The study, published March 2 in the American Journal of Preventive Medicine, examined data from a nationally representative survey of more than 600,000 U.S. adults who were asked about their smoking and vaping habits. Participants were also asked whether they had ever been told by a healthcare provider that they had prediabetes or “borderline diabetes,” slightly elevated blood sugar that isn’t yet full blown type 2 diabetes but makes people more likely to develop this condition. Roughly 9 percent of both current and former e-cigarette users had prediabetes, the study found. Compared with people who never vaped, the risk of prediabetes was 22 percent higher for current e-cigarette users and 12 percent greater for former vapers. And, among people who never smoked traditional cigarettes, current vaping was associated with 54 percent higher odds of developing prediabetes. “We were surprised by the findings associating prediabetes with e-cigarettes because they are touted as a safer alternative, which we now know is not the case,” says senior study author Shyam Biswal, PhD, a professor at the Bloomberg School of Public Health at Johns Hopkins University in Baltimore. More than 1 in 3 American adults have prediabetes, according to the Centers for Disease Control and Prevention (CDC). This occurs when the body can’t properly use the hormone insulin to convert foods into energy, leading sugar levels in the blood to rise over time. Prediabetes increases the risk for developing full-blown type 2 diabetes as well as the odds of heart attacks and strokes, the CDC notes. Several different blood tests can assess whether sugars are slightly above normal — indicating prediabetes — or high enough to be classified as type 2 diabetes. One common test estimates average blood sugar levels over two to three months by measuring a type of hemoglobin binds to glucose in the blood known as A1C. With this test, A1C levels between 5.7 percent and 6.4 percent indicate prediabetes, and readings of 6.5 percent and higher point to type 2 diabetes. One limitation of the study is that it relied on survey responses — not data from blood tests — to identify individuals who had prediabetes. Similarly, researchers lacked data on what types of cigarettes or e-cigarettes participants used, how often they indulged, and what amount of nicotine or other chemicals they were exposed to by vaping or smoking. “It not only the levels of nicotine in vape products, but perhaps the way individuals use the vape products that may put them at risk to develop diabetes,” says Patricia Fola, DNP, a certified tobacco treatment specialist and director of Northwell Health’s Center for Tobacco Control in Lake Success, New York. Smokers often have one or two cigarettes and then take a break, says Folan, who wasn’t involved in the study. Vapers, however, tend to use e-cigarettes throughout the day, even taking the devices with them to bed. With more continuous use, e-cigarettes can become more harmful, with a greater risk of prediabetes and other health problems, Folan adds. Vapers may also not know what harmful chemicals they’re exposed to when they use e-cigarettes, says Brian Oliver, PhD, a professor at the Woolcock Institute of Medical Research and University of Technology Sydney in Australia. “There is a lot of debate about which components of e-cigarettes cause detrimental effects in the body, and, simply put, everything is bad,” says Dr. Oliver, who wasn’t involved in the study. “Just like with cigarettes, there is no safe e-cigarette.”