About 1% of long-distance air travellers are likely to suffer symptoms caused by "economy class syndrome", new research suggested yesterday.

Scientists said the findings indicated that blood clots in the legs or lungs were a potential danger for many passengers, not just those at special risk.

The research also showed that deep vein thrombosis (DVT) or pulmonary embolism could strike people who tried to protect themselves against clots or flew business class.

"The term economy class syndrome should be avoided," said the scientists writing in the medical journal, the Lancet.

A previous study had suggested that symptomless DVT could occur in up to 10% of long-haul fliers.

The new research, by a team from New Zealand, assessed what proportion of passengers suffered actual ill-effects. All 878 participants travelled for at least 10 hours, each flying an average of 39 hours, during the six-week study. Seventeen per cent wore compression stockings; 31% took aspirin to reduce risk of thrombosis.

The researchers identified four cases of pulmonary embolism and five of DVT, amounting to 1% of the total.