Publications : Books : Nicotine Addiction in Britain :

5 The natural history of smoking: the smoker's career

*5.1 Nicotine intake in novice smokers, and the development of dependence
*5.2 Persistent and compulsive smoking in the face of smoking related ill-health
*5.3 Non-dependent smokers
*5.4 Smoking cessation rates in Britain
*References

5.1 Nicotine intake in novice smokers, and the development of dependence

The vast majority of people who become regular smokers begin their smoking career in adolescence. It is currently difficult to assess dependence on nicotine at this age because the available standard instruments and criteria for measuring and determining dependence have been developed primarily for adults. They do not necessarily therefore take account of the special constraints on smoking that apply to young people, such as not being able to smoke at home or at school, or of the financial and legal limitations on the availability of cigarettes at this age. There are as yet no agreed specific criteria for defining and diagnosing nicotine dependence in young smokers. Some preliminary research has been carried out with older teenagers in the US and New Zealand (summarised below). In addition, small-scale studies and national surveys of young people's smoking in England have sometimes included saliva cotinine measurements; the findings of these in relation to the development of dependence are also discussed.

Measuring nicotine dependence in adolescents

In the US, Prokhorov et al1 modified the Fagerström Tolerance Questionnaire (FTQ) for use in a group of over 100 vocational technical students aged 15-20 years (an atypical sample shown to be more likely to start smoking earlier, and to smoke more heavily than their high school counterparts). Although there were marked differences in cigarette consumption and duration of smoking relative to adult populations, the overall FTQ was close to that of a sample of highly nicotine-dependent adults. The FTQ values were generally lower in the student sample, but 20% had an overall FTQ score of 6 and above (compared with 49% in the adult sample), consistent with substantial nicotine dependence.

In New Zealand, using the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IIIR classification of dependence,2 20% of a sample of 900 18 year olds were found to be dependent on tobacco. Among those who had smoked every day for a month in the last year, 56% were classified as tobacco dependent.

Inhalation and nicotine intake

Several UK studies have demonstrated that evidence of smoke inhalation and nicotine intake is demonstrable from saliva cotinine concentrations from a very early stage of smoking.3-5 In a study of 11-15 year old girls in London,3 cotinine concentrations in occasional smokers (non-daily smokers) indicated that some were already inhaling and obtaining pharmacologically significant doses of nicotine from their cigarettes. By the time a girl was smoking on a daily basis, she appeared to be inhaling a similar dose of nicotine per cigarette to that inhaled by adult smokers.

The Health Survey for England measured salivary cotinine in over 10,000 4-24 year olds in 1996 and 1997. Analyses of these data5 also demonstrate that inhalation is established even in non-daily smokers. Almost all those claiming to smoke more than six cigarettes a week had cotinine values of 15 ng/ml or above, which is strongly indicative of smoking.6 For those claiming to smoke between one and six cigarettes a week, 82% of boys and 84% of girls had cotinine values above this level. Cotinine is sensitive to recency of smoking, so the authors concluded that it was likely that the saliva sample was taken after a gap of several days since the last cigarette in the rest of the group. Cotinine levels were higher in the lower income groups, indicating greater exposure to smoke constituents and hence risk of smoking related disease being established in these groups at a young age.

Cotinine levels among smokers increase with age. Given the early establishment of inhalation, it seems likely that these increases are largely due to increases in cigarette consumption rather than to increases in the amount of smoke inhaled per cigarette.3

Quit attempts and withdrawal symptoms

The development of inhalation means that nicotine can play an active role in reinforcing smoking from very early in the smoker's career. Consistent with this, studies have also shown that the majority of young smokers perceive themselves to be dependent on smoking. In the study of London schoolgirls,7 even within their first year of smoking most reported wanting to stop, having tried to do so, and suffering aversive effects when doing so. Daily smokers were more likely to report withdrawal effects than non-daily smokers (74% vs 47%). A withdrawal score measured in this study correlated significantly with saliva cotinine levels and weekly cigarette consumption. It seems likely that withdrawal effects would be partly responsible for the failure of attempts to stop.

