Factors Perpetuating the Tobacco Problem
Over the past 40 years, much progress has been made in reducing the number of individuals who initiate tobacco use and in increasing the percentage of tobacco users who have quit. Current trends, however, indicate that reductions in the initiation of tobacco use have slowed and that the annual rate of cessation among smokers remains fairly low. This chapter provides an overview of the factors that impede additional progress and suggests that substantial and sustained efforts will be required to further reduce the prevalence of tobacco use and thereby reduce tobacco-related morbidity and mortality summarized in the introduction of this report and in numerous Surgeon General reports (see Box 2-1). First and foremost, tobacco products are highly addictive because they contain nicotine, one of the most addictive substances used by humans. Nicotine’s addictive power thus poses significant challenges to smoking cessation efforts at both the individual and the population levels. Second, factors such as distorted risk and harm perceptions, which are associated with the initiation and maintenance of tobacco use among young smokers, pose a continuing obstacle for prevention and control strategies. Finally, the apparent concentration of heavy smoking among populations with particular vulnerabilities and a possible emerging trend toward the later onset of less frequent smoking suggest that new approaches and strategies may be needed to reduce the prevalence of tobacco use on a permanent basis.
NATURE OF NICOTINE ADDICTION
Nicotine is considered a highly addictive substance (DHHS 1988; Royal College of Physicians 2000; WHO 2003). The science base supporting this
Surgeon General’s Reports on Tobacco Use 1964–2006
claim has been reviewed in-depth by the Institute of Medicine (IOM) in its 2001 report, Clearing the Smoke: Assessing the Science Base for Tobacco Harm Reduction (IOM 2001), and by the U.S. Department of Health and Human Services in the 1988 Surgeon General’s report, The Health Consequences of Smoking: Nicotine Addiction (DHHS 1988). These reports highlight the research literature showing that nicotine, through a complex set of mechanisms and actions that affect the neurochemistry of the brain, establishes and maintains dependence on tobacco use. The evidence derives from animal and human studies, from molecular biology and neurochemistry to behavioral studies. The evidence, in fact, is overwhelming. One of the main implications of addiction is the loss of control of drug (nicotine) use. This means that when a person would like to stop or reduce the level of consumption of an addictive drug, like nicotine, it is difficult to do so.
Physical dependence on nicotine is associated with psychoactive as well as positive and negative reinforcing effects, the development of tolerance, and the experience of withdrawal symptoms. Dependence is associated with direct and indirect effects of nicotine on brain neurotransmitters, which are directly related to the behaviors associated with addiction and withdrawal. In addition, behavioral factors, including conditioning, play an important role along with the neurochemical effects. Finally, there are some physiological effects of cigarette smoke independent of the nicotine that might contribute to the overall pleasure and addictive properties of nicotine.
Nicotine from cigarette smoke is rapidly absorbed in the lungs, from which it is quickly passed into the brain. Nicotine exerts its actions by binding to nicotinic cholinergic receptors (nAChRs) in the brain (Dani and De Biasi 2001). Composed of five subunits, the main receptor mediating nicotine dependence is believed to be the α4β2 nicotinic cholinergic receptor. Mice lacking the β2 subunit gene do not self-administer nicotine, nor do they exhibit other behavioral effects associated with nicotine exposure. The α4 subunit is associated with nicotine sensitivity. Mutations of that subunit lead to increased sensitivity to nicotine-induced reward behaviors as well as to effects on tolerance and sensitization (Tapper et al. 2004).
Nicotine affects many neurotransmitter systems: dopamine, norepinephrine, acetylcholine, serotonin, γ-aminobutyric acid, glutamate, and endorphins. The major effect of nicotine is to stimulate release of these transmitters. The result of dopamine release is critical to the reinforcing effects of nicotine and occur in the mesolimbic area, the corpus striatum, and the frontal cortex. A pathway of particular importance to drug-induced reward involves the dopaminergic neurons in the ventral tegmental area of the midbrain and the release of dopamine in the shell of the nucleus accumbens. Dopamine release signals a pleasurable experience. For example, the threshold for intracranial self-stimulation in rats, a model for brain reward, is lowered acutely with nicotine exposure, indicating greater reward.
As would be expected with substances associated with tolerance and addictive properties, neuroadaptation occurs with chronic nicotine exposure. A suspected biological correlate of this is an increase in nAChRs in the brain. This increase is thought to reflect nicotine-mediated desenstitization, meaning that more nicotine is required to deliver the same neurochemical effect. For example, nicotine withdrawal in rodent models is associated with increased threshold for intracranial self-stimulation, indicating reduced reward due to inadequate dopamine release. Independent of nicotine effects, cigarette smoking is associated with decreased activity of monoamine oxidase enzymes in the brain, which are associated with the degradation of dopamine. Inhibition of monoamine oxidase activity would augment nicotine effects of increasing dopamine levels and contribute to positive reinforcement, tolerance, and addiction.
As most smokers report, stopping smoking is acutely associated with withdrawal symptoms of irritability, restlessness, anxiety, problems getting along with friends and family, difficulties concentrating, increased hunger and eating, and cravings for tobacco. Another symptom is the lack of pleasure or enjoyment, known as anhedonia. These symptoms are believed to be due to the relative deficiency in dopamine release, related to nicotine-mediated changes in receptor function and structure. Nicotine addiction is thus sustained by a combination of positive effects of nicotine on neurotransmitter levels related to pleasure and arousal, the dampening effect of those pleasure or reward mechanisms over time, and the need for continued nicotine exposure to avoid the negative affects related to the decreased neurotransmitter levels, particularly that of dopamine, that would occur without nicotine. However, in addition to the pharmacological mechanisms of nicotine, conditioning is also thought to play an important role in tobacco addiction.
With regular drug use, specific moods or other environmental factors, known as “cues,” become associated with the pleasurable or rewarding effects of the drug. This association between the cues and the anticipated pleasure associated with the drug, known as conditioning, is a powerful contributor to addiction (O’Brien 2001). Smoking is maintained in part by conditioning. For example, smoking becomes associated with specific behaviors, such as drinking a cup of coffee or alcohol. Repetition of these coexisting behaviors over time leads to the behavior becoming a cue the person to want to smoke. Behaviors can be conditioned to either the positive or negative reinforcing effects of nicotine. For example, because smoking becomes associated with relieving the negative affects of nicotine withdrawal, the smoker can associate smoking with relieving other negative feelings, such as stress. Managing conditioned behaviors is often an important factor in the success of nicotine cessation.
