Long-Haul Flights Double Risk of Blood Clots: WHO

GENEVA ~ Taking a long-haul flight doubles the risk of developing blood clots that can lead to potentially fatal deep vein thrombosis (DVT), the World Health Organisation (WHO) has warned.

DVT occurs when a clot forms in leg veins during periods of relative immobility, such as long-haul travel. The clot can then migrate to the lungs in what is called a pulmonary embolism, or the heart or brain, causing a heart attack or stroke.

The overall phenomenon is known as venous thromboembolism (VTE), the WHO said in its Research into Global Hazards of Travel project.

Following five separate research studies as part of first phase of the project, the WHO said that “the risk of developing venous thromboembolism approximately doubles after travel lasting four hours or more.”

The absolute risk of developing VTE if seated and immobile for more than four hours remains “relatively low,” at about one in 6,000, the WHO said.

However the chances are greater for people deemed at risk – for example those who regularly take long-haul flights, those who are obese, either very tall or very short (above 1.9 meters and below 1.6 meters), women who take oral contraception or people with inherited blood disorders, it said.

“There is a public health issue,” said Shanthi Mendis, a WHO senior adviser on cardiovascular diseases, noting that some two billion people are estimated to fly every year.

The WHO stressed that the risks posed by immobility do not just apply to airline passengers but also those who undertake long journeys by car, bus or train.

“The risk is linked to the fact the people are seated and do not move, they remain immobile for several hours … we don’t move enough when we travel,” Catherine Le Gales-Camus, WHO assistant director general for non-communicable diseases and mental health, said.

Travelers could take “common-sense” measures to reduce the risks of contracting VTE by regularly exercising their calf and ankle muscles during a journey, or simply getting up and moving around a bit, the WHO said.

Passengers should also avoid taking sedatives or too much alcohol ahead of a voyage, it added.

However, it shied away from making specific recommendations of preventive measures such as blood-thinning medications and elastic stockings that seek to prevent clotting, saying more research was needed into possible side effects.

“There is a clear need for travelers to be given appropriate information regarding the risks and for further studies to identify preventive measures,” which would be covered under the second phase of the research project, the WHO said.

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