A recent national survey of teenagers and smoking in 1997 in England8 supported these findings. Nearly half (49%) of the current smokers said they would like to give up smoking, and 71% of them reported that they had tried to quit. Nearly half (49%) of regular smokers (defined as usually smoking one or more cigarettes a week) also said they would find it difficult to go without smoking for a day, and 22% that they would find it very difficult. Only 4% of occasional smokers (defined as less than one cigarette a week) said they would find it difficult. Conversely, only 20% of regular smokers said they would find it very easy not to smoke for a day, compared with almost three-quarters (73%) of occasional smokers. The authors concluded that although, on average, children smoke fewer cigarettes than adults, the relative proportions of the regular smokers reporting different degrees of perceived difficulty were comparable to those reported in surveys of adult smokers.

Similar findings have been reported elsewhere.9 In a US survey of 12-18 year olds10 the likelihood of reporting symptoms of nicotine withdrawal increased in relation to frequency and intensity of cigarette smoking. Younger and older smokers were equally likely to report increasing nicotine withdrawal symptoms as smoking frequency increased.

Sargent et al11 examined smoking cessation in 12-18 year old adolescent smokers in the US. They found that smoking cessation rates were 46% among occasional smokers, 12% among daily smokers of 1-9 cigarettes, and 7% of those smoking 10 or more cigarettes per day. The authors reported that this latter rate was comparable with that observed in addicted adult smokers. Although intent to quit smoking was a reliable predictor of cessation among occasional smokers, this was not the case among the adolescent daily smokers, suggesting that nicotine addiction had become important in maintaining cigarette smoking in smokers in this age group.

It is not yet clear how relapse in adolescents compares with adults,11 or even whether the concept of relapse is applicable to teenagers. Some studies found relapse rates of a lower order among adolescent than among adult quitters, whereas other studies found adolescent quitters to be more likely than adults to relapse. This is an area requiring further research. The difficulty experienced by many adolescent smokers in giving up smoking demonstrates the need for cessation support for this age group.

Time to the first cigarette of the day

How soon people smoke their first cigarette after waking is another measure of addiction. In the 1997 English survey of adolescents,8 just under half (46%) of the regular teenage smokers usually had their first cigarette within an hour of waking up in the morning, boys being more likely than girls to do so (53% vs 41%). Barton concluded that this was fewer than the percentage of adult smokers who smoke within an hour of waking (64%) (although still high), and could be accounted for by the fact that many children and adolescents cannot smoke at home. Only 13% of regular adolescent smokers usually smoked their first cigarette within 15 minutes of waking, compared with a third of adults.

Subjective effects

Subjective effects of smoking are also commonly reported by adolescent smokers,8,12 and there is some evidence of consistency in reports of these effects over time.13 In the British survey,8 77% of current smokers said they felt calmer after smoking, 28% felt dizzy, 23% felt more alert and 6% felt sick. Regular smokers were more likely than occasional smokers to feel calmer after smoking (84% vs 62%) and less likely to feel dizzy and sick.

The nature of any positive reinforcement that children get from their smoking is unclear. In the London study,12 less than a quarter reported a nice feeling from their smoking, suggesting that such positive pleasant feelings were not critical to their smoking. Again, the most prominent subjective effect was feeling 'calmer', and there was a significant correlation between this and saliva cotinine concentrations. This feeling was also related to reports of aversive withdrawal during attempts to stop. Rather than a direct effect of their smoking, feeling calmer may therefore come about as a relief of incipient withdrawal symptoms. The relationship between feeling calmer when smoking and reports of aversive effects when attempting to give up was evident even among those in their first year of smoking, suggesting a rapid development of dependence. There was also some evidence that these effects became more pronounced with more prolonged exposure to smoking.

Gender differences in dependence

Goddard4 investigated whether sex had an effect on dependence, independent of amount smoked. She developed a composite model of dependence based on questions about craving, difficulty going without smoking, perceived difficulty in giving up smoking, and likely success in quitting. Usual cigarette consumption was the strongest predictor of dependence, with cotinine levels also having a significant effect. Sex was much less important than consumption in predicting dependence, but the analysis indicated that girls appeared more likely to be dependent on cigarettes than boys at a given level of consumption.

