Continuing the trend of ‘known knowns’ in medical reporting comes the following: CNN.com – Studies confirm risks of ‘economy class syndrome’ – Dec. 8, 2003.
Yes, the risk of DVT does increase with more than 8 hours of air travel, but most prominently in those with known risk factors for DVT.
In that study, 16 cases were detected among international passengers arriving at Spain’s Madrid-Barajas Airport from 1995 to 2000. All of them involved flights longer than six hours.
So, let’s not panic. They found 16 cases in 5 years. I’d bet more people had babies on planes in that time (though that’s a different risk factor).
Me, I drink water and I take an aspirin before I fly. Your mileage may vary.