People who do not have blood group O are at an increased risk of suffering a heart attack or stroke, according to new research.
Almost half (48 per cent) of people in the UK have O blood. But according to an analysis of studies involving 1.3million people, those who have A, B and AB blood have a slightly higher risk of heart disease and stroke.
Scientists think it could be because of higher levels of a blood-clotting protein in those blood groups.
Study author Tessa Kole, of the University Medical Center Groningen in the Netherlands, said blood group should be considered in the future as part of risk assessment in preventing cardiovascular disease.
Of those with blood group O, 14 in 1,000 people suffered a heart attack. For non-O blood groups, the figure was 15.
While the increased risk is small on an individual level, it could be important in terms of the population.
Charities say the most important thing to avoid heart disease is to eat healthily, stop smoking and take exercise.
Dr Mike Knapton, associate medical director at the British Heart Foundation, told the BBC: "Most of a person's risk estimation is determined by age, genetics (family history and ethnicity) and other modifiable risk factors including diet, weight, level of physical activity, smoking, blood pressure, cholesterol and diabetes.
"People with a non-O blood group type - AO, BO and AB - need to take the same steps as anyone wanting to reduce their CVD risk."
The research was presented at the European Society of Cardiology.