Contrary to the prevalent belief, smoking is the most important cause of premature heart attacks, with India having about 4.5 crore patients with ischemic heart disease, doctors warned on Wednesday on the eve of the “World No Tobacco Day.”

According to the World Health Organisation, tobacco use is one of the biggest public health threats worldwide which kills nearly six million people a year of whom about 600,000 are non-smokers exposed to second-hand smoke.