Smoking also facilitates nicotine dependence through sensorimotor factors associated with the act of smoking. Several studies have found that sensorimotor factors play an important role in maintaining smoking behavior in some smokers (Brauer et al. 2001; Naqvi and Bechara 2005; Rose 2006; Rose et al. 2000, 2003). A number of researchers, including Rose and colleagues, have used nicotinized and denicotinized cigarettes to study the separate roles of pharmacological actions of nicotine and the sensory/behavioral aspects of cigarette smoking on smoking withdrawal and smoking behavior (Rose et al. 2000). The results of those studies indicate that smoking denicotinized cigarettes can produce satisfaction as well as psychological rewards and can reduce the craving sensations. This finding is consistent with reports from smokers who described positive feelings as they inhale cigarette smoke but who do not experience these feelings when these sensory effects are blocked (Rose 1988; Rose et al. 1999). It has been suggested that the stimulation of nicotinic receptors on vagal nerve endings in the respiratory tract plays a role in mediating the immediate subjective effects of cigarette smoking (Rose et al. 1999).
The findings from this body of work thus suggest that airway sensory replacement may be an important aspect to be considered when determining the smoking cessation strategies to be used for some smokers (Rose et al. 1999; Westman et al. 1995).
In recent years, a body of research literature on the genetics of tobacco use has emerged. Over the past decade, researchers have cast some light on the role of genetic factors in tobacco use and dependence (Hall et al. 2002; Kendler et al. 1999; Lerman and Berrettini 2003; Li 2003, 2006; Madden et al. 1999; Sullivan and Kendler 1999). A review of a number of studies with twins suggests a significant genetic component in the initiation and maintenance of tobacco use (Kendler et al. 1999; Sullivan and Kendler 1999). On the basis of findings from studies of families, adopted children, and twins, Sullivan and Kendler estimate that a genetic influence may contribute approximately 60 percent to the possibility of smoking initiation, with environmental and personal influences contributing the remainder (Sullivan and Kendler 1999). Genetic influences are also estimated to contribute significantly (about 70 percent) to nicotine dependence.
Tyndale (2003), meanwhile, has reported on differences in the estimates of genetic influences on smoking initiation by gender, with rates ranging from 32 to 70 percent among females and 31 to 61 percent among males (Tyndale 2003). Estimates of the genetic influence on smoking persistence range from 4 to 49 percent among females and from 50 to 71 percent among males. Additional studies indicate that the age of smoking onset, the amount smoked, and smoking persistence are also influenced by genetics (Heath et al. 1999; Koopmans et al. 1999; Madden et al. 1999).
The number of studies that have assessed the role of specific genes in smoking behavior continues to grow. The work of Malaiyandi and colleagues (2005), for example, suggests that cytochrome P450 (CYP) 2A6, the liver enzyme which mediates the conversion of nicotine to cotinine, may play an important role in smoking (Malaiyandi et al. 2005). In a review of recent genetic studies of nicotine dependence, Li (2006) presents evidence that several genes may be implicated in nicotine dependence (Li 2006). Some of these genes include gamma-aminobutyric acid 2, which modulates neuronal excitability; nicotinic acetylcholine receptor alpha4, (CHRNA4), which modulates tolerance to nicotine; decarboxylase and brain-derived neurotropic factor, which influence dopamine and serotonin, which play important roles in the reward system of addiction; and the catechol-O-methyltransferase gene, which plays a role in the dopaminergic circuits central to the reward system. These and future studies of the role of genetic influences on smoking have the potential to further the understanding of nicotine addiction and its treatment.
The role of genetics in identifying the best treatment strategies for subgroups of smokers is another important emerging area of research. Pharmacogenetics researchers have examined a variety of polymorphisms and gene variances in smokers and their response to a number of current and widely used cessation pharmacotherapies for nicotine dependence. The results of these studies suggest that specific subgroups of smokers have a significantly higher probability of abstinence when they use nicotine patches, nicotine nasal spray, and bupropion treatment (Lerman et al. 2002, 2004; Swan et al. 2005). However, these studies generally involve small numbers of subjects and the genetic associations need to be replicated. It is expected that continuing research in this area will provide results that can better guide clinicians in selecting the best treatment options for individuals who want to quit smoking and will aid the in development of new drug targets that will help in cessation (Lee and Tyndale 2006).
Once the grip of nicotine addiction has taken hold, quitting is hard. Epidemiological data from the 2004 National Health Interview Survey (NHIS) suggest that of the 44.5 million U.S. adults who were current smokers, about 40.5 percent (or 14.6 million) of smokers reported that they had stopped smoking for at least 1 day in the preceding 12 months in an effort to quit (CDC 2005b). Although the number of smokers who attempt to quit is significant, actual quit rates are about 5 percent, and in studies that include biochemical verification of abstention, the actual quit rate is about 3 percent (Shiffman 2004). Some researchers suggest that each year only about 2 percent of smokers will quit permanently (Hughes 2003;
Shiffman 2004). Eventually, however, 50 percent of individuals who have ever smoked will quit (CDC 2005a).
Many smokers regret having engaged in smoking behavior. One major study of smokers in four countries (the United States, Canada, the United Kingdom, and Australia) found an overwhelming high level of regret among adult smokers (about 90 percent). This finding was consistent across the four countries (Fong et al. 2004). Regret was defined as responses of strong agreement and agreement with the statement “If you had to do it over again, you would not have started smoking.” Although the overall level of regret was high, it was more likely to be experienced by older smokers, women, and those who had tried to quit more often.
With such high levels of regret, it is not surprising that 70 percent of smokers report an interest in quitting (Fiore et al. 2000; Hughes 1999; Hymowitz et al. 1997). Interest in quitting, however, does not translate into immediate plans or actions to quit (Larabie 2005). When smokers interested in quitting are queried about their specific plans to quit, only 10 to 20 percent report a plan to quit in the next month (Etter et al. 1997). Eventually, however, about 70 percent of smokers will make at least one quit attempt (Fiore et al. 2000).
