People who take up e-cigarettes for health reasons may be making things a lot worse for themselves. That's the major conclusion of a three-year study that looked at what happens to people after they start using e-cigarettes.

E-cigarettes are not harmless, but it has been suggested that for smokers of conventional cigarettes they may be a less harmful alternative. The current study helps answer questions about just how much they can help or harm.

Smokers could indeed reduce their risk of lung disease if they switched exclusively to e-cigarettes. The problem is that most e-cigarette users also smoke cigarettes.

Focusing on people who had no respiratory disease (asthma, bronchitis, emphysema or COPD) at the start of the study, researchers from the University of California, San Francisco (UCSF) then tracked how many non-smokers, smokers and vapers did develop these conditions over the next three years. The study is unrelated to E-cigarette or Vaping Product Use-Associated Lung Injury (EVALI), the serious and sometimes fatal lung disease discovered earlier this year among users of e-cigarettes.

People who used e-cigarettes were 1.3 times more likely to develop chronic lung disease than people who did not use them. People who smoked cigarettes were much more likely to develop these lung problems, increasing their risk by a factor of 2.6.

Unfortunately, the odds of lung problems were even higher for people who both smoked and used e-cigarettes. They experienced an increased risk factor of 3.3. Apparently, they get the combined risk of both types of smoke and are worse off than even smokers, perhaps because conventional cigarettes and the electronic kind insult the lungs in different ways. In any case, those who did both were the likeliest to develop lung disease.

This does suggest that cigarette smokers could indeed reduce their risk of lung disease if they switched exclusively to e-cigarettes. The problem is that most e-cigarette users also smoke cigarettes.

The conclusions are not happy ones. “This study contributes to the growing case that e-cigarettes have long-term adverse effects on health and are making the tobacco epidemic worse.

“What we found is that for e-cigarette users, the odds of developing lung disease increased by about a third, even after controlling for their tobacco use and their clinical and demographic information,” said the study's senior author, Simon Glantz, a professor of medicine at UCSF and director of the UCSF Center for Tobacco Control Research and Education, in a statement. “We concluded that e-cigarettes are harmful on their own, and the effects are independent of smoking conventional tobacco.”

For more details, see the article in the American Journal of Preventive Medicine.