Thrombosis risk when flying

Thrombosis risk when flying – much ado about nothing or a present hazard?

Martina Roters
04.05.2020
5 minutes

At the turn of the century, physicians were still grappling with the mysterious causes of young people dropping dead in hospitals – whether they were soldiers who had been holding out in the trenches or women who had recently given birth. Thanks to the advancements in modern medicine, we can nowadays tap into knowledge on the causes of deep vein thrombosis (DVT) and therapies of treating such.

DVT crops up in the headlines time and again when it comes to flying: ‘travel thrombosis’, ‘flight thrombosis’, ‘aircraft thrombosis’ or even ‘economy class syndrome’.

Let us firstly take a look at exactly what this is.

What is thrombosis?

‘Thrombosis’ refers to the formation of a blood clot (thrombos = Greek for ‘clump’) in circulation, preventing unimpaired flow of blood. This occurs very frequently in the veins in the legs. Thromboses sometimes remain undetected, whereas in other cases the affected area becomes red and swollen. Blood clotting serves to save lives when people injure themselves. However, this clotting may become life threatening when it comes to a thrombosis, namely in cases where such a thrombosis frees itself and enters the pulmonary circulation. It is worth noting that tens of thousands of people die in Germany each year from pulmonary embolisms.

Thrombosis
Thrombosis in the leg

What are the reasons for a thrombosis?

There are three fundamental causes:

Composition of blood

The blood’s make-up may be significantly altered if someone ingests certain substances or by lack of fluids, illness or pregnancy.

Flow rate of blood

This is affected by either squashing of the blood vessels or a general lack of exercise – whether this is enforced or voluntary.

Composition of the internal vessel walls

As people grow older, the elasticity and smoothness of the vessel walls decrease; they are also impaired of course by illnesses (diabetes, phlebitis, tumours) or injuries (including operations), not to mention smoking.

Blood - Artery
Illustration of white and red blood cells / © Pixabay Vector8DIY 4769605

What are the greatest thrombosis risk factors?

High thrombosis risk:

The people exposed to the greatest risk are those with a history of thrombosis.

Even once an operation or injury is over, people are still exposed to a heightened risk of thrombosis for a certain period. It is no coincidence that thrombosis injections are carried out in hospital – and in some cases also for home use subsequently.

Cancer patients are significantly endangered too; their risk of thrombosis is 4 to 6 times greater than among the healthy. Thrombosis is the second most common cause of death for this group! It seems that the blood generally becomes more clotted. In some cases, tumour tissue also grows into a blood vessel or compresses such when it grows rampantly. Some doctors in fact see thromboses as ‘tumour markers’. If you receive chemotherapy, you may see your blood vessel walls damaged by the medication; the dying tumour cells in the blood stream may also lead to increased blood clotting.

Medium risk of thrombosis:

It is almost self-evident that people with heart disease are also more susceptible to sustaining a thrombosis. The same applies to pregnant women and women taking hormone products.

Even after having given birth, the risk of thrombosis is still somewhat higher for a certain period; this applies not only to women who delivered by Caesarean section. It seems that changes to hormones generally have a negative effect on blood clotting.

Smokers ought to be aware that they are damaging their blood vessels and therefore have a greater risk of thrombosis.

In terms of overweight people, the link may not be so cut and dried, as even doctors are still not able to explain the mechanism for increased risk of thrombosis exactly.

If you suffer from varicose veins, you will probably already be familiar with compression socks. Varicose veins are indeed a visible indicator for an increased backlog of blood.

In exactly the same way that working sitting down promotes varicose veins, it goes without saying that immobilisation also pushes up the risk.

Last but not least, a somewhat strange fact: people with a height above 1.90 metres (approx. 6’ 3”) also suffer thromboses slightly more frequently – irrespective of other risk factors. The reason for this is unclear; a possible reason would be that tall people simply have a much greater surface area of blood vessel interior walls on which a thrombosis can arise.

How great is the thrombosis risk today anyway?

It is evidently a difficult task to evaluate the risk, as studies on the subject matter reach some very contradictory results. Fortunately, these contradictions prompted some experts to conduct a meta study. In the process, they established that the results depended significantly on how the control group was selected. In their conclusion, they find as a genuine assumption that the risk of venous thromboembolism (VTE) is almost tripled on long journeys.

The risk increases by 26 per cent for every two hours that the flight lasts.
Expressed in absolute numbers: 1 case per almost 6,000 flights.

As a rule of thumb, it can be said that healthy people do not need to fear a thrombosis. On the other hand, those with one or even multiple risk factors would be well advised to take some preventative measures.

Do you need to speak to your doctor before travel?

People with risk factors (see above) should pay attention. Particularly in cases where multiple risk factors congregate, it is of course better to be safe than sorry. The probability of suffering a thrombosis here is significant, after all. Here are some fictitious scenarios:

Such people need to speak to their doctor before travel. In individual cases, doctors may prescribe a preventative medication and/or recommend wearing thrombosis socks. Experts advise against self-medication with Aspirin (acetylsalicylic acid).

What can you do to combat a travel thrombosis?

Even during travel, you can still take preventative steps:

And the most important of all: it does not matter how exciting a book or invigorating a film is, always keep moving your legs!

You can find inspiration here in this video with rhythmic exercises you can perform sitting down to mobilise the muscle pump. These can be practised behind a desk at home, meaning that you will know what to do on the plane …

While we are on the subject of health, you may find our article ‘The cold after flying’ of interest.

by Martina Roters

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