Although the long-term health effects of electronic cigarettes are unknown, a new survey finds people who use the devices think of them as a safer alternative to tobacco and a means to break the smoking habit.

Researchers from the UK surveyed about 1,400 e-cigarette users on the Internet, 76 percent of whom said they started using their devices to replace cigarettes entirely. A much smaller percentage said their goal was to quit smoking or to improve their health.

One researcher who has studied e-cigarette users said the findings allay fears that people are using the devices to get more nicotine on top of what's already in tobacco cigarettes, instead of for smoking cessation.

"This study really indicates people are using them specifically to try to quit smoking or try to get off cigarettes. This dual-use idea is simply not a tenable idea anymore," said Boston University's Dr. Michael Siegel, who was not involved in the new research.

E-cigarettes were first introduced in China in 2004. The battery-powered devices let users inhale nicotine-infused vapors, which don't contain the harmful tar and carbon monoxide in tobacco smoke.

Lynne Dawkins and her colleagues from the University of East London write in the journal Addiction that there are currently over 100 brands of e-cigarettes, and 3.5 million devices were sold in 2012.

Despite the devices' growing popularity, the researchers say, little is known about who uses e-cigarettes and why.

For the new study, they created an Internet survey that was accessible from the websites of two e-cigarette manufacturers from September 2011 to May 2012. The survey took about 15 to 20 minutes to complete.

Overall, 1,123 ex-smokers and 218 current smokers from 33 different countries took the survey. About 16 percent of participants were from the U.S. and another 77 percent were from Europe. Seventy percent were men.

About three quarters of respondents said they started using e-cigarettes as a "complete alternative to smoking," and 22 percent said they started using the devices for "other reasons" - including stopping smoking (7 percent), for health reasons (6 percent) and to get around smoking restrictions (3 percent).

Some 86 percent said they had either not smoked cigarettes for several weeks or months since using the e-cigarette or that the amount they smoked had decreased dramatically.

The researchers also found that the majority of people responding to the surveys felt their health had improved since using the devices.

"Most people reported great health benefits. Their cough was reduced and their breathing was improved," said Dawkins, who added that the benefits are most likely from people smoking fewer cigarettes and not an effect of the devices or vapors.

Still, Dawkins told Reuters Health that more research is needed on the long-term effects of e-cigarettes.

Siegel said there's no question that e-cigarettes are safer than smoking, but there are concerns over some of the vapors' ingredients - including propylene glycol, which irritates airways, and formaldehyde, which is known to raise lung and nasal cancer risk when it's inhaled.

Despite the survey participants' feeling that their breathing eased with e-cigarettes, past research suggests the vapor has at least temporary negative effects on airways.

In 2012, a group of researchers said it found signs of airway constriction and inflammation within five minutes of people inhaling vapors from e-cigarettes. But that study only included a small group of people and the researchers couldn't say if those reactions actually lead to health problems.

The new study also had limitations.

For example, the participants who answered the survey were people who visited the manufacturers' websites and may not be representative of all e-cigarette users and their motivations.

Dawkins' group notes that some answers to the survey are also based on the participants' memory and that could lead to overestimating the devices' benefits.

"For the general public, they need to be better informed about what we know, what we don't know, what the advantages to using them are and what the disadvantages are," said Dawkins, who has received funding from e-cigarette companies to attend conferences in the past.