Study Finds Continuing Blood Thinners After a Clot Greatly Reduces Risk of Recurrence and Death

A large national study has found that people who continue taking oral blood thinners after an unprovoked blood clot are far less likely to suffer another clot or die prematurely compared with those who stop treatment after 90 days.

Based on more than 60,000 patients, the study, titled “Continued versus discontinued oral anticoagulant treatment for unprovoked venous thromboembolism: target trial emulation,” published in The BMJ, found that extended use of anticoagulants reduces the risk of a repeat venous thromboembolism. Thromboembolism is a condition that encompasses deep vein thrombosis, a blood clot in the leg, and pulmonary embolism, a clot that travels to the lungs. Together, these conditions affect about 1.2 million people in the U.S. each year and carry a one-year mortality rate of roughly 20%.

Using national insurance and Medicare data, researchers compared adults who continued blood thinner treatment for at least 90 days after a first unprovoked clot with those who stopped treatment.

Patients who continued taking anticoagulants had:

• An 81% lower risk of another blood clot (hazard ratio 0.19)
• A 26% lower risk of death (hazard ratio 0.74)
• A 75% higher risk of major bleeding, most commonly in patients on warfarin

Despite the increase in bleeding, the overall “net clinical benefit” — a combined measure of clotting and bleeding events — strongly favored continuing therapy. These findings held true across all types of oral anticoagulants, including newer agents such as apixaban and rivaroxaban, and for patients who had been on therapy for up to three years.

“For patients who’ve had an unprovoked clot, continuing blood thinners after the initial 90 days can significantly lower the chances of another life-threatening event,” said Dae Hyun Kim, MD, MPH, ScD, associate director and senior scientist at the Hinda and Arthur Marcus Institute for Aging Research. “Although bleeding risk is real, our findings show that the benefits of ongoing treatment often outweigh the harms, especially with newer medications that carry lower bleeding risks.”

Venous thromboembolism is a leading cause of preventable hospital deaths in the United States. Standard medical practice recommends three to six months of anticoagulation after a clot, but data on longer-term outcomes have been limited, especially among older and medically complex patients. This study, one of the largest and longest to date, provides strong real-world evidence that extended anticoagulation offers substantial, sustained protection.

In addition to Kim, researchers included Kueiyu Joshua Lin, MD, ScD, MPH, associate professor of medicine, Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School; Daniel E. Singer, MD, professor of medicine, Division of General Internal Medicine, Department of Medicine, Massachusetts General Hospital and Harvard Medical School; Yichi Zhang, MS, research specialist, Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women’s Hospital; Alexander Cervone, BS, senior research assistant, Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women’s Hospital; Anna R. Kehoe, MS, clinical research assistant, Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women’s Hospital; and Katsiaryna Bykov, PharmD, ScD, associate professor of medicine, Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women’s Hospital and Harvard Medical School.

About Hebrew SeniorLife
Hebrew SeniorLife, an affiliate of Harvard Medical School, is a national senior services leader uniquely dedicated to rethinking, researching, and redefining the possibilities of aging. Hebrew SeniorLife cares for more than 4,500 seniors a day across seven campuses throughout Greater Boston. Locations include: Hebrew Rehabilitation Center-Boston and Hebrew Rehabilitation Center-NewBridge in Dedham; NewBridge on the Charles, Dedham; Orchard Cove, Canton; Simon C. Fireman Community, Randolph; Center Communities of Brookline, Brookline; Jack Satter House, Revere; and Leyland Community, Dorchester. Founded in 1903, Hebrew SeniorLife also conducts influential research into aging at the Hinda and Arthur Marcus Institute for Aging Research, which has a portfolio of more than $87 million, making it one of the largest gerontological research facilities in the U.S. in a clinical setting. It also trains more than 500 geriatric care providers each year. For more information about Hebrew SeniorLife, follow us on our blog, Facebook, Instagram, Threads, and LinkedIn.

About the Hinda and Arthur Marcus Institute for Aging Research
Scientists at the Marcus Institute seek to transform the human experience of aging by conducting research that will ensure a life of health, dignity, and productivity into advanced age. The Marcus Institute carries out rigorous studies that discover the mechanisms of age-related disease and disability; lead to the prevention, treatment, and cure of disease; advance the standard of care for older people; and inform public decision-making.