95% CI, 0.59-0.79). Nonstatin lipid-lowering agents (n = 5155) were not associated with a reduced risk of DVT compared with thyroid replacement therapy (HR, 0.84; 95% CI, 0.63-1.12). CONCLUSION: Among selected individuals aged 65 years or older, statins were associated with a 22% relative risk reduction in the risk of DVT. A randomized clinical trial is needed to evaluate the efficacy of statins for the primary and secondary prevention of DVT.