What proportion of smokers become addicted?

Most people who become smokers initiate smoking before the age of 18. They generally try smoking as part of experimentation, after observing their peers and family smoking and viewing tobacco advertising. It is fairly natural, when cigarette smoking can be observed so widely, for a child to think, “I wonder what that is like?”. Most kids who try smoking are not considering or expecting that they may become addicted. But it may be worth educating young people on their risks of becoming addicted. To do so we have to be clear about what we mean by “addiction”.

Nowadays the words “dependence” and “addiction” are generally used interchangeably with the same meaning. When used in relation to substance or drug use, these words refer to a situation in which the drug has come to unreasonably control a person’s behavior. The central characteristic of most definitions of drug addiction is that the individual experiences an impaired ability to reduce or end their use of the drug. In the case of cigarette smoking that characteristic is most commonly expressed as long term daily smoking despite awareness of the likelihood of serious health effects, a desire to reduce or quit, and failed attempts to reduce or quit.

In order to more clearly define, diagnose and study nicotine dependence, various diagnostic criteria have been developed, such as those of the American Psychiatric Association (DSM-IV) or the World Health Organization (ICD-10). These typically describe a list of criteria and require individuals to meet a certain number of these to meet the diagnostic threshold for “nicotine dependence”. There are 7 main DSM-IV criteria, (including things like difficulty cutting down, continued use despite it causing problems, experience of withdrawal symptoms when reducing etc) and if a smoker meets at least 3 of these they are considered to be “nicotine dependent”. Of course there is a certain artificiality about this because most people consider that nicotine addiction exists on a continuum of severity, rather than being a categorical disorder that a person either does or does not have. But these diagnostic frameworks at least give us a way of identifying those who are clearly addicted.

Last year, Drs Eric Donny and Lisa Dierker published a paper (in the journal, “Drug and Alcohol Dependence”) that aimed to identify what proportion of smokers in the general population met strict DSM-IV criteria for nicotine dependence. Their study was based on direct interviews with a large, representative sample of non-institutionalized adults in the United States in 2001-2. From that sample they focused on the 8,213 who were daily smokers in the past year. This sample included people who smoked anything from 1 to over 40 cigarettes per day, and people who had smoked for less than one to over 50 years.

The study found, not surprisingly, that the greater the number of cigarettes per day the person smoked, the greater the chance that they would meet strict diagnostic criteria for having become nicotine dependent. Whereas under 50% of those who smoked 1-5 cigarettes per day met the criteria, over 80% of those who smoked over 30 cigarettes per day met the criteria.

Unexpectedly, however, the longer the person had smoked, the less likely they were to have become dependent, particularly if the person had started smoking over 50 years ago. This finding seems very odd, and may have more to do with memory for quit attempts or attitudes to smoking among older age cohorts.

Overall, over 60% of ever daily smokers met strict diagnostic criteria for having become nicotine dependent. But almost all smokers had experienced at least one symptom of nicotine dependence. For example, 97% of “dependent” smokers had experienced difficulty cutting down their cigarette consumption, as had 72% of “non-dependent” smokers. The authors acknowledged that the differences in dependence between these two groups may be more quantitative rather than qualitative. The authors also acknowledged that certain co-occurring factors appear to make it more likely that a smoker will bcome dependent. An example they provided was a history of major depression, which is associated with approximately 100% nicotine dependence among heavy smokers.

So we can tell young people that if they take up smoking, there is an over 90% chance that they will experience some symptoms of nicotine addiction, and over a 60% chance that they will go on to meet strict diagnostic criteria for becoming addicted to nicotine.

A pdf copy of the full paper by Drs Donny and Dierner can be accessed (near the bottom of the page) at:
http://www.tern.org/Publications.htm

Labels: addiction, cigarette, cigarette smoking, dependence, jonathan foulds, nicotine

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Two new studies of Chantix (varenicline)

Two new trials of the smoking cessation medicine varenicline (Chantix) were published this past weekend. One reported the results in 515 nicotine-dependent Japanese smokers (mainly men) and the other reported the results in 250 Korean and Taiwanese smokers.

The Japanese study compared the outcomes across various doses of varenicline, with participants taking the pills for 12 weeks, and then being followed up for a further 40 weeks off drug. As in previous studies, the 1mg dose (twice daily) achieved slightly higher quit rates than lower doses, albeit with higher reported side-effects. The 1mg dose achieved abstinence rates of 65% at 12 weeks, as compared with 40% among those using placebo pills. At one year follow up, 35% of those who were given 1mg pills for the first 12 weeks remained abstinent, compared with 23% of those who had taken placebo pills. So this study in Japan confirmed the safety and efficacy of Chantix, but the “effect size” – the degree to which the drug performed better than placebo, was not quite as impressive as previous studies. This was partly because a relatively large proportion of Japanese smokers in this study succeeded in quitting while using placebo pills.

Another study based in Korea and Taiwan directly compared 12 weeks of 1mg varenicline with 12 weeks of placebo in 250 smokers (mainly men). After 12 weeks, 60% of those using varenicline were not smoking, compared with 32% of those using placebo pills. After 24 weeks (i.e. another 12 weeks “off drug”) the quit rate was 47% among those who had used varenicline, versus 22% among those who had used placebo. As in previous studies, those taking varenicline were more likely to report some nausea, constipation and abnormal dreams, but these were generally mild in nature. Also like prior studies, those on Chantix were not less likely to report an increased appetite. This is noteworthy as most previous smoking cessation medicines (such as nicotine replacement therapy or bupropion) tend to reduce appetite compared with placebo, and suggests that Chantix works via a slightly different mechanism.

