Use of statins and the subsequent development of deep vein thrombosis

Background: Some of the benefit of statins for the prevention of cardiovasc ular 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 databa ses covering more than 1.4 million Ontario residents aged 65 years or older . We excluded those with a documented history of atherosclerosis, venous th romboembolism, or cancer within 36 months prior to study enrollment, as wel l as these prescribed warfarin sodium within 12 months before enrollment. I n the primary cohort, we evaluated the subsequent risk of deep vein thrombo sis (DVT) among men and women prescribed thyroid replacement therapy, nonst atin lipid-lowering agents, or statins. A second cohort of women only was e valuated in a similar fashion, but estrogen use was added as a third compar ison drug group. Results: There were 12 5862 men and women in the primary cohort. After adju sting for age; sex; prior hospitalization; newly diagnosed cancer; or presc ribed aspirin, warfarin, or estrogen, statin users (n = 77 993) had an asso ciated decreased risk of DVT relative to those prescribed thyroid replaceme nt therapy (n = 35978) (adjusted hazard ratio [HR], 0.78; 95% confidence in terval [CI], 0.69-0.87). Compared with thyroid replacement therapy, users o f nonstatin lipid-lowering agents (n = 11891) did not seem to be at lower r isk for deep vein thrombosis (HR, 0.97; 95% CI, 0.79-1.18). In the secondar y cohort of 89 508 women, after adjusting for age, prior hospitalization, n ewly diagnosed cancer, or prescribed aspirin or warfarin, estrogen users (n = 29165) had an associated increased risk for DVT compared with those rece iving thyroid replacement therapy (n = 22118) (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 wi th a reduced risk of DVT compared with thyroid replacement therapy (HR, 0.8 4; 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 random ized clinical trial is needed to evaluate the efficacy of statins for the p rimary and secondary prevention of DVT.