Electronic cigarettes (e-cigarettes, ECs) are hand-held electronic atomization devices that generate mist by heating the e-liquid. The e-cigarettes are generally nicotine and flavor. The e-cigarette allows nicotine to be inhaled into the human body in the form of vapor, instead of the form of smoke. Inside the e-cigarette, the e-cigarette liquid is transferred to the atomization chamber through foamed nickel, and then turned on by the smoking air switch. The smart chip is driven by the current of the lithium battery to control the operation of the atomization chamber. The heating wire in the atomization chamber generates high temperature and atomizes the smoke liquid. Thereby forming a vapor mist that simulates the flue gas. Certain harmful substances in tobacco can cause smokers to suffer from smoking-related diseases, but because e-cigarettes do not burn tobacco, the user's exposure to harmful substances is lower than that of traditional smokers. Electronic cigarettes use high-tech smart chips and air switches to control the output and working status of the smoke, and gradually reduce the nicotine intake of smokers.

    We retrieved 50 studies involving 12430 subjects. These studies compared e-cigarettes with other smoking cessation methods, including:

• Nicotine replacement therapy (NTR), such as patches or nicotine gum;
• Varenicline (varenicline);
• Nicotine-free electronic cigarettes;
• Behavioral support, such as providing advice or consultation;
• No measures are taken.

    Existing research shows that compared with the use of nicotine replacement therapy (3 studies; 1498 people) or nicotine-free e-cigarettes (3 studies; 802 people), people who stop smoking for more than six months after using nicotine e-cigarettes The number of people may be more. Compared with no support or only behavioral support, e-cigarettes containing nicotine may be more helpful in quitting smoking (4 studies; 2,312 people).

    For every 100 smokers who use nicotine-containing e-cigarettes to quit, 10 may successfully quit smoking. In contrast, for every 100 smokers who use nicotine replacement therapy or nicotine-free e-cigarettes, 6 have successfully quit. For those who have no support or only behavioral support, only 4 people successfully quit smoking per 100 people.

    Evidence with moderate certainty indicates that compared with e-cigarettes without nicotine and nicotine replacement therapy, the use of e-cigarettes containing nicotine has a higher smoking cessation rate.