Most of us are aware of the worrying stories that began circulating in the media a few years ago about the dangers of developing life-threatening blood clots (deep vein thromboses, or DVTs) after taking long haul flights, especially when travelling economy class. DVT was even re-named ‘economy class syndrome’ as a result. Other health risks associated with lengthy flights soon began to emerge: respiratory infections, including influenza, pneumonia and even TB, caused by mixing fresh air with 50% recycled air (a practice, adopted by most airlines since the 1970s to reduce fuel costs). What are we to make of these stories? Just how serious a danger do we face when we take a long haul flight, especially if our work requires us to travel long distances on a long term basis?

A closer look at the stories – even those promulgated by apparently official bodies such as the UK’s Aviation Health Institute (established as a registered charity in 1996 to promote the health and well-being of air passengers) – might suggest that the best medicine to take in these circumstances is a generous pinch of salt. This isn’t to dismiss the stories as fictitious – some people undoubtedly have been taken ill with blood clots following long haul flights and have even died as a result. The human tragedy of stories like this is bound to affect anyone who reads them far more deeply than scanning through a list of statistics: we seem constitutionally hard-wired to respond emotionally, and sympathetically, to stories of personal adversity and misfortune than to columns of numbers. But whilst carefully conducted research has various claimed that the risks of DVT are doubled or even tripled with long haul flights, the incidence still remains very low.

It’s a fly, on Fly. Get it?!

All the studies show that it is prolonged inactivity rather than flying per se which increases the risk – something to be borne in mind by anyone (myself included) who sits for hours at a time tapping away at a computer keyboard on a regular basis. But to return to the issue of prevalence: the hospital closest to Heathrow Airport in the UK reported that it had seen 30 cases of DVT following long haul flights – out of 30 million passengers that had passed through the airport. Not all of these had been on a long flight, of course, but you begin to see that a sense of proportion is needed to avoid unnecessary panic. One New Zealand study concluded that the risk of DVT for long haul passengers did increase, and was roughly 1 in 100; clearly the more frequently you take long flights, the more ‘shakes of the dice’ you are performing in comparison with people who only fly occasionally. An American study basically confirmed these findings: by comparing long-haul passengers with a non-travelling control group (matched for age and gender), a similar figure of just under 1 in 100 was found, roughly twice that for people who had not flown. If you want to check them, both these studies are summarised in the March 2003 edition of the medical journal Pulmonary Reviews.

Are you willing to gamble?

Another health risk attached to long haul, long term flying which attracted media attention was the danger of exposure to increased levels of radiation (there is undoubtedly increased ionising radiation at high altitudes). The Financial Times ran a story in April 1999 revealing that passengers who fly from London to the east coast of the USA regularly, spending 700 hours a year in flight, could accumulate the equivalent of 170 chest X-rays in radiation, increasing the danger of cancerous cellular alterations. The more you fly, a source quoted in the report stated, the greater the risk. Again, whilst these facts about ionising radiation are true, we still might ask ourselves just how many people spend more than 700 hours a year at high altitudes, especially in an age when emails and video-conferencing are more convenient and vastly less expensive than air travel. And, of course, the more you simply live the greater the risk of something bad happening becomes; to become governed by risk aversion is, in the extreme, to become paralysed.

‘Mmm, X-Rays…’

None of this is to recommend a dismissive attitude. There are still sensible precautions to be taken to help reduce the risk of DVT: getting out of your seat as often as you can, walking around, stretching and drinking plenty of water remains sound medical advice. If you’re still a little anxious, invest in some compression stockings, too. If you are a high-risk passenger – someone who has either had a stroke or is at increased risk of one, or has a blood disorder – always take medical advice before embarking on a lengthy flight. The radiation issue is unavoidable – if you’re up there for any length of time, you’re going to get more irradiated than if you were down here. But provided you don’t come anywhere near the toxic 700 hours a year in flight (you’d probably glow in the dark if you did), and you use video-conferencing whenever it’s wisest to do so, you almost certainly have little to worry about. Vitamin C and E are good for mopping up free radicals released into your blood by any additional radiation, but try not to travel if you’re in the first three months of a pregnancy because the foetus is more vulnerable to the effects of radiation. Finally, stuffy air can trigger asthma attacks, if you’re prone to them, so make sure you’ve got your medication with you.

You may be more at risk of needlessly exaggerated worrying, or of becoming mind-numbingly bored, so keep a sense of proportion and make sure you’ve got a selection of entertainments with you, from music, a rattling good read, to crossword puzzles and, if they rock your boat, hand-held computer games (not during take-off and landing, of course).