Initial smoking experiences

It is known that tolerance can begin with the first dose of nicotine.14 Very few studies have examined the effects of the first few cigarettes;15,16 this is an area requiring further research. It is thought that the interpretation of the effects of the first cigarette may be important.17

Progression from experimental to regular smoking

Experimental smokers are highly likely to become regular smokers,18 but exactly what proportion goes on to regular smoking and what factors influence this progression remain largely unknown. It has been argued19,20 that smoking only a few cigarettes leads to a near inevitable escalation to regular smoking. Other more recent studies have indicated that perhaps one-third to one-half of those young people who experiment with cigarettes go on to become regular smokers.13 Studies do indicate considerable movement into and out of smoking behaviour over the first few years of smoking. One study, however, found that daily smoking was particularly stable over a two-year period, since 97% of daily smokers in the first survey were still smoking two years later.13

Conclusions

All the above studies support an early development of dependence on nicotine in young smokers. Daily smokers appear to be inhaling similar doses of nicotine per cigarette to those inhaled by adults, and are highly likely to want to quit, to have tried to quit, and suffered withdrawal effects when doing so. However, even in many more occasional smokers, inhalation is apparent and there are perceived difficulties in quitting. What can we therefore conclude about the onset of nicotine dependence and models of the development of smoking behaviour?

The development of a regular smoking pattern had been reported to take about two years and was envisaged to involve a progression through a series of stages. Flay et al21 postulated a four-stage model:

  • preparatory stage
  • trial stage
  • experimental stage, and
  • regular smoking.

Another model suggested that young smokers may move from initial use, motivated by non-pharmacological factors, to later use, motivated by relief of withdrawal or by other reinforcements due to the pharmacological properties of nicotine.22 In general, the suggestion is that nicotine gradually takes a stronger hold over time.
Pomerleau et al23,24 have suggested a 'sensitivity' model in contrast to the above 'exposure' model of tolerance. This suggests that vulnerability to nicotine dependence is related to high initial individual sensitivity to nicotine. They argue that initial exposure to nicotine in individuals who have high innate sensitivity produces more intensive reinforcing effects, and that nicotine exposure for these people quickly leads to the development of tolerance and dependence. Individuals less sensitive to nicotine initially may experience less intense effects from nicotine and will not continue to smoke because they are less responsive to its reinforcing effects.

The validity of the stage models has not yet really been established. For some girls in the London study,3 daily smoking seemed to develop much more quickly than previously envisaged. Approximately half of those who took up smoking during the study were smoking on a daily basis within one year. It is possible that the two models may both be appropriate, and that different sensitivities to nicotine may produce different developmental patterns and determine the rate at which a teenage smoker moves through the stages. Further research is needed in this area.

5.2 Persistent and compulsive smoking in the face of smoking related ill-health

As discussed in chapters 3 and 4, the majority of adult smokers state that they would like to stop smoking, and indeed many have already tried unsuccessfully to quit. Some may take the view that such intentions to quit can be half-hearted in people who may not yet have any serious smoking-related illness or perceive themselves as having any immediate risk. This view would suggest that, if we really want to see how addictive smoking is, we should examine the smoking behaviour of smokers diagnosed as having a condition known to be caused or adversely affected by smoking, and who are aware that continued smoking will worsen that condition. This section will summarise the evidence on smoking cessation in such circumstances.

Cardiovascular disease

Smoking substantially increases the risk of cardiovascular disease. For example, smokers are almost twice as likely as never-smokers to suffer fatal ischaemic heart disease and four times as likely to suffer a fatal aortic aneurysm.25 Among smokers with an existing cardiovascular illness, smoking cessation slows disease progression and reduces the risk of recurrence. For example, smoking cessation reduces the risk of recurrence or premature death by about 50% in people with diagnosed coronary heart disease.26

The evidence suggests that, despite widespread awareness of the effects of smoking on their disease, and sometimes despite the provision of well designed smoking cessation interventions by health professionals for these people, the majority of smokers who develop cardiovascular disease are still smoking a year later. For example, in a large trial of patients undergoing coronary artery bypass surgery, only about a third of smokers had succeeded in stopping smoking at 10 years after medical or surgical intervention.27 One recent UK study28 assessed smoking cessation one year after patients were newly diagnosed with myocardial infarction (MI) or angina. Only 20% of 169 patients smoking in the two weeks prior to diagnosis had managed to quit smoking a year later, despite support by trained nurses and an average of more than two quit attempts by these patients throughout the year. Numerous studies have examined the effects of smoking cessation interventions in cardiac patients. Although some have found some beneficial effects of such interventions (when compared to 'usual care' controls), the long-term success rates are invariably well short of 50%.29,30

