摘要：Objectives. Our study presents national estimates of the proportion of youths in each of 7 stages of smoking and investigates the associations between risk/protective factors and progression to established smoking. Methods. We analyzed data from the 1999 and 2000 National Youth Tobacco Surveys. Results. In 1999 and 2000, 48.6% of US adolescents had at least experimented with tobacco, and 7.8% were established smokers. Important correlates of progression to established smoking included parental advice not to smoke, antismoking lessons in school, susceptibility to tobacco industry advertising and promotion, peer smoking, and exposure to smoking at home. Conclusions. Interventions to stop adolescent progression to established smoking should target susceptible never smokers and early experimenters as well as those in later stages of smoking. Despite the decline in adolescent smoking from 1970 to 1984, 1 adolescent smoking prevalence in the United States increased during the 1990s. The Youth Risk Behavior Survey estimated the prevalence of past-30-day smoking among US high school students increased from 27.5% to 34.8% between 1991 and 2000. 2 Results from the Monitoring the Future Study show a rapid increase in prevalence between 1991 and 1997, which was followed by a dramatic decline in prevalence between 1997 and 2002. 3 Although the 2002 prevalence of 26.7% among high school seniors is the lowest high school senior prevalence ever measured in the Monitoring the Future Study, the fact that more than 25% of all high school seniors had smoked during the 30 days preceding the survey represents a huge potential source of addicted adult smokers. The model that we used for assessing progression toward established smoking is based on work by Leventhal and Cleary 4 and Flay. 5 Leventhal and Cleary describe the process of smoking onset as occurring in 4 distinct stages: (1) preparation, (2) initiation, (3) becoming a smoker, and (4) maintenance of smoking. Progression through these stages occurs over a period of 1 or more years. In the preparation stage, the nonsmoker begins to develop a self-image of being a smoker and forms ideas and beliefs about the utility of smoking. Initiation is defined as the first few tries. During the becoming a smoker stage, there is a gradual increase in the frequency of smoking, and persons smoke in an increasing variety of situations. During the maintenance of smoking stage, smoking is a part of self-regulation in a variety of situations, and smoking is used for a number of purposes that include pleasure, relaxation, and anxiety reduction. Flay 5 divides the maintenance stage into regular use (e.g., smoking every day before school or smoking every weekend), and addiction. Nicotine addiction is associated with compulsive smoking, cravings during periods of abstinence from use of tobacco, difficulty quitting smoking, and tolerance to increasing doses of nicotine. 6 In order to estimate from epidemiological data the numbers of youths in each stage of smoking, we adapted the above scheme as follows. First, we needed a stage for those nonsmokers who were not in the preparation stage. This stage is called not open to smoking. Nonsmokers in the preparation stage are characterized as open to smoking. Second, because the National Youth Tobacco Survey instrument did not measure the precise definition of initiation as described by Leventhal and Cleary 4 and Flay, 5 the initiation and becoming a smoker stages were slightly modified into 2 stages that we call early experimenters and late experimenters. Third, for consistency with other epidemiological studies, we needed a definition of current smoking. To accomplish this, the regular use and addiction stages described by Flay 5 were modified into 2 stages: nondaily current smoker and established smoker. Finally, we needed to account for youths who had progressed through the becoming a smoker stage but who were not smoking at the time of interview. We call them former smokers. Experimentation with smoking occurs primarily during adolescence. 7 Since the 1970s, the average age of first trying a cigarette and the average age of smoking daily has decreased. By the 1990s, few people began smoking regularly after 20 years of age. 7 Recognizing this, public health workers and educators have targeted prevention programs at increasingly younger persons. It is generally agreed that effective prevention requires a comprehensive set of conditions, including education, the promotion of social norms that promote not smoking, a reduction in smoking among peers and family members, and reductions in tobacco advertising and promotion targeted at young people. 7– 10 Our study presents national estimates of the prevalence of adolescents in each stage of progression to established smoking by age, race/ethnicity, and gender. Additionally, we explore selected risk and protective factors associated with progression to established smoking.
