Okay, it's the DVT Report. A couple of people might be interested in this.
Four years ago, I had a deep vein thrombosis (to be accurate, a subclavian-axillary vein thrombosis, for which air travel is not a major risk, tho there has been at least one medical journal article on the subject). Nevertheless, I took some precautions on the long-haul flights (i.e. international, not domestic). I wore 'TEDs' (can't remember what this stands for, but they're elasticised, knee-high stockings) and I took 'baby' aspirin (i.e. 100 mg) for ten days before the flight then when I remembered while I was in the US. I ran out on my last day, so I've just been taking fish oil capsules since then (Ok, Tjilpi: shut your eyes now).
Truth is, I think things like TEDs and aspirin are just magic talismans to ward off evil. As far as I can see from the studies I've read, the only thing that's truly effective in stopping DVT on long-haul flights is heparin, which comes out way ahead of aspirin and TEDs in studies (one study only found one superficial venous thrombosis in passengers who took heparin on long-haul flights as opposed to significantly more in those in the control group and those taking aspirin and wearing TEDs respectively). I'd happily inject myself with heparin and be done with it, but medical practitioners aren't keen on this for some reason (something to do with potential internal haemorrhaging -- and no, there's nothing to injecting yourself in a fat-fold. About as scary as digging out a splinter.)
I'm really cynical about the value of aspirin in preventing DVT (tho I'm cynical of many things, as regular readers will know). Personal agenda in not wanting to take aspirin: it's an annoying drug, even in its supposedly non-irritant coated form. If you mountainbike and take aspirin, you will end up looking like a victim of domestic violence (i.e. you'll be covered in bruises). My understanding of the medical literature is that aspirin will help in de-clagging platelets and preventing arterial thromboses and heart attacks, but it's not effective in unsticking the scaffolding stuff that makes up venous thromboses (heparin and warfarin are). If aspirin was that effective, they’d put you on it in hospital when you have a DVT, but they don’t: they put you on heparin. (They only tell you to take aspirin in A & E when they don’t know what else to do with you and are hoping that you, a healthy looking specimen after all, will just stop worrying and go away).
So, yeah, take aspirin and wear TEDs if you like (after all, I did) but really, I think adequate hydration and mobility are probably more important when it comes to air travel. People often quote this mystical thing about 'pressurised cabins' in planes and how it causes DVT. I'm not really sure how this is meant to be, unless it means lower oxygen levels (and things are getting pretty stuffy towards the end of a long-haul flight). Without 'pressurised cabins' having any magical properties, there are enougb risk factors already in air travel, like the cramped seating and associated immobility, and the lack of adequate hydration. A haematologist I saw after my DVT was likewise cynical about air travel being a significant cause and put it down to people drinking too many diuretics or women being on the Pill on flights.
Nevertheless, I was quite taken aback to find there was no more room in economy class on an international flight than there is on the plane that does the run up to Darwin. The plane is wider, but there is no more leg room than a domestic flight. The space you have is so tiny, I really doubt the miniscule exercises they suggest you do for 3-4 minutes on the hour in your seat (if you can stay awake that long) will have that much effect. You're much better off getting up and walking round the plane several times. United Airlines had an inspired upgrade to Economy Plus that you can do, which gives you about as much leg-room as the seats near the emergency exit on a Qantas flight. (All the African-Americans are down the back of the plane in the cramped economy seating, of course.)
And the there's the water thing -- not a word about adequate hydration in the Qantas magazine except that you should avoid drinking too much alcohol and caffeinated drinks. I flew on Qantas, United Airlines and American Airlines during my travels, and I took great interest in how difficult it was to get plain H2O on their flights. Water helps thin your blood and break down clots. Dr G&T told me that an active person in the desert should drink 4L of water per day to avoid DVT (yes, I really do drink that much); in a temperate region they should drink 2L. So, on a plane you would think that at least 2L would be the go.
I put an empty water bottle in my bag (with the intention of re-filling it on the plane) when I went through Sydney airport on my way to the States. Admittedly, it was a used bottle and there was some residue on its sides. Do you think they'd let me take it on board? No, it was confiscated, along with an old lipstick in my bag I'd forgotten about. (I think they just felt they needed to remove something, it being the weekend after the London terrorist threats, tho the same thing happened to me once on a domestic flight in the US.) On the other hand, out of the three airlines, Qantas probably came out on top in making water available on its flights. Not only did they offer those tiny plastic cups of water that wouldn't hydrate a flea several times on their flight; they handed out a 600 ml water bottle (which has to be a change from the 250 ml bottle you get on a domestic flight). American Airlines were suitably diligent in offering tiny cups of water several times on their flights. But United Airlines were crap. I asked for water twice on one of their flights; they said it would be around later and in the meantime, but brought two beers to the man beside me, (who became quite fascinated by my war for water: 'So they still haven't brought you any water?') In the end, I resorted to the water fountain at the back of the plane. I guess the magic factor here was that you don't have to pay for water. They later brought round some of those tiny cups...once. I didn't say anything about DVT; I was just interested to see what they would do. You could probably write an article, comparing different airlines to find out how difficult it is to get enough water on them.
The other thing to say is that air travel is not necessarily a major cause of DVT in itself. The factors that cause DVT are present in many other situations; it's just the recent hype attached to air travel that has publicised this disease. Personally, I'm more fearful of other causes of DVT, such as the (oestrogen) Pill, than I am of air travel. Walk around, drink lots of water on planes, is all I've got to say. (I drank coffee and some alcohol.) As far as I know, I don't have a DVT (and the feel of one is distinctive enough, if nothing else: your limb feels 'like a plank with a nail through it' as one chatroomer said.)
But I must have been concerned enough to write such a lengthy post on the subject.