In the decade since they first went on sale, e-cigarettes have been touted as a safer alternative to traditional cigarettes. But, research on the health impacts of e-cigarette use, presented at the annual meeting of the Society for Research on Nicotine and Tobacco this past Saturday, suggests that that reputation ought to be taken with a grain of salt — if not revised entirely.

A recently published study from UC San Francisco and George Washington University suggests that daily e-cigarette use may double the risk of heart attack. Conventional, combustible cigarette use was found to triple the risk.

“While a puff on an e-cigarette is likely less dangerous than a puff on a cigarette, most people who use e-cigs continue to smoke,” says study author Stanton Glantz, PhD.

“Dual use” — aka cutting back on conventional cigarette use while starting to use another tobacco product (like e-cigs or smokeless tobacco) — has become more prevalent. And it’s not without consequences: According to this study, smokers who use both e-cigarettes and regular cigarettes would see a five-fold increase in their risk of heart attack.

On the bright side, Dr. Glantz notes that the risk of heart attack appears to decrease immediately after quitting smoking. And former e-cigarette users’ risk drops immediately after quitting, too.

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