Individuals who contemplate taking steps to quit often engage in a process of weighing the pros and cons of smoking (Velicer et al. 1999). In a comprehensive review of the literature spanning five decades, McCaul and colleagues found that the primary factor motivating smokers to quit is a health concern (McCaul et al. 2006). This finding was robust across retrospective studies of former smokers, cross-sectional studies of current smokers, and prospective studies of smokers in cessation studies. Health concerns were also reported as a primary motivating factor among smokers in the Community Intervention Trial for Smoking Cessation (COMMIT) cohort study of smokers monitored for 13 years. Smokers who had made one serious attempt to quit in the period from 1993 to 2001 reported the most common reasons for quitting were concerns for current and future health (92 percent), expense (59 percent), concern for effects on others (56 percent), and setting a good example for children (52 percent) (Hyland et al. 2004). These results are similar to those found in an early COMMIT survey (1988 to 1993) (Hymowitz et al. 1997).
Physicians are in a unique position to encourage smoking cessation by their patients (Fiore et al. 2000; Russell et al. 1979; Schroeder 2005). Physician counseling and intervention are estimated to double the likelihood of quitting (Goldstein et al. 1997). Many physicians, however, miss clinical opportunities to counsel patients. Schroeder (2005) notes that only a minority of physicians are aware of and implement the 5 A’s (ask, advise, assess, assist, and arrange) of cessation treatment.
A number of factors may contribute to physicians’ limited participation
in encouraging patients to stop smoking. External factors such as time constraints, lack of financial incentives, or reimbursement for cessation services can be a hindrance (Schroeder 2005), as can the lack of smoking cessation educational resources in the practice setting or in the community (Tremblay M et al. 2001). Physicians’ lack of knowledge, expertise, or skill in smoking cessation, as well as their negative beliefs and perceptions regarding their role in getting patients to quit have also been noted (Schroeder 2005; Tremblay et al. 2001). Physicians, for example, may believe that patients can’t quit or do not fully understand that patients may try and fail a number of times before they are successful at quitting. Physicians may also fear a negative response from a patient if quitting smoking is addressed in the clinical visit (Schroeder 2005). Strategies to support physicians in engaging patients to quit smoking need to be identified and tested. Schroeder (2005), for example suggests a shortcut option encouraging physicians to ask, advise, and refer. Such strategies, however, will require enhanced support for community resources available for referral, such as quitlines.
Stages of Change
The desire or intention to quit smoking, along with an eventual attempt to quit smoking, has been viewed by many researchers as a series of transitional change stages by proponents of the transtheoretical model of change. The stages of change include precontemplation, contemplation, preparation, action, and maintenance (Prochaska and DiClemente 1983). Early studies that used the model found that cessation activity differed substantially by stage of change and that stages of change were, in turn, predictive of quit attempts and the success of quitting at 1 and 6 months (DiClemente et al. 1991).
Wewers and colleagues (using data from Current Populations Surveys conducted in 1992–1993, 1995–1996, and 1998–1999) used the Stages-of-Change Model to study movement in the readiness to quit among Americans in the 1990s (Wewers et al. 2003). The percentage of individuals in each stage of change over the three survey periods ranged from 63.7 to 59.1 in the precontemplation stage (not seriously thinking of stopping within the next 6 months), 33.2 to 28.7 percent in the contemplation stage (planning on quitting in the next 6 months but not in the next 30 days or planning on quitting in the next 30 days but making no quitting attempts in the past 12 months), and 9.3 to 7.7 percent in the preparation stage (planning on quitting in the next 30 days and making a quit attempt of at least 24 hours duration in the past 12 months). Overall, the study results indicated very little movement in the stages of readiness to change among the U.S. population in the 1990s.
Some surveys examining the stages of change and quitting have de-
scribed mixed results. Etter (2004) reported an association between smoking prevalence and stages of change: a higher prevalence of smoking was associated with a lower motivation to quit, as were fewer quit attempts and higher levels of cigarette consumption (Etter 2004). These findings were reported on the basis of data from all 50 U.S. states; these results were seen in the 1996 and 1999 Behavioral Risk Factor Surveillance System surveys but not in the 1993 survey.
Although the Stages-of-Change Model has been useful in moving cessation research from a focus on smoking and not smoking end points to the process of change from smoking to nonsmoking, questions have been raised about the need to elucidate more clearly other variables that may be implicit in the stages of change (intention to change, past quit attempts, current behavior, and the duration of the current behavior) but that are not explicitly assessed in research studies of stages of change and quitting (Etter and Sutton 2002). Recently, West (2005) has questioned the stages of change paradigm as a description of the cessation process. He found that the majority of smokers stop smoking impulsively, without going through stages of precontemplation and contemplation. Of course, this does not mean that concerns about health and the other harmful effects of smoking have not played an important role in the attempt to quit.
Understanding which smokers will eventually take steps to quit, who will be successful at quitting, and how long smoking abstinence will endure can be difficult to discern from the literature. Difficulties arise because periods of cessation vary, as do definitions of “abstinence.” Definitions of smoking cessation in the literature typically range from a 24-hour point-prevalence abstinence rate to a 6-month prolonged period of abstinence (Velicer and Prochaska 2004). Some researchers account for whether the smoker has had smoking lapses or was totally abstinent during the period of cessation reviewed (Hughes et al. 2004). Cessation outcomes can also vary depending on whether quitting was unaided or assisted with behavioral or pharmacological therapies. What is clear is that smoking careers can be long in duration. Birth cohort data from NHIS indicate that half of 15- to 17-year-olds who reported smoking at least 100 cigarettes in their lifetime will likely continue to smoke for 16 to 20 years (Pierce and Gilpin 1996). The literature also reinforces the view that nicotine addiction and tobacco dependence show some similarities with chronic diseases that are characterized by periods of relapse and remission (Fiore et al. 2000); thus the path to smoking cessation will include cycles of abstinence, lapses, relapse, and abstinence.
