标题：Predictors of Sustained Smoking Cessation: A Prospective Analysis of Chronic Smokers From the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study
摘要：Objectives. Because US smoking rates have not declined during the past decade, there is a renewed need to identify factors associated with smoking cessation. Using a nested case–control design, we explored the association between ability to sustain cessation over an extended period and demographic, smoking, medical, and behavioral variables. Methods. We selected a sample of 1379 sustained quitters (abstinent from smoking for at least 40 months) and 1388 relapsers (abstinent for more than 8 months before relapse) from participants in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study, a nutritional intervention study involving Finnish men aged 50 to 69 years at baseline. Contingency table and multiple regression analyses were used to evaluate potential differences between the 2 groups on baseline variables. Results. Compared with sustained quitters, relapsers were more likely to report symptoms of emotional distress and higher levels of nicotine dependence, to drink more alcohol, and to report more medical conditions. Conclusions. Factors associated with both tobacco use and comorbid conditions impact an individual’s ability to maintain long-term smoking cessation. Understanding the underlying mechanisms of action and potential common pathways among these factors may help to improve smoking cessation therapies. Despite significant progress in smoking prevalence reduction within the United States since the mid-1990s, in the past 15 years, rates of smoking have remained virtually unchanged. 1 – 3 Smoking continues to be a significant public health issue with asubstantial associated cancer 4 and health care burden. 5 In the United States, current smoking rates are reported to be 21.6% of the adult population, with 440 000 deaths per year attributable to smoking. 3 These unchanged smoking rates have occurred within a context of widely marketed cessation medications and consistent reports of strong motivation by smokers to quit smoking, which speaks to the difficulty of successfully achieving cessation for many smokers. Approximately 40% of current smokers attempt to quit in any given year, but only 5% sustain abstinence for more than a few weeks, and most relapse within a week. 6 To effectively reduce the burden of tobacco use, there needs to be a better understanding of the factors associated with successful cessation. Smoking is a complex behavior that encompasses social, economic, environmental, behavioral, and physiological factors. 7 A comprehensive model of smoking should account for as many of these dimensions or factors as possible. Like other substance abuse and dependence behaviors, smoking occurs along a trajectory from experimentation and initiation to cessation attempts (and relapse). Therefore, to understand factors associated with smoking behavior along that trajectory, researchers must compare 2 groups who have similar histories—that is, groups in which both have reached a prerequisite “stage” before diverging on the behavior of interest. This allows any differences in the 2 groups to be more precisely attributed to the differences in the behavior of interest. To illustrate this point, consider that to compare participants’ responses to a stimulus first requires participant exposure to the stimulus. Likewise, to compare smokers’ progression from 1 stage of the smoking trajectory to the next, the smokers must be “exposed” to the previous stage on the continuum. For example, to assess liability to dependence, researchers are now effectively arguing that comparison groups must be exposed to nicotine, 8 or, in other words, individuals must progress through the cigarette-experimentation stage of the trajectory before liability to dependence can be assessed. In the case of smoking cessation, there are 2 relevant behaviors. The first is initiating a quit attempt and the second is sustaining that quit attempt. If the behavior of interest is sustained cessation, then a proper study design requires that all participants have made a quit attempt. In other words, smokers must progress to making a quit attempt before factors associated with quit length can be assessed. Individuals who have not made a quit attempt are not informative regarding their liability to relapse, and their inclusion in a study of sustained cessation presents a potential problem of misclassification bias. As an example, it has been suggested that a history of major depression may influence initiation of cessation but not maintenance of cessation. 9 – 10 To directly assess the impact of depression on the ability to sustain cessation (behavior of interest), individuals with and without a history of major depression who have all made a quit attempt (necessary exposure) should be compared. Previous literature has identified a number of factors that are likely to impact smoking cessation. Few studies, however, have clearly differentiated initiating versus sustaining cessation, 11 so the impact of those factors on quit attempts versus sustained cessation is unknown. Demographic variables that have been reported to positively influence cessation include male gender, older age, higher education, and indicators of higher socioeconomic status. 11 – 17 A number of smoking-related factors, including those associated with nicotine dependence, are related to increased difficulty with cessation. These include higher numbers of cigarettes per day, earlier age of smoking onset, few to no previous quit attempts, and indicators of nicotine dependence, such as shorter time to first cigarette in the morning. 18 – 21 Comorbid conditions have also been demonstrated to impact cessation, including behavioral symptoms and psychiatric disorders 22 – 24 and medical conditions. 25 – 29 Despite this seemingly comprehensive list, a limited body of research has considered the impact of these types of factors longitudinally or has addressed the contribution of more than 1 domain of factors within a single study. This is because, at least in part, of the lack of available longitudinal data that encompass a wide range of potential factors. To address this gap, we performed a nested case–control study on a sample drawn from a large, randomized longitudinal clinical trial of male smokers that contained a number of relevant variables including smoking use and history, demographics, comorbid medical conditions, and comorbid behavioral symptoms. In a selected sample of individuals who had made at least 1 quit attempt, we evaluated differences between those individuals who were able to sustain abstinence from smoking for at least 40 months (sustained quitters) to individuals who relapsed within 8 months (relapsers). These intervals were chosen a priori in an effort to maximize differences between our groups on the behavior of interest—sustained cessation.
