Which of the following is a risk factor for pulmonary embolism?

• A. Regular exercise
• B. Smoking
• C. Prolonged immobility
• D. Low-fat diet

Answer: (C)

Prolonged immobility promotes venous stasis, a key trigger for clot formation in the deep veins. When a clot forms in these veins, it can break loose and travel through the bloodstream to the lungs, where it blocks branches of the pulmonary artery—this is a pulmonary embolism. So this factor directly increases the likelihood of a clot forming and then embolizing to the lungs.

Regular exercise tends to improve venous return and reduce stasis, lowering the risk of PE. A low-fat diet doesn’t have a direct, established link to clot formation, and while smoking is a risk factor for many cardiovascular conditions, it is not as direct or as strong a contributor to venous thromboembolism as immobility-induced stasis.