Smokers who move from contemplating quitting to action typically
fail. A study of self-quitters (Garvey et al. 1992) found that the majority of relapses occurred in the first few days and weeks post-cessation. Although most self-quitters (87.2 percent) relapsed within 1 year of their quit date, the majority of relapses occurred in the first few days and weeks after stopping: 13 percent relapsed by 1 day after quitting, 32 percent by 3 days, 49 percent by 1 week, and 62 percent by 2 weeks.
The results of another study of motivated self-quitters support the findings of an early relapse to smoking (Hughes et al. 1992). That study reported smoking cessation results by the use of two measures: one measure that reflected complete abstinence and another measure that reflected some smoking (smoking an average of one cigarette per day or less since the last follow-up and observer verification of no smoking of more than 10 cigarettes on any 2 days). The study findings, which used biochemical verification, indicated that 33 percent of self-quitters were abstinent at 2 days, 24 percent at 7 days, 22 percent at 14 days, 19 percent at 1 month, 11 percent at 3 months, 8 percent at 6 months, and 3 percent at 6 months. By using the more relaxed criteria, 47 percent were abstinent at 2 days, 38 percent at 7 days, 32 percent at 14 days, 27 percent at 1 month, 20 percent at 3 months, and 11 percent at 6 months.
Under a worst case scenario of unsuccessful quitting attempts, Piasecki and colleagues described cessation attempt “fatigue,” or a decrease in motivation and ability to stay abstinent (Piasecki et al. 2002). Cessation attempt fatigue is noted to be associated with lower expectations for cessation success, a reduced ability to cope or to believe in having the capacity to quit or stay abstinent, and fewer resources to exert control over behaviors or actions related to tobacco use. Smoking lapses and relapses to smoking, however, do not necessarily represent total quit failures but, rather, represent learning experiences along the pathway to cessation.
Early on in a cessation attempt, smokers may face a number of circumstances that encourage a smoking lapse, including symptoms associated with nicotine addiction (withdrawal, negative affect, urges, and cravings), the presence of social environmental factors such as smokers in the environment, or easy access to tobacco products (Brauer et al. 1996; Piasecki 2006). Although any smoking behavior after quitting has been identified as a very strong predictor of an eventual relapse (Kenford et al. 1994; Shiffman et al. 2006; Westman et al. 1997), it may not necessarily be a final outcome. Hyland and colleagues (2006) found that quit attempts in the previous year and a longer duration of past quit attempts were important predictors of new quit attempts, suggesting that some smokers will continue to attempt to abstain from smoking, despite past lapses or relapses (Hyland et al. 2006).
Other researchers note that smokers with failed quit attempts may reduce the intensity of smoking and the level of addiction for several months
after a relapse (Knoke et al. 2006). The ability to reduce smoking levels may prime relapsed smokers to be more successful in latter quit attempts. Results from the Community Intervention Trial for Smoking Cessation (surveys from 1988, 1993, and 2001) found a significant increase in quitting among participants who were able to reduce their daily cigarette consumption by 50 percent. Those who reduced their cigarette consumption by more than 50 percent were 1.7 times more likely to quit smoking by 2001 than those who did not reduce their cigarette consumption (Hyland et al. 2005).
Smokers who attempt to quit smoking with the use of some assistance tend to fare better than self-quitters; however, many smokers may not be informed about effective cessation methods (Hammond et al. 2004). Although it is not the intention of the committee to provide an exhaustive review of cessation therapies, it is important to highlight current guidelines for assisting smokers with quitting. The U.S. Department of Health and Human Services’ Clinical Practice Guideline for Treating Tobacco Use and Dependence identifies three counseling and behavioral therapies that are effective in helping smokers quit. These include providing smokers with practical counseling that focuses on (1) problem-solving skills and skills training for relapse prevention and stress management, (2) providing social support as part of treatment, and (3) helping smokers obtain social support outside of treatment.
Current guidelines also recommend eight effective pharmacotherapies that can assist smokers in their attempts to quit. Five therapies are nicotine-based (nicotine gums, patches, nasal sprays, inhalers, lozenges/tablets), two are antidepression medications (bupropion and nortriptyline), and one is a medication (clonidine) that is used for the treatment of hypertension (Fiore et al. 2000; Foulds 2006; Henningfield et al. 2005). Recently, varenicline, a nicotinic cholinergic receptor partial agonist, has been marketed for smoking cessation. Bupropion, nicotine inhalers, nasal sprays, and nicotine patches are considered first-line medication treatments that double long-term abstinence rates compared with those achieved with placebo. Nicotine gum, also a first-line treatment, improves the long-term abstinence rate by about 30 to 80 percent. There is emerging evidence from a few studies that selected use of combinations of nicotine replacement therapies (a nicotine patch with either a nicotine gum or a nicotine nasal spray) may have greater efficacy than a single form of nicotine replacement, but this has not been proven (Fiore et al. 2000).
The previous sections can be summarized succinctly: nicotine in cigarettes and other forms of tobacco is highly addictive. Once addiction takes
hold, it is difficult to stop using nicotine-containing products, although a number of therapies can improve the chances of quitting. Tobacco use is also harmful to one’s health and to the health of others. Since 1964 (see Box 2-1 for a list of Surgeon General reports published from 1964 to 2006) the evidence has been building that, “smoking harms nearly every organ of the body, causing many diseases and reducing the health of smokers in general” (CDC 2004). More recently, the Surgeon General reported that, “secondhand smoke causes premature death and disease in children and in adults who do not smoke” (DHHS 2006). As a result, 90 percent of smokers regret having started to smoke, 70 percent want to quit and have made at least one quit attempt, and, at any given time, 40 percent are actively trying to quit or are thinking of quitting within the next six months.
