Fear of flying linked to higher risk of blood clots

By SCOTT MacLEOD and REUTERS

Deadly blood clots that develop in the veins of air travellers may be caused by fear of flying and the stress of getting to the aircraft, a British researcher says.

Peter Hughes says fear and stress could be the main cause of deep vein thrombosis (DVT), or economy-class syndrome.

He says stress makes adrenaline surge through the human body, squeezing the veins and making clots more likely.

A leading New Zealand travel clot researcher says he doubts the theory because there are few muscles around veins to make them constrict.

And a NZ specialist in the fear of flying says scared people may get clots because they sit bolt still on aircraft and take immobilising drugs - but not because of adrenaline.

Most theories on travel clotting give cramped seating, immobility and low oxygen levels as the likely causes.

But Mr Hughes, who was supported by a panel of five leading doctors when he outlined his theory in London this week, said that a large percentage of air travellers were scared of flying and their fear was heightened by dealing with traffic jams, airport queues and security before boarding their aircraft.

On board, they were loaded into cramped seats, where they sat still so that blood could pool in their legs.

The stress of takeoff caused a "very high secretion of adrenaline, resulting in the constriction of the venous blood supply".

Doctors in Britain who have studied the problem estimate that 2000 people a year die from flight-related DVT and calculate that 10 per cent of travellers on long-haul flights could be at risk. No comparable studies have yet been done in New Zealand.

But Dr Rodney Hughes of Green Lane Hospital, who is testing 1000 travellers for blood clots, says muscles are necessary to make blood vessels constrict. Veins, which take blood to the heart, do not have muscles around them.

Dr Hughes says many of the 1000 people he tested flying overseas were stressed and yet did not develop clots. Two people with travel clots have telephoned him to complain about the theory because they felt it did not cause their condition.

"I'm not saying it's impossible, but I think it's unlikely," Dr Hughes says of the theory.

Grant Amos, who directs an independent programme called Flying Without Fear, says he doubts there is a link between fear, adrenaline and clots.

But he says anxious people tend to sit still on aircraft, which increases their risk of clotting, and many doctors give them valium, sleeping pills and other drugs that make them less mobile.

Feature: Economy class syndrome

nzherald.co.nz/health