Which of the following is a risk factor for developing deep vein thrombosis (DVT)?

Prolonged immobilization is a well-established risk factor for developing deep vein thrombosis (DVT) because it can lead to stasis of blood flow in the veins. When a person is immobile for extended periods, such as during long flights, post-surgical recovery, or bed rest due to illness, the normal flow of blood, especially in the lower extremities, is disrupted. This stagnation of blood increases the likelihood of clot formation.

DVT occurs when a clot forms in a deep vein, often in the legs, and can lead to serious complications if the clot dislodges and travels to the lungs, resulting in a pulmonary embolism. Recognizing prolonged immobilization as a risk factor highlights the importance of mobilization and prophylactic measures such as leg exercises and, sometimes, anticoagulation therapy in at-risk patients to help prevent DVT.

The other factors presented do not contribute to the risk of DVT. Frequent exercise promotes circulation and reduces the risk, while a low body mass index and adequate hydration are generally associated with a lower risk of thrombosis rather than an increased risk.