So far, the placebo-controlled trials of varenicline have been remarkably consistent in finding that it approximately doubles quit rates compared with placebo, and that this increased quit rate is maintained even after up to 40 weeks off drug. The early studies suggested that Chantix may result in higher quit rates than other pharmacological treatments for smoking. Whether this ultimately turns out to be the case will require additional studies directly comparing different treatments.

The take-home message for smokers interested in trying to quit is that this new medicine continues to demonstrate that it is safe and effective in increasing smokers’ chances of successfully quitting, with the most frequent side-effect being mild nausea (16-42% of users). The nausea is less marked at lower doses, and also appears less when taking the pill along with food and water. Most people using Chantix are able to continue using it and the initial nausea subsides. Those continuing to take Chantix for the full course (up to 24 weeks) tend to have higher quit rates than those discontinuing early.

Labels: addiction, cessation, Chantix, cigarette smoking, nicotine, tobacco, varenicline

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Which nicotine replacement therapy?

Nicotine replacement therapy (NRT) is the name given to FDA-approved medicines containing nicotine that are used to reduce nicotine withdrawal symptoms and cravings and to help smokers quit. Currently there are 5 main types: patch, gum, lozenge, nasal spray and inhaler. These latter two (nasal spray and inhaler) are only available via prescription in the United States, although they are available over-the-counter in many other countries (e.g. UK).

Each type of NRT has its own advantages and disadvantages. The patch is by far the most commonly used NRT, largely because it is the easiest to use, requiring only a single patch application per day. Another advantage of the patch is that its side effects are usually mild – primarily mild skin irritation and itching. The main disadvantage is that there is nothing one can do with the patch to increase the dose when you feel the need for more nicotine.

The gum and the lozenge are broadly similar in terms of dose (each available in 2mg and 4mg formats) and route of administration. The main challenge facing the gum chewer is to adopt a “chew and park” style, such that you chew the gum a few times to release a peppery taste (nicotine) and then park it in the side of your mouth for a few minutes before chewing again. The labeling on the gum suggests that people who smoke less than 25 cigarettes per day should use 2mg (rather than 4mg) and the labeling on the lozenge states that those who don’t smoke within 30 minutes of waking in the morning should use the 2mg lozenge. In practice many clinicians have learned that this labeling (especially the gum) is a recipe for under-dosing and advise all but the lightest smokers to use the 4mg formulation of each product. To get a real benefit from these products you need to use enough. Most users only take 3 or 4 per day in response to cravings. You can get a far greater benefit by taking one per hour (to prevent cravings and withdrawal symptoms) plus another whenever you have a breakthrough craving.

I described the nicotine nasal spray in some detail a few days ago. It appears to be particularly helpful for heavy addicted smokers who are willing to persevere despite the initial nasal irritation. Make sure you have some Kleenex handy when you first try the spray. The initial doses sting and will make you sneeze. But, just as with smoking, you will get used to it within a few days, and within a week will probably like it!

The inhaler‘s main advantage is that it enables the smoker to continue with a similar hand/mouth habit, but it helps to gradually wean them off nicotine. The main thing to note is that one puff on a cigarette delivers a similar amount of nicotine to ten puffs on the inhaler. This means that in order to obtain a therapeutic dose, the ex-smoker has to be puffing on the nicotine inhaler almost all the time. We recommend puffing on the inhaler for 20 minutes out of ever waking hour. Again, people who get into that regular use habit early on tend to do very well with the inhaler.

Some years ago Professor Peter Hajek and colleagues at the University of London conducted a randomized trial comparing the nicotine patch, gum, nasal spray and inhaler. In practice they all had similar quit rates (around 20-25% complete abstinence 3 months later), although women did better on the inhaler than the gum and men were the opposite. Prior to their quit attempt, participants were shown videos describing each NRT and were then allowed to rate their preferences. They were each then randomly allocated to one product. This meant that some people were allocated the product that was their first preference, whereas most were not. However, at the end of the study the smoking cessation outcomes were similar for those receiving their preferred NRT versus those being randomly allocated to a less preferred NRT. Also, people came to prefer the product they were given after they had used it for a week.

One final thing to consider is that the products differ in the risk of inducing dependence. It is extremely rare for someone to have any difficulty coming off the patch (which typically have a built-in reduction plan, involving using smaller sized patches over 4 weeks). However, some people (about 5-10%) find themselves using the gum, inhaler or lozenge long term (i.e. over 3 months and possibly continuing for years). The nicotine nasal spray has the highest dependence potential, with around 10-15% of those who use it continuing use after 3 months. The risk of becoming dependent is related to the speed of nicotine delivery from the product (spray fastest, but still slower and lower dose than a cigarette, whereas the patch delivers nicotine very slowly). It also seems to be related to how addicted the person was to their cigarettes. Thus people who smoked over a pack a day and smoke within 30 minutes of waking in the morning (or wake at night to smoke) are more likely to become a long term user of their NRT product. However, in the placebo-controlled trials these were precisely the people who were much less likely to succeed in quitting if they received the placebo. The thing to remember here is that it is much better to be a long term user of an NRT product delivering only nicotine, than a continuing user of a product that delivers a higher dose of nicotine plus 4000 other toxic chemicals (i.e. a cigarette).

Recently a group of experts in the treatment of tobacco addiction got together to produce a consensus statement guiding consumers on the most effective ways to use NRT to help them quit smoking. You can find a copy of the paper and the summary (in both English and Spanish) at: http://proyectovidanofume.org/publication.htm

Labels: addiction, cigarette, nicotine, NRT, replacement, Smoking, therapy, tobacco

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