Recent reported incidences of deep vein thrombosis (DVT) and pulmonary embolus (PE) in those who have travelled long distances have been the subject of an inquiry by the House of Lords Select Committee on Science and Technology (2000). The inquiry looked at evidence from groups that included physicians, researchers, travel industry representatives and members of the general public.
The inquiry examined predisposing factors for DVT and the general incidence of the problem. There is an increased clotting tendency in approximately 20% of the general population, possibly due to acquired or inherited metabolic, biochemical or blood abnormalities. These ‘naturally occurring’ DVTs happen at an average rate of roughly one case per 1000 people per year. For these individuals the risk of DVT is higher than for the general population; however, there are predisposing risk factors that affect us all.
The following should be aware that they may be at risk:
- Those aged over 40 with the risk increasing with age
- Pregnant women
- Patients with a history of, or a current, malignancy
- Those with an increased blood-clotting tendency
- Patients with cardiovascular insufficiency or disease
- Those who have a previous incidence of DVT or those with a family history of DVT
- Patients who have undergone recent surgery, particularly surgery to the abdomen or lower limbs
- People with an increased blood viscosity caused by dehydration
- Those who remain immobile for longer than 24 hours
- People with impaired blood-clotting mechanisms.
Varicose veins, obesity and smoking may also be predisposing risk factors for DVT, although the evidence for this is inconclusive.
The increased incidence of DVT, reported in the media, in those who have recently travelled by air was of particular concern to the inquiry. The inquiry urged the use of the term ‘travellers’ thrombosis’ instead of the more widely used ‘economy class syndrome’. It felt this term was misleading and that the condition should also be of concern to those travelling in business and first class.
The committee also concluded that the predisposing factors were present during any long period of confined travel, not just by air, but including journeys by road and rail. It urges all travellers to assess their own risk and to take appropriate action to minimise the likelihood of developing a DVT.
Risk factors for different groups of people relating to long-distance travel are listed in Box 1, with the recommended action to be taken.
House of Lords Select Committee on Science and Technology. (2000)Fifth Report (15 November). London: The Stationery Office.