A team of researchers have revealed that taking long-haul flights nearly triples the risk of developing deep vein thrombosis (DVT), a blood clot that forms within a vein.
The study conducted by colleagues from Leiden University Medical Center, Academic Medical Center Amsterdam and Nestlé Medical Services has revealed that on average an air passenger who takes a flight lasting longer than four hours has a one in around 4,700 chance of getting DVT.
A survey of more than 87000 people also found that being tall, female, and overweight increased the risk of developing DVT.
Passengers who were overweight also had more than twice the risk of getting a clot on a long haul flight.
Women taking the contraceptive pill significantly had three times the risk of developing DVT.
However the researchers also found women were approximately twice as likely to get DVT after flying.
The researchers asked participants if they had suffered from DVT and about their risk factors for the condition.
They found that of the 53 clots identified in the study 22 occurred within eight weeks of a long-haul flight.
From this they calculated that one clot occurred for every 4,656 long haul flights taken.
Doctors suggested that people travelling on long haul flights should stretch their legs, take walks in the aisles and take plenty of water.
"The results of our study do not justify the use of potentially dangerous prophylaxis [treatment to prevent disease] such as anticoagulant therapy for all long haul air travellers, since this may do more harm than good," the Telegraph quoted lead researcher, Professor Frits Rosendaal as saying.
"However for some subgroups of people with a highly increased risk, the risk-benefit ration may favour the use of such prophylactic measures," Prof Rosendaal added.