The term ‘economic class syndrome’ was coined by Cruickshank and associates in the journal Lancet in 1988, describing an increased risk of deep vein thrombosis in the legs after a prolonged episode of air travel. It was suggested to be more common in the economy class due to its cramped quarters and the difficulty in frequent ambulation.
Subsequent studies have confirmed the increased risk for deep vein thrombosis with frequent and prolonged air travel. Pooled data from 3 studies reveal that the relative risk for DVT is 26% higher for each 2-hour increment of flight duration.
It is estimated that about 2 billion people travel by air each year. With the advent of long haul flights, travelers are often sitting for long periods of time. According to scientific studies, oral contraceptives, sitting in a window seat, advanced age and pregnancy increases DVT risk in long-distance travelers. The risk also appears to be higher in short people (<165 cm) or tall people (>185 cm), and those that are obese (BMI over 25 kg/m2).
Formation of a blood clot in the deep veins of the legs is commonly known as deep vein thrombosis or DVT. This can be symptomless or may result in pain, swelling, redness and warmth in the affected extremity. DVT is dangerous as the blood clot can dislodge and travel to the lung resulting in a serious medical emergency called pulmonary embolism or PE. PE can be fatal. Trauma, prolonged inactivity and conditions such as cancer, infections, and certain inflammatory and cardiovascular diseases increase the propensity to develop DVT.
Travelers can take some precautions to decrease the risk of DVT:
- Stand, stretch and walk around the cabin every 2 hours.
- Keep well hydrated. This includes limiting alcohol and coffee intake.
- Wear loose clothing, especially from the waist down.
- Perform foot, ankle and knee exercises (flex and extend) while sitting, every hour or so.
- Walk at the airport during layovers.
People at high risk should also get professional compression stockings (providing 15-30 mm Hg pressure) or get one dose of low molecular weight heparin prior to a flight longer than 8 hours. Aspirin has shown no benefit in preventing deep vein thrombosis.