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Electronic cigarette use had neutral impact on cardiovascular events when used alone, but dual use with conventional tobacco cigarettes wasn't any less risky than only smoking, a study showed.

Exclusive use of e-cigarettes was on par with no use for overall risk of developing any cardiovascular disease (adjusted HR 1.00, 95% CI 0.69-1.45) and lower risk than only smoking (aHR 0.66, 95% CI 0.46-0.94), Andrew C. Stokes, PhD, of Boston University School of Public Health, and colleagues reported in .

For major events, exclusive e-cigarette use showed a nonsignificant trend for 35% higher risk than not smoking or vaping (aHR 1.35, 95% CI 0.75-2.42). And that combined risk of myocardial infarction, heart failure, or stroke with exclusive e-cigarette use wasn't significantly lower than with smoking alone.

Dual users were at significantly higher risk than nonusers for both sets of outcomes: a relative 54% greater incidence of any cardiovascular disease and 2.08-fold higher risk for the major events.

That risk from combined vaping and smoking did not differ from exclusive smokers for either outcome (aHR 1.01, 95% CI 0.81-1.26, and aHR 0.94, 95% CI 0.65-1.36, respectively).

"Our results suggest that combining smoking with e-cigarette use does not reduce [cardiovascular disease] events and that quitting both products is required to ensure a mitigation of risk," Stokes' group concluded.

Lower harm than combustible tobacco was a major rationale behind FDA of certain electronic nicotine delivery systems (ENDs) beginning last year.

"The manufacturer's data demonstrates its tobacco-flavored products could benefit addicted adult smokers who switch to these products -- either completely or with a significant reduction in cigarette consumption -- by reducing their exposure to harmful chemicals," said Mitch Zeller, JD, director of the FDA's Center for Tobacco Products, in the FDA announcement of the first such ENDs to clear the long-delayed regulatory process.

However, switching exclusively to e-cigarettes has proven uncommon, noted David Balis, MD, who runs the smoking cessation clinics at Parkland Hospital and at UT Southwestern Simmons Cancer Center, both in Dallas.

"We need to know both the risk and benefits of e-cigs. Do they help people quit smoking or not? I can't say that they do," he told 名媛直播. "Typically what they do is dual use ... They just smoke e-cigs at work and continue their cigarettes at home."

Indeed, Stokes and colleagues' study of data from the nationally representative PATH (Population Assessment of Tobacco and Health) cohort study turned up just 822 exclusive users of e-cigarettes compared with 6,515 who only smoked and 1,858 dual users out of the 24,027 eligible adult respondents.

In the five annual waves of self-reported data from 2013 to 2019, 50% of respondents were under age 35, and 51% were women. The study oversampled for tobacco users, young adults, and African-American individuals.

While it was reassuring that dual use wasn't worse than smoking alone for cardiovascular outcomes in the study, the perception that e-cigarettes are safer has driven greater use, Balis said.

"Most people think that they are safer than traditional cigarettes, but they still have risks," he added. "It's going to take us a while to figure that out. It's hard to sort out. We're never going to have a huge randomized, double-blind, placebo-controlled trial to show risk and efficacy."

The study didn't include individuals below age 18, but e-cigarette uptake by that group is a key area of concern raised by the FDA and anti-smoking advocates.

"We're concerned that we're going to have a whole generation of kids hooked on nicotine and this will be a gateway drug," Balis said. "That has to be somewhere in the equation."

Other limitations of the study included use of self-reported, non-adjudicated outcomes, a short follow-up period for prior 12-month incidence of cardiovascular events from waves two to five, and inclusion of former cigarette users in the nonuser control group. Also, there were low numbers of events in the exclusive e-cigarette use group (n=41).

Balis pointed to the number of participants lost to follow-up from the first to second wave who were excluded (n=5,873) as a concern as well.

"Larger studies with more cardiovascular outcome events and longer follow-up are warranted," Stokes' group noted.

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