British Asians are known to have a higher risk of heart disease
A gene mutation that almost guarantees the development of heart disease is carried by 60m people, researchers say.
Around 4% people from the Indian subcontinent have the mutation, which increases the risk of heart disease seven-fold, Nature Genetics reports.
It is rare to find a gene which has such a big effect and is so common, the international team of scientists said.
Experts said it could lead to a screening test but it was not yet clear if it would aid treatment decisions.
Heart disease is the number one killer in the world and India is particularly badly hit, with the problem set to intensify in coming years.
The World Health Organization estimates that by 2010, India will have 60% of the world's heart patients.
The researchers first identified the mutation in the heart protein gene MYBPC3 five years ago in two Indian families with cardiomyopathy - a disease causing deterioration of the heart muscle.
In the latest study they looked for the mutation in 800 people with heart disease and 700 controls.
They found the mutation was common - carried by 1% of the world's population.
And the increased risk of heart disease - seven times that of people without the mutation - is so high is almost guarantees the development of heart problems.
In the test tube, cells with the mutation - where 25 letters of genetic code are missing - the MYBPC3 protein is abnormal and "messes up" the structure of the heart muscle.
The researchers said in younger people the body seemed to have an effective mechanism for breaking down and removing the mutated protein.
But with age the mechanism stops working efficiently which is why heart disease in people carrying the gene develops in middle age.
Chris Tyler-Smith, a senior investigator at The Wellcome Trust Sanger Institute, Hinxton, UK, and one of the study authors said the mutation probably arose around 30,000 years ago and has been able to spread because its effects usually develop only after people have had their children.
"What we expect to find are common mutations with very small effects or rare mutations with big effects.
"The combination of big effects and high frequency is surprising."
He said "in principle" it would be extremely easy to test people at a young age for the gene but at the moment all that doctors could do would be to offer healthy lifestyle advice.
"In the longer term I think trying to improve the efficiency of the protein degradation mechanism might be a novel approach for treatment - all you would have to do is postpone the effects for a few decades."
Professor Peter Weissberg, medical director at the British Heart Foundation, said the study underpins the strong genetic nature of heart disease.
"It provides good grounds for screening people of South Asian origin with unexplained heart failure and screening their families if positive."
"However, there is no evidence yet that early detection will lead to improved outcome since we have no idea if the outlook for this group can be modified by conventional heart failure treatments."