Certain forms of peripheral vascular disease are particularly closely associated with tobacco smoking. Buerger's disease is a progressive inflammatory occlusive disease almost exclusive to smokers, which commonly requires surgical intervention including limb amputation. Prognosis for Buerger's disease is considerably improved by stopping smoking.26 One recent study followed a cohort of 69 such patients over the first 10 years after diagnosis.31 All but one of the patients were smokers at the time of diagnosis, and 84% continued to smoke thereafter. Among those who continued to smoke, 65% subsequently required amputation, almost twice the percentage of those who stopped smoking.

Thus, although the onset of cardiovascular problems such as MI or angina initiates an increase in motivation and attempts to stop smoking, it is clear that the immediacy of the health risks is still not sufficient to enable most smokers to succeed in giving up.

Cancer

Tobacco smoking is associated with an increased risk of both respiratory and non-respiratory cancers. For example, lung cancer is approximately 20 times more likely in men who smoke than in never-smoking men, whilst pancreatic cancer is twice as likely in smokers than in never-smokers.25 Smoking cessation reduces the risk of developing cancer, the severity and progression of premalignant histological changes in the organs such as the lung and the cervix26 and the risk of further neoplasms, and it improves survival rates in patients who have cancer.26,32

Studies of smoking cessation following cancer diagnosis face the problem that some patients who believe their illness to be terminal may perceive no advantage to stopping smoking. Others may have been prevented from smoking by the severity or circumstances of their illness both before and after diagnosis. There are also problems related to underreporting of smoking by patients. Studies of smoking cessation in patients with lung cancer typically find that about 40% have succeeded in stopping smoking by two years after diagnosis and lung resection.33 Some studies using specially designed smoking cessation interventions have found one-year abstinence rates as high as 60% in head and neck cancer patients,34 but others have found that only 21% remain abstinent six weeks after the intervention.35 Although the diagnosis of a smoking related malignancy clearly represents a strong catalyst for smoking cessation, it is however a consistent finding that a sizeable subgroup of patients (generally more than one-third) continue to smoke despite attempting to quit.36

Respiratory disease

Tobacco smoking is a major cause of a large number of respiratory illnesses, including chronic obstructive pulmonary disease (COPD).25 The impact of smoking cessation on the progression of COPD was assessed definitively in the landmark Lung Health Study.37 This study aimed to assess whether an intensive smoking cessation intervention and the use of a bronchodilator could slow the rate of decline in lung function in otherwise healthy smokers who already had detectable, but mild, impairment of lung function. Almost 6,000 middle-aged smokers were randomised to receive an intensive smoking cessation intervention plus a bronchodilator inhaler, the cessation intervention plus placebo inhaler, or no intervention. All participants were required to be smokers of at least 10 cigarettes per day, be willing to consider smoking cessation, and to participate in a five-year follow-up. The sample recruited had actually smoked an average of over 30 cigarettes per day for over 30 years. The smoking cessation intervention used was one of the most intensive ever evaluated in a large trial,38 and included 'aggressive' encouragement to use (free) nicotine gum. The cessation rates achieved with this intervention were among the highest reported in a major trial, with 35% of the intervention group being abstinent at one year, compared with 9% in the non-intervention group. At five years, 22% of the intervention group were still not smoking, compared with 5% of the control group.