Given the clear and consistent evidence that smoking is addictive, quitting is difficult, and smoking is harmful to the health of everyone exposed to tobacco smoke, why do new smokers emerge each year? Because about 90 percent of adult smokers initiated smoking before the age of 18 years (DHHS 1994), addressing this question requires an understanding of why youths begin to smoke. Explanations of adolescent risk taking, including tobacco use, often point to adolescents’ underestimation of the chance that a negative outcome will occur to them (Elkind 1967; Reyna and Farley 2006; Slovic 2001), a sense of personal invulnerability to harm (Elkind 1967, 1978), a failure to appreciate the personal applicability of known risks (Arnett 2000; Romer and Jamieson 2001b), and a general immaturity that impairs judgment (Steinberg and Cauffman 1996). Theories of health behavior have incorporated this notion, theorizing that perceptions of low risk are related to engagement in health-compromising behaviors (see, for example, the Health Belief Model (Rosenstock 1974), the Theory of Planned Behavior (Ajzen 1985), Self-Regulation Theory (Kanfer 1970), and theories of decision making [e.g., (Janis and Mann 1977)]; see also Transtheoretical Model of Change (Pallonen et al. 1998; Prochaska 1994; Prochaska and DiClemente 1983; Prochaska et al. 1992). This section provides a review of the literature on adolescents’ and young adults’ tobacco-related perceptions.
Perceptions of Risks of Using Tobacco
The literature on perceptions about tobacco use among adolescents and young adults is reviewed elsewhere in this report. A number of studies have assessed the extent to which adolescents and young adults recognize and appreciate the risks of smoking. Although some studies show that smokers
either overestimate (Borland 1997; Kristiansen et al. 1983; Viscusi 1990; 1991; Viscusi et al. 2000) or underestimate (Schoenbrun 1997; Sutton 1997) the particular risks of smoking compared with the actual risk from epidemiological data, most studies agree that adolescents and young adults are aware of many of the risks involved with tobacco use. In particular, they are aware that smoking involves a significant risk of lung cancer and other health outcomes (Jamieson and Romer 2001a). However, the literature also indicates that adolescents are not aware of the full extent to which smoking is harmful (Arnett 2000; Covington and Omelich 1992; Eiser and Harding 1983; Halpern-Felsher et al. 2004; Hansen and Malotte 1986; Leventhal et al. 1987; Virgili et al. 1991), nor do they fully understand the extent to which tobacco use can shorten the life span (Romer and Jamieson 2001a). More importantly, adolescents are less likely to believe that the risk of addiction and the related health consequences apply to them. To complicate matters, adolescents show an incomplete understanding of the addictive nature of tobacco use that is related, in part, to their inaccurate assessment of smoking risks and their belief that they can quit at any time and therefore avoid addiction (Arnett 2000; Slovic 1998). Furthermore, they believe that smoking risks can be counteracted by altering the amount that they smoke, when they smoke, or what they smoke (e.g., “light” versus regular cigarettes) (Kropp and Halpern-Felsher 2004).
Whether such perceptions, or misperceptions, actually motivate or predict tobacco use is a complicated question. For example, although the concept of adolescent invulnerability is widely used to explain why adolescents smoke, the few studies that have examined the relationship between personal risk perceptions and tobacco use have yielded mixed results. Although some studies find that adolescents who have smoked perceive greater personal risks (Gerrard et al. 1996; Johnson et al. 2002; Resnicow et al. 1999), others show that smokers perceive less personal risk (Arnett 2000; Covington and Omelich 1992; Eiser and Harding 1983; Goldberg et al. 2002; Urberg and Robbins 1981; 1984; Virgili et al. 1991). The following sections details smokers’ (particularly adolescent smokers’) risk-related beliefs regarding several such aspects of tobacco use.
Beliefs Regarding the Effects of Smoking
Adolescent smokers tend to overestimate some smoking risks and underestimate others. In general, they understand that smoking causes lung cancer, but they also overestimate the degree to which it does. Jamieson and Romer reported that among 14- to 22-year olds surveyed in the Annenberg Tobacco Survey, 70 percent of smokers and 79 percent of nonsmokers overestimated the risk of lung cancer attributed to smoking (Jamieson and Romer 2001b). The survey respondents also underestimated the degree
to which smoking can shorten a smoker’s life. Although the majority of smokers (68 percent) and nonsmokers (79 percent) recognize that smoking shortens one’s life, close to 26 percent of smokers and 18 percent of nonsmokers responded that they did not know whether this was actually the case. When asked more specifically about the number of years that smoking can shorten a life span, 44 percent of smokers and 48 percent of nonsmokers correctly identified that smoking can shorten one’s life by 5 to 10 years; however, 28 percent of smokers and 19 percent of nonsmokers reported that they did not know. A high proportion of respondents also reported inaccurate assessments of the lethality of smoking compared with those of other behaviors. Many of those surveyed failed to recognize that smoking causes more deaths than gunshots and car accidents (42 percent) or alcohol and the use of other drugs (62 percent).
Another important finding from the Annenberg Tobacco Study concerns “optimism bias,” that is, smokers’ belief that the smoking risk is lower for themselves than for others engaging in similar behaviors (Weinstein 1989). In other words, an abstract understanding of the nature and the magnitude of smoking risks does not necessarily translate into a personalized appreciation of the hazards to oneself. In their analysis of the survey data, Romer and Jamieson found that, among smokers who correctly estimated that half of lifetime smokers die from smoking-related causes, 40 percent viewed their own smoking as less than “very risky” (the scale ranged from “very risky” to “not at all risky”). Among respondents who estimated that 60 percent or more of lifetime smokers die from smoking-related causes, 25 percent did not view their own smoking as very risky (Romer and Jamieson 2001a). Arnett reported similar results from a survey of both adolescents and adults (Arnett 2000). Arnett found that in both of these groups, smokers were more than twice as likely as nonsmokers to doubt that they would die from smoking, even if they were to smoke for 30 to 40 years. Moreover, a nontrivial proportion of adolescent smokers (29 percent) doubted slightly or strongly that they would die from smoking if they smoked for 30 to 40 years. Other studies have also shown that participants who reported that they smoked rated the chance that a negative health outcome as well as a negative social outcome (e.g., getting into trouble) would occur lower than did participants who did not smoke (Arnett 2000; Halpern-Felsher et al. 2004; Virgili et al. 1991). Furthermore, risk perceptions vary by level of smoking (Chassin et al. 2000; Halpern-Felsher et al. 2004; Soldz and Cui 2002) or stage of smoking (Pallonen et al. 1998; Prokhorov et al. 2002), with individuals who have smoked longer and more often perceiving fewer risks than those who have smoked for shorter periods and less often. Similarly, studies have found that perceived health and social risks are related to behavioral intentions and that these intentions are the most important and immediate determinants of behavior (Ajzen 1985; Distefan
et al. 1998; Fishbein and Ajzen 1975; Pallonen et al. 1998; Parsons et al. 1997; Prokhorov et al. 2002).
