Introduction
The health problems caused by smoking have become an important consideration for public health. According to a World Health Organization (WHO) report, smoking is a significant factor leading to cardiovascular and respiratory diseases and more than 20 different types or subtypes of cancer[1, 2]. More than eight million people die from tobacco use each year, and most of these deaths occur in low- and middle-income countries[3]. However, tobacco use is not only harmful to smokers themselves, as second-hand smoke also affects non-smokers. According to WHO statistics, 1.2 million deaths each year are related to second-hand smoke exposure. More noteworthy is the impact of smoking, or second-hand smoke, on pregnant women and children. Each year, 65,000 children die from diseases related to second-hand smoke[4]. Smoking during pregnancy can also cause lifelong health problems for babies.[5] Therefore, various countries and organizations strive to find effective ways to help tobacco-dependent people quit smoking.
Alcohol use disorder (AUD) is one of the most common mental disorders in the world[6]. From 2012 to 2013, the prevalence rates of 12-month and lifetime AUD among adults aged 18 years and older in the United States were 13.9% and 29.1%, respectively, which accounted for approximately 33 million and 685 million people[7]. The corresponding Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) rates increased by 12.7% and 43.6% for 12-month and lifetime AUD, respectively, over the year 2001[8]. For many people, AUD is a chronic recurrent remissive disorder[9]. Regardless of the intervention, at least 60% of people with AUD will relapse within six months of treatment and return to dangerous levels of alcohol consumption[10, 11]. The chronic addiction cycle of AUD is related to a variety of biological, psychological, and social characteristics[12]. Among them, smoking is closely related to drinking. Studies have shown that smoking is associated with excessive drinking, increased alcohol withdrawal symptoms, a higher relapse probability, or early relapse after treatment in individuals recovering from dangerous drinking habits[13, 14]. Therefore, the development of smoking cessation treatment programs for this population is important for their long-term health and recovery from addiction.
For people with alcohol dependence or heavy alcohol use, smoking cessation drugs have also been shown to reduce alcohol consumption and cravings[15]. The drugs currently approved by the United States Food and Drug Administration for the treatment of alcohol dependence (such as acetamide, naltrexone, or disulfiram) have a small to moderate effect on drinking[16, 17] but may not be as beneficial for smoking cessation[18]. Nicotine replacement therapy (NRT), bupropion, and varenicline are widely available prescriptions for smoking cessation. In the United States and the European Union, these drugs are licensed as first-line treatments for adjuvant smoking cessation treatment and are widely recommended in many national guidelines[19]. There are also studies[20] testing the effectiveness and safety of these drugs for treating people with alcohol dependence who are trying to quit smoking.
The purpose of this systematic review and meta-analysis was to assess the effectiveness and safety risks of drug therapies for smoking cessation in patients with alcohol dependence. The outcomes will help to provide relevant information for alcohol addicts, clinicians, and policymakers.