The high cessation rates found in this study are partly attributable to the careful screening of participants, which ensured that the study population was highly motivated to give up (as shown by the high cessation rate in the control group). However, even with this intensive intervention in motivated patients, the fact remains that more than 75% of smokers with established early COPD were still smoking five years later. Studies involving unselected patients with respiratory disease in Britain have tended to find one-year smoking cessation rates of under 10%,39-41 and that cessation rates in patients with respiratory disease tend to be lower than in those with cardiac disease.40

Smoking cessation in hospital patients

The relatively low cessation rates (<10%) in the British studies described above39-41 suggest, contrary to what might be expected, that patients with smoking related diseases are no better than other patients or non-patients at stopping smoking. Some studies have actually found that patients with smoking related diseases are less successful at stopping smoking than other types of hospital patients.42 Consistent with this, patients in the Lung Health Study with more respiratory symptoms at baseline were less likely to succeed in stopping smoking.43

Recent trials of specially designed interventions for hospitalised patients have achieved one-year abstinence rates as high as 27%,44 although it is noticeable that in such studies the one-year biochemically confirmed abstinence rates in the control (usual care) groups were often below 10%.45

Pregnancy

The other condition in which smokers have a clear and immediate reason for stopping smoking is pregnancy because smoking in pregnancy damages the fetus (see Section 1.4). Despite widespread awareness of the adverse health effects of smoking during pregnancy, only one in five women in the UK who are smoking when they discover they are pregnant manage to stop smoking during their pregnancy.46 Even when specially designed smoking cessation interventions are provided, this leads at best to only an additional 10% of women stopping smoking while pregnant.47

Conclusions

The evidence reviewed in this section demonstrates that the onset of certain conditions such as lung cancer, a heart attack or pregnancy provides the motivation for a higher proportion of smokers to try to succeed in stopping smoking than would otherwise have been the case. However, even after developing a serious smoking related illness which threatens loss of life or limbs in the immediate future, the majority of smokers are unable to stop smoking completely in the year after their condition is diagnosed. This remains true when medical advice and nursing support are provided, and when the smokers make determined attempts to stop smoking. When considered in conjunction with the other available evidence on the role of nicotine in tobacco smoking, this provides convincing evidence that many smokers suffer serious ill-health not through personal choice, but because they are, and remain, dependent on the nicotine they obtain from tobacco.

5.3 Non-dependent smokers

In 1976, Zinberg and Jacobsen48 used the term 'chippers' to refer to opiate users who were capable of controlling and limiting their use of opiates, as opposed to the common pattern of escalating and compulsive opiate use which many had come to associate with heroin users. Their paper is one of many in the drug addiction field which recognises that drugs which have strong dependence-producing qualities in many people do not necessarily produce dependence in all users.49
Since those early studies of non-dependent heroin users, it has been recognised that not all tobacco smokers progress to become highly dependent chain smokers. Shiffman, in the US, was one of the first to study systematically the phenomenon of non-dependent smokers, and he also used the term 'chippers'.50 This section will summarise what is known about non-dependent smokers.

Definition and prevalence of non-dependent smoking

The question of what proportion of smokers is dependent is not as simple as it might at first seem to be. Degree of dependence is best conceptualised as existing on a continuum, rather than as a dichotomous variable (dependent vs non-dependent). Central to the definition of dependence is the perception of some compulsion to smoke and a sense that it would be difficult to abstain. There is good evidence that the degree of dependence (when defined as difficulty in abstaining) is closely related to the frequency of smoking.51 In the UK, almost 58% of current smokers state that they would find it very or fairly difficult to go without smoking for only one day. People smoking 20 or more cigarettes per day are more likely to say it would be difficult than those smoking less than 10 a day (83% vs 23%).52 The proportion of non-dependent smokers is therefore related to the definitions both of 'a smoker' and of 'dependence'.

There appears to be a consensus in the literature that adults who consistently smoke five or fewer cigarettes per day (but who smoke on at least four days per week) over a long period (eg more than a year) are non-dependent. Although cross-sectional surveys find that up to 20% of UK smokers report smoking fewer than five cigarettes per day,52 it is unclear what proportion of these people are in a transitional phase of increasing or decreasing consumption. One study in Australia found that only 8% of 700 adult smokers smoked five or fewer cigarettes per day.53 However, most of these were preparing to quit smoking, and so may have been reducing their consumption. It has been estimated that only about 5% of smokers are able to smoke without becoming addicted.54

The first studies of tobacco chippers compared them to samples of heavy smokers (20-40 cigarettes per day). The light smokers reported no signs of nicotine withdrawal after overnight abstinence and, in contrast to heavy smokers, also reported that they could regularly and easily abstain from tobacco for periods of a few days or longer.50 This confirms that they were at the low end of the dependence continuum. However, it was also found that the chippers' nicotine absorption per cigarette and nicotine elimination rates were similar to those of heavy smokers.55,56 The chippers were less likely both to smoke to relieve stress and to report an aversive response to their first ever cigarette. The light smokers also reported having fewer smoking relatives.

