Expert Evidence To House Of Lords Committee States Aspirin Of Doubtful Value To Prevent DVT

Main Category: Cardiovascular / Cardiology
Also Included In: Public Health
Article Date: 27 Dec 2007 - 1:00 PDT

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A University of Leicester academic has given evidence to the House of Lords' Science and Technology Committee.

Dr William Toff, Senior Lecturer in Cardiology, gave expert evidence to the inquiry on Air Travel and Health. He told the committee that, "for the average traveller, the use of aspirin is a relatively ineffective intervention" in the prevention of DVT. Whilst it undoubtely has a role in reducing the risk of arterial thrombosis it has only a modest effect in the prevention of venous thrombosis. Indeed, in some cases the use of aspirin may be counterproductive.

Dr Toff went on to say that "you have to treat a lot of people to prevent one thrombosis and the estimate would be something in the region of treating 24,000 people to prevent one thrombosis. On the other hand, the number that you need to treat for harm from aspirin is in the region of one in 17,000" . In other words, on the balance of probabilities, and for the population as a whole, taking aspirin as prophylaxis may be more likely to do harm than good.

Dr Toff is a member of the Scientific Executive Committee responsible for the design and implementation of the WRIGHT project into the health risks of long haul flights.

His team also led the studies to investigate the possible effects of low pressure and low oxygen in the aeroplane cabin on the risk of thrombosis. The research found no evidence of such effects.

Dr Toff said: "The first phase of the WRIGHT Project has improved our understanding of the scale of the problem of travellers' thrombosis and its underlying causes. For most people, the risk is very low but they should regularly exercise their legs when seated for prolonged periods and get up or interrupt long journeys to take a walk from time to time. That applies not just to air travel but to long journeys by car, bus or train. For people with known risk factors for thrombosis, the risk from long-distance travel may be much greater and they should discuss the need for other preventive measures with their doctor."

The study did not investigate effective preventive measures against DVT and VTE. However, experts recognize that blood circulation can be promoted by exercising the calf muscles with up-and-down movements of the feet at the ankle joints. Moving the feet in this manner encourages blood flow in the calf muscle veins, thus reducing blood stagnation. People should also avoid wearing tight clothing during travel, as such garments may restrict blood flow.

Phase I of the WRIGHT project concludes that there is a need for travellers to be given appropriate information regarding the risk of VTE by transport authorities, airlines, and medical professionals. Further studies are needed to identify effective preventive measures. This will comprise Phase II of the project, which requires additional funding before it can begin.

Individuals with questions regarding prevention of VTE should consult their physicians before travelling.

Background on the WRIGHT project:

In 2000, media and public attention was focused on the risk of thrombosis in long-haul travellers, following the death from pulmonary embolism of a young English woman who returned on a long-haul flight from Australia. In the same year, a report from the Select Committee on Science and Technology of the United Kingdom House of Lords recommended research into the risk of DVT. Following a consultation of experts convened by WHO in March 2001, the WRIGHT Project was initiated. Phase 1 was funded by the UK Government (Department for Transport and Department of Health) and the European Commission.

The objectives of Phase I were to confirm whether the risk of venous thromboembolism (VTE) is increased by air travel and to determine the magnitude of risk.

The studies were conducted under the auspices of WHO and performed by an international collaboration of researchers from the Universities of Leiden, Amsterdam, Leicester, Newcastle, Aberdeen and Lausanne. There were five studies: a population based case control study to investigate the risk factors of VTE; two retrospective cohort studies among employees of international organizations and Dutch commercial pilots to investigate the actual risk of VTE related to air travel; two pathophysiological studies to investigate the influence of immobility on VTE related to travel and the influence if any of low oxygen and low pressure in the cabin of air crafts on VTE related to travel.

University of Leicester
http://www.le.ac.uk