Daily use of e-cigarettes combined with traditional smoking can lead to a five-fold increase in the odds of heart attack, according to study which also found that vaping alone doubles the risk. The study, published in the American Journal of Preventive Medicine, examined the relationship between e-cigarette use and heart attacks, and begins to fill the understanding of the effects of e-cigarettes on long-term health. "Most adults who use e-cigarettes continue to smoke cigarettes," said senior author Stanton Glantz, a professor at University of California - San Francisco in the US. "While people may think they are reducing their health risks, we found that the heart attack risk of e-cigarettes adds to the risk of smoking cigarettes," Glantz said. "Using both products at the same time is worse than using either one separately. Someone who continues to smoke daily while using e-cigarettes daily increases the odds of a heart attack by a factor of five," he said. The research found that dual use of e-cigarettes and conventional cigarettes - the most common use pattern among e-cigarette users - appears to be more dangerous than using either product alone. The risks compound, so that daily use of both e-cigarettes and conventional cigarettes raises the heart attack risk five-fold when compared to people who don't use either product. Researchers report some good news if smokers quit. "The risk of heart attack starts to drop immediately after you stop smoking. Our results suggest the same is true when they stop using e-cigarettes," said Glantz. Electronic cigarettes typically deliver an aerosol of nicotine and other flavours by heating a liquid and are promoted as a safer alternative to conventional cigarettes, which generate the nicotine aerosol by burning tobacco. While e-cigarettes deliver lower levels of carcinogens than conventional cigarettes, they deliver both ultrafine particles - which are 1\/50 to 1\/100 the size of a human hair - and other toxins that have been linked to increased cardiovascular and non-cancer lung disease risks. The analysis involved 69,452 people who were asked whether they had ever used e-cigarettes and\/or cigarettes, and whether they had ever been told by a doctor or other health professional that they had had a heart attack. Among the 9,352 current and former e-cigarette users, 333 (3.6 per cent) had experienced a heart attack at some point, with the highest percentage (6.1 per cent) among those who used e-cigarettes daily. In the analysis, a quarter of the 2,259 people who currently used e-cigarettes were former smokers of conventional cigarettes and about 66 per cent of current e-cigarette users were also current cigarette smokers. The researchers found that the total odds of having a heart attack were about the same for those who continued to smoke cigarettes daily as those who switched to daily e-cigarette use.