A UK study compared very light smokers (consistently less than six cigarettes per day) with regular smokers in a cohort of women followed up for a year.57 This study found that very light smokers had higher educational attainment, more non-smoking relatives, but also more very light smokers among their relatives, lower neuroticism scores, and were less likely to state that they smoked to help them cope.

It has been suggested that vulnerability to nicotine dependence is related to genetically based high initial sensitivity to nicotine.23 Consistent with this, people who become highly dependent cigarette smokers have been found to have more pleasurable sensations at their initial exposure to tobacco.58 It has also been reported that regular smokers recalled more unpleasant reactions to their first cigarette than chippers.54 Another study found that initial dizziness predicted increased likelihood of rapidly progressing to further smoking in children.15

Conclusions

A small proportion of smokers (probably about 5%) are able to maintain regular, but low levels of tobacco consumption and periods of abstinence with little difficulty. It is not clear why this is the case for some but not for the majority, but some available evidence is consistent with a constitutionally reduced sensitivity to nicotine. The existence of tobacco chippers does not imply that nicotine is non-addictive, any more than the existence of opiate chippers implies that heroin is non-addictive.

5.4 Smoking cessation rates in Britain

Cigarette smoking is a chronically relapsing behaviour. It is clear that many who have sustained long periods of abstinence go back to smoking. From an increasing group of cessation trials with long-term follow-up we know that relapse rates among those initially succeeding decline over time, but still remain substantial for some years: about 50% of those abstinent for six weeks relapse by six months, and 20% of those abstinent for six months relapse by one year.59 There is also evidence that 30-50% of those abstinent for one year will relapse before five years.60,61

It might be tempting to think that such trial data give a pessimistic view of relapse because their populations include more dependent smokers, frequently with a long history of failure. However, at least one major population survey recording retrospective reports of periods of abstinence supports these results, giving a figure of 35% relapse after one year of abstinence.26 The same survey suggests that an asymptote in relapse rates may be reached after about five years of cessation - but until an ex-smoker dies there can be no certainty that he or she has 'quit for life', which makes it extremely difficult accurately to calculate lifetime cessation rates at any one point in time.

The 'annual cessation rate' is the percentage of regular smokers in a population who quit each year and remain abstinent. It can be aggregated over a long period to estimate the 'lifetime cessation rate': that is, the percentage of ever-smokers who stop and stay stopped. These statistics, together with the rate of smoking uptake among never-smokers, broadly define the dynamics of smoking prevalence. Unfortunately, there are few prospective studies of the natural history of smoking within individuals to allow these rates to be estimated reliably in the British population, but existing cross-sectional data collected repeatedly over time in the General Household Survey (GHS)52 can be used to provide estimates of cessation rates.

Figure 5.1 shows the cross-sectional smoking prevalence curves plotted by age for the 13 surveys containing smoking data between 1972 and 1996. There are two striking features in these data:

  1. The curves demonstrate a consistent trend for smoking prevalence to fall within the older age groups. The only major exception is the curve for 1996, which shows stable or increasing prevalence at all ages.
  2. There is no evidence of a similar trend towards reduced prevalence over time in those under the age of 25, since the prevalence curves for this age group are tightly clustered from 1982 onwards. As discussed in Section 1.2, this reflects the fact that smoking prevalence in younger people has been stable or increasing in recent years. Very few people start smoking after the age of 25, so it is reasonable to infer that until the early 1980s the declining prevalence in Britain was due, at least in part, to falling rates of uptake of smoking, but that the decline since then is attributable primarily to the loss of prevalent smokers through smoking cessation or death.

