Why Does Travel Increase the Risk of DVT?

Sitting still for long periods of time causes blood to pool in your legs.

It’s often dubbed Economy Class syndrome because of cramped conditions, but the idea is misleading.

Dr Brewer said: “The problem isn’t just confined to Economy Class, or to long haul flights.

Stabbing chest pain, a rapid heart beat, shortness of breath and collapsing are all signs of a pulmonary embolism and it’s vital to dial 999 immediately

“People flying in Business and First class – even on flying beds – have also been affected, and some deaths have been linked with short haul flights.”

While inactivity and cramped spaces are a major risk, there are other things about flying that increase your risk of DVT.

“Reduced oxygen saturation in the cabin, dehydration and reduced cabin pressure cause fluid to leak from the circulation into the lower legs, causing swelling,” Dr Brewer explained.

And she warned it’s not just travellers who fly who are at risk.

Symptoms such as stabbing chest pain and shortness of breath may not happen for several days, even weeks after the DVT initially formed

Dr Sarah Brewer, Medical Director Of Healthspan

“Any long distance journey lasting four hours or more doubles your risk of a venous thrombosis, however you travel – whether by plane, car, coach or train,” she added.

Studies suggest flying still presents the greatest risk.

Evidence has shown the risk of DVT is quadrupled for plane passengers, with longer flights proving more dangerous.

On flights shorter than four hours, the risk of DVT is low – happening once every 106,667 flights.

But on longer haul trips that risk soars to one ever 4,656 flights – reaching one every 1,264 flights for those journeys over 16 hours.

Who is at greatest risk?

Certain things increase your risk of DVT, including taking the oral contraceptive pill. In most cases your risk will be low, but it’s important to know what increases your risk.

Dr Brewer said: “Many women don’t realise, for example, that if you board while taking HRT or the contraceptive pill your risk of travel thrombosis is significantly increased. “This is because the hormone oestrogen increases blood stickiness.” And very tall people – those over 6ft 2ins – and very short people – under 5ft 2ins – are also at greater risk. Dr Brewer explained: “If you are short, the back of the seat will press more against the back of your legs. “While if you are very tall, blood has to flow further through the veins and is more likely to become sluggish.”

You’re at high risk if:

  • you’ve had surgery in the four weeks before you fly – if you were under general anaesthetic for more than 30 minutes
  • you have a blood clotting disorder, such as thrombophilia
  • you have cancer – whether untreated or currently on treatment

You’re at moderate risk if you:

  • have a previous history of DVT or pulmonary embolism – though if you’re on anticoagulant treatment the risk is low
  • smoke – it makes the blood stickier
  • have had an operation in the two months before you fly – if you were under general anaesthetic for more than 30 minutes
  • are pregnant or recently had a baby
  • have recently had a heart attack, or illness like pneumonia
  • are taking the combined oral contraceptive pill or hormone replacement therapy (HRT)
  • are obese
  • have varicose veins – with inflammation of the veins, known as phlebitis
  • have a family history of DVT or pulmonary embolism in a first relative – mum, dad, brother or sister
  • have a broken lower limb that’s still in plaster
  • have a condition called polycythaemia – which causes you to make more red blood cells than normal

The more of these risk factors you have, the greater your risk of DVT.

Dr Brewer warned: “Being overweight doubles the risk of thrombosis, but in women who are both overweight and take the oral contraceptive pill, the risk increases tenfold.”