Neck-vein thrombosis during spaceflight.

Spaceflight imposes unique environmental challenges, including weightlessness, increased radiation exposure and confinement, which can lead to unexpected health effects. One such example is neck-vein thrombosis, a condition rarely seen on Earth without predisposing factors such as venous catheters or infections. Although spaceflight has not previously been associated with thromboembolic events, recent cases of neck-vein thrombosis in astronauts aboard the International Space Station have raised concern. These events were detected incidentally and showed no obvious symptoms, complicating diagnosis. Retrospective studies have not found consistent biomarkers indicating a hypercoagulable state in space, but environmental factors such as weightlessness-induced venous stasis and potential endothelial damage may contribute. Oral contraceptives could promote thrombotic risk in female astronauts, although no direct link has been confirmed. Research on terrestrial models simulating space conditions has not yet provided conclusive insights into thrombosis prevention. Given the challenges in diagnosing and treating thrombosis in space, agencies such as National Aeronautics and Space Administration and European Space Agency have implemented surveillance programmes and recommended risk-mitigation strategies, including careful management of venous flow abnormalities and cautious use of anticoagulants. However, more research is needed to refine these strategies and improve safety in future deep space missions.