Sleeping pills can increase the risk of heart attacks by up to 50 percent, suggests US study.
Scientists found that zolpidem, which is sold under the brand name Stilnoct in the UK, is linked with a dramatic rise in the number of life-threatening cardiac events, the Daily Express reported.
Four standard dose pills a year - 35 milligrams - send the risk soaring by around 20 percent.
People taking the equivalent of 60 tablets a year could see the threat jump by half.
The study - presented to the world's biggest cardiology conference - is the first to connect the drug with cardiovascular problems.
Scientists cannot be fully certain yet that sleeping pills are causing heart problems - and the manufacturers say there are no known adverse cardiac reactions to zolpidem.
However, the researchers say the results from a study of more than 5,000 people are sufficiently worrying for "further large-scale and in-depth investigations".