Vaping or using e-cigarettes for a long period of time was associated with an increased risk of respiratory diseases -- including chronic obstructive pulmonary disease or COPD, chronic bronchitis and asthma -- in a new study.
The study, published in the American Journal of Preventive Medicine on Monday, is among the first bodies of research to examine the link between e-cigarette use and respiratory disease in the long-term, by analyzing e-cigarette use and respiratory disease during a three-year period.
"I was a little surprised that we could find evidence on incident lung disease in the longitudinal study, because three years is a while but most studies that look at the development of lung disease go over 10 to 20 years," said Stanton Glantz, senior author of the study and director of University of California, San Francisco's Center for Tobacco Control Research and Education.
"It's the first longitudinal study in the general population to link e-cigs with chronic lung disease," he said. "My guess is that if we were to come back and do this study in another five years, we would probably find bigger effects."
The study involved analyzing data from 32,320 adults in the United States on whether the adults have ever been told by a health professional that they had lung or respiratory conditions and whether they ever used e-cigarettes or smoked cigarettes or other combustible tobacco, among other demographic and clinical variables.
The data, which came from the Population Assessment of Tobacco and Health, were collected in 2013 to 2016.
The data showed that the risk of developing respiratory disease was significantly associated with former and current e-cigarette users -- and there was a stronger separate association with former and current smokers of cigarettes or other combustible tobacco, who either only smoked cigarettes or were users of both e-cigarettes and cigarettes.
"The risks of e-cigarettes and cigarettes are independent of each other, and so if you're a dual user -- meaning you're smoking and using e-cigarettes at the same time -- you have the risks of smoking multiplied by the risks of e-cigarette use," Glantz said.
"The odds of developing lung disease for the e-cigarette users was increased by about a factor of 1.3, and for the smokers it was about 1.6. If you're a dual user, it's 3.3," he said about the new study.
The study had some limitations, including that it was based on data the adults self-reported, which lends itself to recall bias.
The study adds to a proliferation of research aimed at measuring the impact of e-cigarette use on the lungs, heart, blood vessels and brain -- but experts have cautioned that much of that research remains in its early stages, often taking place in the lab or in animals.
The new study "applies to people as they use e-cigarettes in the real world," Glantz said.
Overall, "we're still learning so much about e-cigarettes," Dr. Maria Rahmandar, pediatrician and medical director of the Substance Use & Prevention Program at Ann & Robert H. Lurie Children's Hospital of Chicago, who was not involved in the new study, previously said in October.
When it comes to specifically vaping e-liquids, she said, "even these components that seem like they should be safe, we have no idea what they do once they're heated up, aerosolized and broken down into their byproducts, and what effect those have, especially when they're broken down into teeny tiny ultrafine particles that can go into deep parts of the lung."