(At the time, Juul, the top seller in the United States, was not available in England. Juul has much higher nicotine concentrations – either 59 milligrams or 35 milligrams.)
All participants had individual latitude within their study groups to closely approximate real-life scenarios. When the vapers finished their bottle of nicotine liquid, they could choose whichever flavor and nicotine strength to buy.
People who use nicotine replacement therapy can choose from a range of products, including the patch, gum, lozenge and nasal spray. They were even encouraged to combine them; most did so, usually opting for the patch and oral therapy.
Because self-reports of smoking abstinence are not considered reliable, researchers measured the amount of carbon monoxide in the participants' breath, and more precise validation.
Dr. Maciej Goniewicz, a co-author of the British study who is now a pharmacologist at the Roswell Park Comprehensive Cancer Center in Buffalo, N.Y., said that the success of e-cigarettes most likely reflects a combination of factors:
"It's about the method of delivery, the amount of nicotine and the user's behavior," he said. "E-cigarettes have the advantage that the user decides how and when to puff. Nicotine replacement therapy products have specific instructions, which are different for different products. "
Dr. Benowitz noted that the higher quit rates and compliance among e-cigarette users could be further explained because those subjects expressed more satisfaction with the devices than did the other group with their products.
In their editorial, Drs. Borrelli and O'Connor pointed to other studies on smoking cessation therapies: In one study, nicotine-replacement therapy and the antidepressant buproprion (Wellbutrin) achieved slightly higher abstinence rates than did e-cigarettes in this latest trial. The prescription drug varenicline (Chantix) has performed even moderately better. Furthermore, these products have been proven safe, they said.