Beliefs Regarding Addiction and Cessation
Researchers have also examined the extent to which adolescents understand the grip of addiction and the implications of addiction on quitting. The results of these studies indicate that, although adolescents might be aware of the health and long-term risks of smoking in general, they are much less aware of the addictive nature of smoking. There are also indications that adolescent smokers might be less worried about the long-term risks of smoking, in part because they believe that they can quit smoking easily and at any time.
Weinstein and colleagues examined youth and adult smokers’ beliefs about the difficulty of quitting smoking and the nature of addiction (Weinstein et al. 2004). On the basis of data from two nationwide surveys, they found that most (96 percent) smokers, both youth and adults, agreed that the longer you smoke, the harder it is to quit. A high proportion of both groups also agreed that signs of addiction appear very quickly if a teenager starts smoking half a pack of cigarettes a day: 80 percent of youth and 79 percent of adults said signs of addiction appeared in a few months or less. The youths examined in that study also tended to claim that they were less addicted than the average smoker.
Similarly, Jamieson and Romer found that a substantial proportion of smokers understood that the properties of tobacco are addictive, but they did not fully appreciate the implications for quitting (Jamieson and Romer 2001b). Their survey results showed that, whereas 82 percent of smokers agreed that cigarettes have addictive chemical properties, nearly 60 percent of those smokers believed that quitting is either very easy or possible for most people if they really try. These findings are consistent with those reported by Arnett who showed that nearly 60 percent of adolescents believed that they could smoke for a few years and then quit (Arnett 2000). However, most of them do not quit. Smoking continues beyond the high school years, with 63 percent of 12th grade daily smokers still smoking daily 7 to 9 years later, even though only 3 percent of them estimated in high school that they would still be smoking in 5 years (Johnston et al. 2004).
Beliefs Regarding So-Called “Light” Cigarettes
Another area where smokers, including adolescents, have a distorted understanding of the risks of smoking is in the comparative effects of so-called “light” cigarettes and regular cigarettes. Adolescents often smoke
“light” cigarettes to counteract the risks of smoking. In a study conducted by Kropp and Halpern-Felsher, the participants were found to believe—incorrectly—that they would be significantly less likely to get lung cancer (and other adverse health outcomes) if they smoked “light” cigarettes rather than regular cigarettes (Kropp and Halpern-Felsher 2004). Adolescents also mistakenly thought that it would take significantly longer to become addicted to “light” cigarettes and that their chances of quitting smoking were higher with “light” cigarettes than with regular cigarettes, even though it is now well established that most smokers achieve the same level of exposure to nicotine and tobacco-related toxins when they smoke so-called “light” cigarettes (IOM 2001). They also “agreed” or “strongly agreed” that regular cigarettes deliver more tar than “light” cigarettes and that “light” cigarettes deliver less nicotine than regular cigarettes. Although some of the adolescents in that study were aware of the health risks and addictive properties associated with “light” cigarettes, the data showed that some 22 percent of the adolescents were uncertain about the differences between regular and “light” cigarettes and that between 25 percent and 35 percent of the adolescents mistakenly thought that health risks were more likely to be associated with regular cigarettes than with “light” cigarettes.
Adolescent Weighing of Risks and Benefits in Smoking Initiation
Halpern-Felsher and colleagues (Appendix E) also discuss other personal and behavioral factors that influence smoking behavior in adolescents, including the reasons adolescents smoke and how they weigh smoking pros and cons. According to Halpern-Felsher and colleagues, the motivation for adolescents to start smoking can result from a variety of factors: curiosity about a means to relieve stress and boredom, peer and social influence, parental influence, and as a means to decrease appetite or increase the intoxicating effects of alcohol and drugs (Conrad et al. 1992; Turner et al. 2006; Vuckovic et al. 2003).
Although adolescents tend to minimize the risks of smoking, they also have a tendency to exaggerate the benefits of smoking, especially given the influences of a variety of factors such as those mentioned above. One tool used to understand how perceived benefits motivate individuals to smoke, compared with how perceived risks deter smoking, is the Decisional Balance Inventory which incorporates a weighing of both the benefits (pros) and the risks (cons) in predicting behavior and behavioral change. The tool assesses three factors: social pros (e.g., kids who smoke have more friends), coping pros (e.g., smoking relieves tension), and cons (e.g., smoking stinks). Using this Inventory, Prokhorov and colleagues found that scores on the smoking pros scale increased and that those on the cons scale decreased, as adolescents were more susceptible to smoking (Prokhorov et al. 2002). Pallonen
also found a positive relationship between perceived smoking benefits and nonsmokers’ likelihood of smoking, whereas the cons of smoking were less predictive of smoking (Pallonen et al. 1998). Researchers have also noted that adolescent smokers tend to perceive that benefits are more likely to occur and that risks are less likely to occur compared with adolescents who have not smoked (Goldberg et al. 2002; Halpern-Felsher et al. 2004).
In summary, research suggests that adolescents misperceive the magnitude of smoking harms and the addictive properties of tobacco and fail to appreciate the long-term dangers of smoking, especially when they apply the dangers to their own behavior. When taken together with the general tendencies of adolescents to take a short-term perspective and to given substantial weight to peer influences, they tend to unduly discount the risks and overstate the benefits of smoking. These distorted risk perceptions are associated with adolescents’ decisions to initiate tobacco use, a decision that they will later regret.
ATYPICAL PATTERNS OF TOBACCO USE
The discussion has thus far focused on what may be regarded as the “standard” pattern of tobacco use. The typical case of tobacco addiction involves a person who began smoking as a teenager; rapidly escalated to daily use and to nicotine addiction; and eventually has a “smoking career” of 15 to 20 years of frequent daily use, characterized by heavy regret and punctuated by unsuccessful efforts to quit. In this section, the committee calls attention to patterns of smoking that deviate from this typical pattern (e.g., an increase in occasional, and perhaps non-addictive or less addictive, smoking to highlight the challenges that they pose for tobacco use prevention and control efforts).
