 Effect of Statins on Venous Thromboembolic Events: A Meta-analysis of Published and Unpublished Evidence from Randomised Controlled TrialsKazem Rahimi, Neeraj Bhala, Pieter Kamphuisen, Jonathan Emberson, Sara Biere-Rafi, Vera Krane, Michele Robertson, John Wikstrand and John McMurray PLOS Medicine, 2012, vol. 9, issue 9, 1-13 Abstract: A systematic review and meta-analysis conducted by Kazem Rahimi and colleagues re-evaluates the hypothesis, generated in previous studies, that statins may reduce the risk of venous thromboembolic events. Their meta-analysis does not support the previous findings. Background: It has been suggested that statins substantially reduce the risk of venous thromboembolic events. We sought to test this hypothesis by performing a meta-analysis of both published and unpublished results from randomised trials of statins. Methods and Findings: We searched MEDLINE, EMBASE, and Cochrane CENTRAL up to March 2012 for randomised controlled trials comparing statin with no statin, or comparing high dose versus standard dose statin, with 100 or more randomised participants and at least 6 months' follow-up. Investigators were contacted for unpublished information about venous thromboembolic events during follow-up. Twenty-two trials of statin versus control (105,759 participants) and seven trials of an intensive versus a standard dose statin regimen (40,594 participants) were included. In trials of statin versus control, allocation to statin therapy did not significantly reduce the risk of venous thromboembolic events (465 [0.9%] statin versus 521 [1.0%] control, odds ratio [OR] = 0.89, 95% CI 0.78–1.01, p = 0.08) with no evidence of heterogeneity between effects on deep vein thrombosis (266 versus 311, OR 0.85, 95% CI 0.72–1.01) and effects on pulmonary embolism (205 versus 222, OR 0.92, 95% CI 0.76–1.12). Exclusion of the trial result that provided the motivation for our meta-analysis (JUPITER) had little impact on the findings for venous thromboembolic events (431 [0.9%] versus 461 [1.0%], OR = 0.93 [95% CI 0.82–1.07], p = 0.32 among the other 21 trials). There was no evidence that higher dose statin therapy reduced the risk of venous thromboembolic events compared with standard dose statin therapy (198 [1.0%] versus 202 [1.0%], OR = 0.98, 95% CI 0.80–1.20, p = 0.87). Risk of bias overall was small but a certain degree of effect underestimation due to random error cannot be ruled out. Conclusions: The findings from this meta-analysis do not support the previous suggestion of a large protective effect of statins (or higher dose statins) on venous thromboembolic events. However, a more moderate reduction in risk up to about one-fifth cannot be ruled out. Background: Blood normally flows smoothly throughout the human body, supplying its organs and tissues with oxygen and nutrients. But, when an injury occurs, proteins called clotting factors make the blood gel (coagulate) at the injury site. The resultant blood clot (thrombus) plugs the wound and prevents blood loss. Occasionally, however, a thrombus forms inside an uninjured blood vessel and partly or completely blocks the blood flow. A clot inside one of the veins (vessels that take blood towards the heart) deep within the body is called a deep vein thrombosis (DVT). Symptoms of DVT (which usually occurs in the leg) include pain, swelling, and redness in the affected limb. DVT is treated with heparin and warfarin, two anticoagulant drugs that stop the blood clot growing. If left untreated, part of the clot (an embolus) can break off and travel to the lungs, where it can cause a pulmonary embolism (PE), a life-threatening condition characterized by chest pain, breathlessness, coughing, and dizziness. Little is known about how to prevent DVTs and PEs but risk factors for these venous thromboembolic events include having an inherited blood clotting disorder, oral contraceptive use, having surgery, and prolonged inactivity (on long-haul plane flights, for example). Why Was This Study Done?: In 2009, a secondary (add-on) analysis of data from a randomized controlled trial (RCT, a study that randomly assigns individuals to receive different treatments and compares the outcomes associated with each treatment) called the JUPITER trial reported that rosuvastatin—a cholesterol-lowering drug (statin)—halved the risk of venous thromboembolic events among apparently healthy adults. The JUPITER trial was initiated to test whether statins reduce the risk of strokes, heart attacks, and other cardiovascular diseases (conditions that involve the heart and the blood vessels) among adults with raised levels of a predictor for these diseases called C-reactive protein; statins reduce the levels of this protein as well as those of cholesterol. Because fewer than 100 of the participants in the JUPITER trial developed a DVT or PE, the reduction in the risk of a venous thromboembolic event among the participants who took rosuvastatin could have happened by chance. In this systematic review and meta-analysis of 29 RCTs of statins that collected information on many more venous thromboembolic events, the researchers test the hypothesis that statins substantially reduce the risk of such events. A systematic review uses predefined criteria to identify all the research on a given topic; a meta-analysis is a statistical approach that combines the results of several studies. What Did the Researchers Do and Find?: The researchers identified 22 RCTs (105,759 participants) that compared the effects of statins with control (dummy) tablets and seven (40,594 participants) that compared an intensive statin regimen with a standard regimen. They then obtained largely unpublished information about the venous thromboembolic events that occurred during these trials (about 1,000 DVTs and PEs) from the original investigators. In the trials of statin versus control, allocation to statin therapy did not significantly reduce the risk of venous thromboembolic events. Thus, although events occurred in 465 participants who were given statins (0.9% of the participants) and in 521 participants who were given control tablets (1% of the participants), this difference in outcomes was not statistically significant—it could have happened by chance. Exclusion of the JUPITER trial results from the meta-analysis did not alter this finding. The researchers also found no evidence that intensive statin therapy reduced the risk of venous thromboembolic events compared to standard therapy. What Do These Findings Mean?: The findings of this meta-analysis do not support the suggestion that statins, either at the standard dose or at higher doses, reduce the risk of venous thromboembolic events substantially among healthy adults. It is possible that the effect of statins has been underestimated in this meta-analysis because of missing data or because of some other source of bias. Furthermore, because the total number of events in this meta-analysis is still relatively modest, these findings do not rule out the possibility that statins may reduce the risk of venous thromboembolic events by up to about one-fifth in some or all individuals. Additional large RCTs are now needed to investigate whether statin treatment does in fact reduce the risk of venous thromboembolic events in adults and, if it does, whether all statins have a similar effect and whether statin treatment is beneficial in everyone or only in specific subgroups of people. Additional Information: Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001310. Date: 2012 Downloads: (external link) Related works: Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text Persistent link: https://EconPapers.repec.org/RePEc:plo:pmed00:1001310 DOI: 10.1371/journal.pmed.1001310 Access Statistics for this article More articles in PLOS Medicine from Public Library of Science |
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