I am going to be flying to Bangkok and Melbourne soon - two flights of nearly 12 hours each. Should I be wearing compression stockings?

Dr Fred Kavalier answers your health question:

A deep-vein thrombosis (DVT) is a blood clot that forms in a vein, often in the leg. The reason why DVTs form is complex, but one factor is immobility. Movement and exercise tighten the calf muscles, and this squeezes the veins of the leg and acts as a pump to keep the blood flowing. When blood flow slows down, a clot is more likely to form. These clots can then dislodge and shoot off towards the lungs. A big blood clot that travels to the lungs can be fatal. This is known as a pulmonary embolism. Compression stockings put graduated pressure on the legs to keep the veins squeezed relatively closed. This makes it less likely that a clot will form. In a combined analysis of research studies that included more than 2,500 long-haul passengers, DVTs were nearly 25 times more likely in people who did not wear stockings, compared with those who did wear them. The research was not able to say whether stockings can prevent fatal pulmonary embolisms, because none of the people who developed DVTs went on to collapse and die from embolisms. For flights lasting more than seven hours, stockings probably are a good idea. It's also important to drink plenty of non-alcoholic fluids (to prevent dehydration) and to take exercise by walking up and down the aisles and regularly wiggling your feet and ankles.

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.