One pattern of occasional smoking is nondaily smoking. Most smokers smoke cigarettes every day. Nondaily smoking was once thought to occur only in the first few years of initiation, before the development of nicotine dependence. However, research conducted since 1990 suggests that occasional smoking is becoming more frequent among U.S. smokers, whereas daily smoking is declining. A survey of 32 Minnesota work sites conducted from 1987 to 1990 found that 18.3 percent of smokers were nondaily smokers (Hennrikus et al. 1996). At follow-up two years later, 21.5 percent were nondaily smokers, suggesting that the rate of occasional smoking was increasing. Results from the Behavior Risk Factor Surveillance Survey (BRFSS) showed that the median proportion of “some-day” smokers among adults aged 18 years and older increased from 17.2 percent in 1996
to 24.0 percent in 2001 (CDC 2003). However, whether such an increase in nondaily smoking is occurring remains uncertain. Data from NHIS of individuals 18 years and older do not support this finding; the mean rate of some-day smoking remained fairly constant between 1993 (18.4 percent) and 2004 (18.7 percent) (CDC 2005a; Hyland et al. 2005).
Nondaily smokers among adults are younger, are highly educated, have higher income levels, are more likely to be racial and ethnic minorities (African American, Hispanic, and Asian) and male, and are more likely to have begun smoking after age 19 years (CDC 2003; Hassmiller et al. 2003; Husten et al. 1998; Hyland et al. 2005). About half of nondaily smokers had been regular smokers of 10 or more cigarettes per day in the past. Many more nondaily smokers than daily smokers reported a strong intent to quit smoking.
The rate of nondaily smoking varies widely by state. An analysis of nondaily smokers based on NHIS longitudinal data from 1996 through 2002 revealed wide state-by-state variations in the rate of nondaily smoking (as a proportion of all current smokers), ranging from 15.2 percent in Kentucky to 41.2 percent in Washington, D.C. (CDC 2003). From 1996 to 2001, the prevalence of nondaily smoking increased in 38 states. Nondaily smokers were more likely to be young and were slightly more likely to be men than women. The nondaily smoking prevalence was, in general, the highest in states or territories with the lowest overall smoking prevalence (such as California, Utah, and Puerto Rico) and the lowest in states with the highest smoking prevalence (for example, Kentucky and West Virginia).
Nondaily smoking may represent a transitional stage toward quitting for some smokers. In the 1990 California Tobacco Survey of smokers 18 years of age or older, 15.4 percent of smokers were classified as occasional smokers (smoking on some days but not every day and smoking on 25 days or less in the past month) (Evans et al. 1992). Two-thirds of these smokers were considered not to be in the process of taking up smoking based on their age (25 years or older). Twenty percent of occasional smokers had been daily smokers in the previous year, indicating that it is possible to switch from daily to occasional smoking. Furthermore, many of the occasional smokers were planning to quit within the next 6 months, suggesting that occasional smoking may be a transition to quitting (Evans et al. 1992).
Several explanations for an increasing prevalence of nondaily smoking have been proposed (CDC 2003). These include some tobacco control interventions that make it more difficult to smoke, such as smoking bans in public places and the increased price of cigarettes in recent years. Another explanation is that some nondaily smokers are still in the uptake phase of smoking or have previously been daily smokers who are in the process of trying to quit. The recent increase in initiation of smoking among individuals over 19 years of age may also contribute to the increased prevalence
of nondaily smokers. Individuals who start smoking at a later age perhaps become less dependent in general than those who start at a younger age.
Another atypical pattern of smoking that poses a quandary for tobacco prevention and control efforts is daily light smoking (i.e., smoking less than five cigarettes per day). Since 1993, data from NHIS show that the proportion of light smokers has increased from 2.9 percent in 1993 to 4.8 percent in 2004 (CDC 2005a). Although these light smokers (or “chippers”) may smoke daily, they do not develop nicotine dependence. They are, however, similar to dependent smokers on a number of parameters, including puff number and duration, as well as blood nicotine absorption and elimination levels. They also show cardiovascular responses similar to those of dependent smokers (Brauer et al. 1996; Shiffman 1989; Shiffman et al. 1990, 1992). These findings challenge classical theories of nicotine dependence (Shiffman 1989).
Studies that have examined the smoking attitudes and behaviors of smokers have also found perplexing similarities and differences between those of light smokers and those of dependent smokers. Presson and colleagues found that future chippers closely resembled future heavy smokers in viewing smoking as not very harmful to their health (Presson et al. 2002). Future chippers differed from heavy smokers, however, in that they had social environments with low levels of risk (i.e., low levels of smoking among peers and family members). Other studies have found that light smokers and heavy smokers tend to differ in their motives and attitudes toward smoking. Smoking behavior among light smokers tends to be influenced by social and sensory motives (the pleasure of handling cigarettes and smoking itself) rather than pharmacological or addiction-related reasons, such as cravings and habit (Shiffman et al. 1994). Notwithstanding the lack of classical nicotine dependence among low-level smokers, the scientific evidence on the harmful effects of exposure to low levels of nicotine (DHHS 2006) and the potential transitional nature of individuals in this subpopulation of smokers argue for focusing special attention on helping these individuals stop smoking.
POPULATIONS AT GREATER RISK OF CONTINUING SMOKING
A variety of individual and group characteristics and behaviors have been associated with higher rates of tobacco product use. Wallace (Appendix P) provides a review of some of these populations: adult smokers with mental illness, children and adolescents with mental illness and conduct disorders, inmates in correctional institutions, military recruits, homeless individuals, gamblers, and some individuals with disabling conditions.
Wallace notes that there have been a few recent national surveys suggesting that the majority of cigarettes in the United States are sold to per-
sons with a lifetime history of some type of psychiatric morbidity, but this needs additional confirmation (Breslau 1995; Breslau et al. 1991, 1993, 1994; Grant et al. 2004; Hughes et al. 1986; Lasser et al. 2000).
