I Kid - your point is well taken. As I read it your post implies a question - if DVT/PE is such a dreadful danger how come I(you) have not noticed my mates dropping dead like flies after long trips?
Crashdive has "known pilots from both long and short haul for many a moon" and not noticed anything alarming.
If the syndrome IS real, then either you and Crashdive are remarkably unobservant or there is something different about pilots (yes
I know there is but we won't go into that here).
Code Blue - through much of these DVT threads runs a suspicion that DVT/PE is a megamega problem the extent of which is being wilfully withheld from the public by Skip Undo's "..members of the medical profession who are in the pockets of large corporations - and especially airlines".
All that I can say is that long-haul flights have been going on for many many years and while you can conceal an elephant for a while it tends to make it's presence felt fairly soon, whether you like it or not. A mouse, on the other hand, may go un-noticed for years.
Postal surveys do indeed have a low response rate - that is why I suggested the airmiles bribe - but even 12% of 100 million pax/year would be a sizeable sample.
We don't have to be perfect methodologically first time round. Just get the big picture - 10,0000 pax and 10,0000 nonpax - any excess events. If none, then forget it. If yes then by all means start looking more closely at smokers/pill/etc.
As for the DVTs, we are not talking about picking up silent events - just the clinically obvious to start with. You were not suggesting subjecting all disembarking pax/crew to ascending venography were you? No, most people with symptomatic DVTs will end up (in the first world) in hospital, on heparin and probably have some kind of confirmatory investigation. The investigations will have already been done and the data is there.
Grandad Flyer's suggestion is excellent and 20,000 PPRuNers would be an immediate though imperfect sample to checkout (have mercy on us cry Danny's servers....) At least we could get some idea what size animal is in the room with us!