Patients with blood type O have lower levels of a clotting agent that helps prevent severe bleeding, say scientists.

Having type O blood can more than double the risk of dying from serious injuries, a study has found.

The blood group is associated with lower levels of a clotting agent which may result in greater bleeding, researchers believe.

Data from 901 emergency care patients in Japan showed a death rate of 28% for those with type O blood.

The death rate of patients from other blood groups combined was 11%.

Lead researcher Dr Wataru Takayama, from Tokyo Medical and Dental University Hospital, said: “Recent studies suggest that blood type O could be a potential risk factor for haemorrhage.

“Loss of blood is the leading cause of death in patients with severe trauma but studies on the association between different blood types and the risk of trauma death have been scarce.

“We wanted to test the hypothesis that trauma survival is affected by differences in blood types.”

Forty-seven per cent of the UK population are type O, making it the most common blood group.

Blood type is determined by proteins on the surfaces of red blood cells. The other main blood group categories are A, B and AB.

Type O blood can generally be donated to anyone with no ill-effects.

However, people with type O blood have lower levels of Von Willebrand factor, a blood clotting agent that may help prevent life-threatening bleeding.

Dr Takayama said the results raised questions about the emergency transfusion of type O red blood cells to severe trauma patients – victims of injuries with the potential to cause long-term disability or death.

All the study participants had suffered severe trauma and been admitted to critical care medical centres in Japan between 2013 and 2016.

The research is reported in the journal Critical Care.