Children with psychiatric and behavioral comorbidities and adverse experiences are at risk for smoking initiation. Children with attention-deficit/ hyperactivity disorder (ADHD) were found to have a higher risk of cigarette use initiation and smoking maintenance, as well as abuse of other substances, than those in non-ADHD comparison groups (Daley 2004; Lambert and Hartsough 1998; Wilens et al. 1997). Wallace also notes that a body of literature has associated a host of adverse experiences—including direct physical or sexual abuse, the presence of depressive effect, suicide attempts, sexually transmitted diseases, and an impoverished, dysfunctional household environment—with substantially increased risks of smoking initiation (De Von Figueroa-Moseley et al. 2004; Dube et al. 2003; Mcnutt et al. 2002; Nichols and Harlow 2004).
Furthermore, Wallace notes that, although the research literature is not extensive, higher rates of smoking have been documented among incarcerated individuals, homeless individuals, and other populations. Among these populations, the highest rates of smoking have been reported among inmates. Hughes and Boland (1992) and Lightfoot and Hodgins (1988) reported a 77 percent smoking rate in the past 6 months among inmates in a penitentiary for men. High rates (71 percent) of current smoking have also been reported among women arrested in New York City (Durrah and Rosenberg 2004). The higher rates of smoking among prisoners may be influenced by the intersection of a number of other factors associated with higher rates of smoking, such as substance abuse, lower socioeconomic status, and high rates of psychiatric comorbidities among incarcerated individuals (Andersen 2004).
The literature describes a group of “hardcore” smokers who have never attempted to quit smoking. This subgroup of smokers is often described as a small but intractable public health problem. Using data from the 1998-99 Tobacco Use Supplement of the Current Population Survey, Augustson and Marcus (2004) defined “hardcore” smokers as established daily smokers (smoking for at least 5 years) who smoke more than 15 cigarettes per day with no reported history of quit attempts and who are over 25 years of age (Emery et al. 2000). They found that “hardcore” smokers represent 24.7 percent of heavy chronic smokers, 17.6 percent of all established smokers, and 13.7 percent of all current smokers. They are also more likely to be male, unmarried, not working, and to have lower education levels. Warner and Burns (2003) suggest that “hardcore” smokers represent members of a group of smokers whose behavior may be especially resistant to change (Warner and Burns 2003).
Genetic vulnerability may be one reason some “hardcore” smokers
find it difficult to stop smoking. Emerging genetic and pharmacogenetic studies have identified a potential role for gene variances in frustrated cessation attempts. One study, for example, found that smokers with a variant CYP2B6 gene have increased cravings for cigarettes following cessation and are about one and one half times more likely to relapse during treatment (Lerman et al. 2002). Information on genetic variants related to dopamine, serotonin, and nicotine metabolism, as well as other mechanisms that play important roles in nicotine addiction and maintenance, will be important to understand and better assist “hardcore” smokers and other smokers who have difficulty quitting.
There seems to be little doubt that a subset of the population of long-term smokers is more heavily addicted and less amenable to cessation inteventions. It is likely that these smokers are particularly vulnerable to nicotine addiction on the basis of predisposing personal characteristics and environmental stresses. These observations have two important implications: first, it is clear that specialized cessation interventions will be needed to assist them with quitting. Second, a realistic assessment of the prospects of achieving a substantial reduction in the prevalence of tobacco use must take the size of the “hardcore” target populations into account.
Smoking prevalence reflects the combined effects in any given period of the changes in the number of new smokers and in the number of smokers who have quit (Niaura and Abrams 2002). This chapter has provided an abridged overview of an extensive body of literature on the factors that affect the trends in smoking prevalence, with particular attention given to how the unique nature of nicotine addiction poses significant challenges to the success of tobacco control efforts.
At the center of the story emerging from this literature is the fact that nicotine addiction stimulates and sustains long-term tobacco use, with all of its serious health hazards and social costs. The literature also indicates that, although an overwhelming majority of smokers (90 percent) regret having begun to smoke, overcoming the grip of addiction and the associated withdrawal symptoms is difficult; most smokers must try quitting several times before they are successful. Progress in helping smokers who want to quit and achieve successful and permanent cessation requires that a variety of cessation technologies, both clinical and population-based, be readily available to the smoking population, that they be used, and that they be effective. This task is discussed further in Chapter 5 of this report.
While tackling the difficult challenge of helping addicted smokers quit, the fact that thousands of individuals begin smoking each day must also
be addressed. Most of these new smokers are youth and adolescents who, in part because of their developmental stage, do not clearly understand the full range of risks and consequences of smoking or who discount these long-term health risks because of a belief that they do not apply to them personally.
These distortions of judgment include a failure of youth and adolescents to appreciate the risk and grip of addiction when they begin smoking. Tolerance and dependence to nicotine can occur early on after initiation (Bottorff et al. 2004; DHHS 1994; DiFranza et al. 2000; IOM 1994), and the early initiation of smoking is related to the number of years that a person will smoke and the quantity of cigarettes smoked per day in childhood. Less is known about initiation and subsequent intensity after adolescence (Escobedo et al. 1993; Taioli and Wynder 1991). Unfortunately, many youths view themselves as invulnerable to addiction and its associated harm. They are also sensitive to the social factors and norms that promote smoking, such as the influences exerted by peers, family members, and the exposure to smoking in the media. These influences tend to override the information about the risks of smoking. Therefore, to substantially reduce the rate of smoking initiation, it will be necessary to do a better job of counteracting the perceived benefits of smoking and to develop new tools that make the personal risks of starting to smoke more salient.
All new smokers are not young, however. Some initiate smoking during their college years, which helps to explain why some new smokers have characteristics that differ from those of usual smokers: they tend to have higher levels of education and income than other smokers. It is also noteworthy that some new smokers smoke at lower levels, and some never reach a level of dependence. It will be important for tobacco control experts to pay close attention to these emerging trends and to design appropriate interventions to respond to them.
On the other side of the ledger are smokers who have a more difficult time quitting. “Hardcore” smokers with a long career of smoking and individuals with psychiatric comorbidities or special circumstances, including incarceration and homelessness, have not been the primary targets of traditional cessation treatments or research studies. Achieving success in substantially reducing tobacco use will require taking stock of the progress made with current tobacco prevention and control strategies, identifying where they fall short in responding to emerging smoking trends, and identifying the characteristics and behaviors of subpopulations of smokers. Success will also require the rigorous implementation of known, effective strategies and pushing the envelope to develop new and innovative approaches that can build on the existing tools and strategies used to help people quit smoking.
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