Blood clots don't discriminate by fitness level. Hall of Famer Chris Bosh, now 42, spent a week in the hospital after suffering a pulmonary embolism in January 2026, nearly a decade after the same condition ended his NBA career. His case illustrates a puzzling paradox: elite athletes, the healthiest people in the country, keep developing blood clots at rates that seem to defy logic.

What Exactly Happens During a Pulmonary Embolism?

A pulmonary embolism occurs when a blood clot lodges in an artery carrying blood from the heart to the lungs, blocking oxygen flow to lung tissue. The clot usually forms first in a deep vein in the leg, a condition called deep vein thrombosis (DVT). Once it breaks loose and travels through the bloodstream, it can wedge in the lungs with devastating speed. Bosh described the onset as instantaneous: he was walking from his closet to the bathroom when he felt a numbing sensation shoot down his left leg, then lost consciousness.

When a clot blocks a lung artery, the right side of the heart must work harder against a suddenly closed pathway. If the blockage is large enough, that chamber can fail within minutes. The danger is compounded by the fact that sudden death is the first symptom in roughly 25% of pulmonary embolism cases, meaning a quarter of patients never get a chance to seek help.

Why Are Professional Athletes Uniquely Vulnerable?

The athletic lifestyle inadvertently creates perfect conditions for blood clots. Athletes fly constantly and sit immobile for hours during travel. They sweat off fluid volume, which thickens the blood. They absorb blunt trauma that injures blood vessel walls during competition and training. Then they sit still again while those injuries heal. This combination satisfies all three factors of what doctors call Virchow's triad: blood that clots too easily, blood that moves too slowly, and damaged vessel walls.

"Sitting on a plane for long periods of time or in a car without walking around can lead to venous stasis," said Dr. Benecia Williams, a double board-certified physical medicine and sports medicine physician at PMR Fort Worth. "Then a clot can form."

Dr. Benecia Williams, Physical Medicine and Sports Medicine Physician at PMR Fort Worth

The numbers back up this concern. A 2017 review identified 55 venous thromboembolism events across the NHL, MLB, NFL, and NBA between 1999 and 2016. The mean age at diagnosis was just 29.3 years, and athletes lost an average of 6.7 months of playing time. Seven never returned to professional sports. Players who had a pulmonary embolism rather than a leg clot alone missed the most time, averaging 10.8 months.

What Risk Factors Make Blood Clots More Likely?

Beyond the athletic lifestyle, several medical and lifestyle factors increase clot risk. The Centers for Disease Control and Prevention ties more than one-third of diagnosed cases each year to a recent hospital stay, with most clots surfacing after the patient goes home.

• Surgery and Hospitalization: Immobility during recovery creates ideal conditions for clot formation, which is why hospitals use preventive measures like anticoagulant medication and compression stockings.
• Serious Injury and Cancer Treatment: Both conditions trigger inflammatory responses and reduced mobility that increase clotting risk significantly.
• Pregnancy and Estrogen-Based Medications: Hormonal changes alter blood composition and vessel function, raising the likelihood of clot formation.
• Smoking, Obesity, and Chronic Conditions: These factors contribute to inflammation, high blood pressure, diabetes, and limited mobility, all of which increase clot risk.
• Inherited Clotting Disorders: Some people have genetic variations that make their blood clot more readily than average.

Race also plays a role, though researchers are still understanding why. One team following participants in the Atherosclerosis Risk in Communities study for more than two decades found crude incidence rates 65% higher among Black participants than white participants. However, a higher burden of underlying risk factors explained most of that gap, rather than race itself, meaning much of the difference is potentially modifiable through preventive care and lifestyle changes.

"Health outcomes are shaped by far more than genetics," said Dr. Dacia Russell Goman, a dual board-certified emergency and obesity medicine physician and founder of Apex Metabolic. "Obesity, high blood pressure, diabetes, limited mobility, chronic inflammation and barriers to preventive care all influence clot risk."

Dr. Dacia Russell Goman, Emergency and Obesity Medicine Physician at Apex Metabolic

How Serious Are the Long-Term Consequences?

The CDC estimates that venous thromboembolism affects up to 900,000 Americans each year, with between 60,000 and 100,000 deaths. Survivors face a longer recovery than most people expect. About one-third will have another clot within 10 years. A registry study tracking 896 patients for up to 14 years reported 1-year mortality of 19.7% and 5-year mortality of 37.1%, with cancer and cardiovascular disease driving much of that excess risk.

Two long-term complications deserve particular attention. Post-thrombotic syndrome causes chronic swelling, pain, and discoloration in the affected limb. Chronic thromboembolic pulmonary hypertension narrows the lung's blood vessels permanently and can prove fatal on its own.

Steps to Reduce Your Blood Clot Risk

• Disclose Your Medical History: Tell your doctor about hormone therapy, pregnancy, recent hospitalization, surgery, cancer, family history of clots, or prolonged travel, because these details determine whether preventive measures make sense during higher-risk periods.
• Ask About Prevention Before Leaving the Hospital: The CDC estimates that as many as 70% of healthcare-associated blood clots are preventable using anticoagulant medication and compression stockings, yet fewer than half of hospital patients receive them. Before discharge, ask the care team directly about a clot-prevention plan.
• Stay Mobile During Recovery: Even light walking keeps blood circulation working properly. The real danger arrives when an athlete or patient cannot bear weight on a limb at all, usually after surgery. Movement, even minimal movement, is protective.
• Manage Modifiable Risk Factors: Work with your doctor to address obesity, high blood pressure, diabetes, and smoking, as these conditions significantly increase clot risk and are within your control.

What Treatment Options Are Available?

Treatment for pulmonary embolism starts with anticoagulants, commonly called blood thinners. These drugs do not dissolve an existing clot. Instead, they stop it from growing and give the body time to break it down naturally. For severe cases with unstable blood pressure, doctors may add thrombolytic drugs to dissolve the blockage or remove it through a catheter-based procedure.

Duration of treatment varies. A clot provoked by surgery or a temporary injury may require only a few months of medication. However, an unprovoked or recurrent clot often means indefinite treatment. This is the situation Bosh faces: he must take blood thinners indefinitely to prevent another potentially fatal clot.

For athletes, blood thinners create a difficult professional dilemma. These medications prevent blood from clotting normally, raising concerns about brain bleeds if head-to-head contact occurs in contact sports. That collision of medicine and profession ultimately ended Bosh's Hall of Fame career. Spurs star Victor Wembanyama faced a version of the same calculation after a deep vein thrombosis cut short his 2024-25 season. Bosh's advice to him was blunt: "Take your medicine".

Bosh's experience underscores a critical lesson for everyone, not just athletes: listen to your body's warning signs. Sudden numbness, loss of consciousness, chest pain, or shortness of breath warrant an immediate emergency room visit. The difference between surviving a pulmonary embolism and becoming part of the 25% who experience sudden death often comes down to recognizing symptoms early and seeking help immediately.