Health risks associated with the use of electronic cigarettes: an interactive research map

We have systematically surveyed and created an interactive research map of existing literature on health risks associated with use of e-cigarettes. We included 1482 publications in the report. Since several of these may have reported to have more than one study design, such as both a publication with a human study and an animal experiment, the number of study designs included are in total 1760. Respiratory, cardiovascular as well as other adverse events (outcome not given under other code) were the health outcomes most often reported. Very few human studies were published the first years after the introduction of e-cigarettes in 2007, but from 2013 there was an increase. Case reports and case series led the way, followed by cross-sectional studies. We identified 41 randomised controlled trials (RCT). This study design is the most rigorous way of determining if a cause-effect relation exists between intervention (here use of e-cigarettes) and outcome. Only one of the RCTs had a follow-up time of six months or more. Among the other 105 studies with a control group, only six had a follow-up time of more than 2 years. Thus, any adverse impact of e-cigarette use on health which may take long time to develop, may remain undetected. Overall, the interactive research map gives a visual presentation of the broad variety of health consequences linked to the use of e-cigarettes and may be used to identify potential human health risks and possible research gaps. Identification of the latter can be useful for the discussion of focus of future research.The map shows what research is available, it does not assess the quality of the studies or size or severity of the health risk from using e-cigarettes