Study to look at deep vein thrombosis (DVT) and air travel
12 February 2001
A definitive study into the suspected association between deep vein thrombosis (DVT) and air travel will begin soon, following a roundtable held in Sydney of university aviation specialists, pilots and cabin crew associations, medical practitioners and airline representatives.
Griffith University has announced it will conduct the study, in conjunction with the Australasian Society of Thrombosis and Haemostasis (ASTH).
The next step will be to design the large-scale, case-control study, which will, in the first instance, focus on cases in Australia.
A case-control study is one which identifies people with the disease of interest (the cases)–here DVT–and then compares them with a similar group without the disease (the controls).
‘The reason we are concentrating on Australia is that we are a large island nation and therefore we are the people who travel on long-haul flights to get to US and European centres,’ Griffith’s Centre for Aviation Medicine and Human Factors Research Director Paul Bates said.
‘There is no doubt such a study would be of world significance,’ said Dr Bates.
‘Our first priority now is to ensure that the research logistics and resourcing of the project are in place so that we can commence work.
‘The greater the resourcing, the faster we can complete the research,’ added Dr Bates.
Outcomes of the roundtable
Following the meeting, further information and recommendations were released. The specialists said that there were a number of individual risk factors that increased the likelihood of someone developing a deep vein thrombosis (DVT), whether they were undertaking air travel, or not. These included:
- increasing age;
- lower limb injury or surgery;
- obesity;
- pregnancy;
- oral contraception or hormone replacement therapy;
- a previous or family history of DVT; and
- a previous pulmonary embolism.
The meeting also heard that recent studies published indicated that the incidence of travel-related DVT appeared small at an estimated one person in 2 million at ‘low risk’ and one event for every 100,000 passenger arrivals in ‘high risk’ individuals.
It was stressed that having one or even 2 risk factors is common, with the majority in this ‘low risk’ category not developing DVT. Those at ‘higher risk’ usually have numerous risk factors.
Preventing DVT
The meeting then highlighted a number of suggestions for inclusion in recommendations.
- Drink plenty of fluids.
- Regularly move ankles and massage your calves.
- Excessive movement around the aircraft during the flight is not recommended. It was thought that the risk of injury through unexpected air turbulence outweighed any additional benefit of the exercise.
- Information on the risk factors and symptoms of DVT should be made widely available, so people who are planning to fly are better informed and able to recognise potential problems or know to consult their doctor before flying. People should be vigilant for up to a month after air travel.
- Doctors should be kept informed about the latest information on risk assessment and subsequent management strategies for the prevention of travel-related DVT.
The role of aspirin in combating DVT was also discussed and it was said that while aspirin played an important role in the prevention of heart attack and stroke, there was still some uncertainty about its efficacy in venous disease. At best, it may have a weak protective effect. However, indiscriminate use by all travellers could cause unexpected problems including bleeding in the gut.
Also discussed was the routine screening for blood-clotting factors in people without a personal or family history of DVT. However, the specialists decided that this was not recommended. They said that these abnormalities were common in the healthy population (5-7 per cent) and most people with these blood abnormalities would not develop DVT in their lifetime.
Last Reviewed: 16 February 2001