Fig 5.1. Prevalence of cigarette smoking in Great Britain by age, 1972-1996 52

Estimation of annual cessation rates

There are several options for estimating annual cessation rates over time from the GHS cross-sectional surveys, although none is ideal. One method is to calculate cessation rates directly as the percentage of those who have ever smoked who now regard themselves as ex-smokers. This ratio has been used extensively in the past, but may be subject to inaccuracies in respondents' classification of themselves as ex-smokers.62

An alternative approach is to follow the smoking prevalence among members of a particular age cohort as they are sampled by the GHS over time. Few people start smoking beyond the age of 25, few regular smokers quit before the age of 25, and the excess mortality from smoking does not have its most substantial impact until after the age of 60, so relatively reliable estimates of cessation rates can be obtained for those in the age range 25-59 years. Smoking cessation in this population is particularly important from a public health perspective, because quitting during this time enables a large proportion of the life-years to be saved that would otherwise be lost by continued smoking.63

Those aged 25-49 in the 1986 survey were sampled again by the GHS at the age of 35-59 in the most recent survey in 1996-1997. Figure 5.2 shows their estimated cigarette smoking prevalence at the two time points. Prevalence fell from about 36% to 28.8% over the 10-year period, indicating a long-term net reduction in smoking, after allowing for relapse. Assuming that the cessation rate remained constant over this time, the 7.2% (95% confidence intervals (CI) 5.7-8.7) reduction equals an annual cessation rate of about 2.2% (95% CI 1.7-2.8). The rate was similar for men (2.4%) and women (2.0%). It was lower for the younger group, aged 25-34 in 1986 (ca 1.4% per year), and higher for the older group, aged 35-49 in 1986 (ca 2.6%). Over the 10-year period, 20% of those aged 25-49 in 1986 gave up smoking cigarettes long-term, possibly for life.

A similar approach can be used to estimate cessation during the previous 10 years, 1976-1986. In 1976, the smoking prevalence among those aged 25-49 was 46.8%; by the time they were aged 35-59 in 1986, it was 35.6%. The 11% reduction equals an annual cessation rate of about 2.7%, suggesting that cessation rates were higher during this earlier period than in the last 10 years. Between 1976 and 1986, 24% of smokers in this age cohort gave up.


Fig 5.2. Prevalence of cigarette smoking in those aged 25-49 in 1986 and 35-59
in 1996. 63 Error bars give approximate 95% confidence intervals.

These estimates do not take into account any smokers who switched from smoking cigarettes to cigars, and who will be misclassified as ex-smokers in this analysis. Switching from cigarette to cigar smoking tends to occur primarily in men, so this effect may have contributed to the greater cessation rate observed in men relative to women, but in absolute terms the effect is likely to be very small. The prevalence of cigar smoking in people who have switched from cigarettes has also remained fairly constant in this population, so adjusting for this effect would have little influence on overall cessation estimates.

Cessation before the age of 60

Those aged 25-34 in 1972 can be followed until they were aged 50-59 in 1996-1997 to estimate total cessation before the age of 60. Cigarette smoking prevalence in this population fell from 53% to 27% over the 25 years, suggesting that 49% stopped before the age of 60. This estimate is possibly inaccurate because it does not allow for permanent switching to cigars or the fact that the majority were not followed until the age of 60, but it is in close agreement with previously published figures indicating that only about 50% of smokers stop smoking long-term before the age of 60.62

Conclusions

In the last 10 years, long-term cessation rates among middle-aged smokers have averaged around 2% per year, ranging from about 1.4% to 2.6% with increasing age. This is somewhat less than the 2.7% per year estimated for the previous 10 years, suggesting that cessation has been slowing. Over the last 25 years, about 50% of smokers have stopped smoking before the age of 60.

Overall, the evidence in this chapter demonstrates that in most smokers, dependence on nicotine is established during adolescence, and in many cases probably occurs before reaching the legal minimum age for the purchase of cigarettes. Once dependence is established, the majority of smokers will then continue to smoke for nearly 40 years. Experimentation with cigarettes in adolescence clearly has major long-term implications for individual and public health.

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Contents

Contributors, Foreword and Key Points
1  Tobacco smoking in Britain: an overview
2 Physical and pharmacological effects of nicotine
3 Psychological effects of nicotine and smoking in man
4 Is nicotine a drug of addiction?
5 The natural history of smoking: the smoker's career
6 Regulation of nicotine intake for smokers, and implications for health
7 The management of nicotine addiction
8 Regulatory approaches to tobacco products in Britain
9 Summary and recommendations

This page last updated on May 4, 2001