Cigarette reduction: an intervention for adolescent smokers

Systematic review and meta-analysis investigating nicotine, cotinine and carbon monoxide exposures in people who both smoke and use nicotine replacement therapy

AIMS

To determine effects of concurrent smoking and nicotine replacement therapy (NRT) use on reported heaviness of smoking, nicotine (cotinine) body fluid and exhaled air carbon monoxide (CO) concentrations.

METHODS

Systematic review and meta-analysis of RCTs, which test interventions permitting concurrent NRT use and smoking and comparing, within participants, outcomes when smoking with those when smoking and using NRT concurrently. Measurements included reported number of cigarettes smoked per day (CPD), body fluid cotinine and expired air CO concentrations.

RESULTS

Twenty-nine studies were included in the review. Meta-analysis of nine showed that, compared with when solely smoking, fewer cigarettes were smoked daily when NRT was used (mean difference during concurrent smoking and NRT use, -2.06 CPD [95% CI = -3.06 to -1.07, P < 0.0001]). Meta-analysis of seven studies revealed a non-significant reduction in exhaled CO during concurrent smoking and NRT use (mean difference, -0.58 ppm [95% CI = -2.18 to 1.03, P = 0.48]), but in the three studies that tested NRT used in the lead-up to quitting (i.e. as preloading), a similar reduction in exhaled CO was statistically significant (mean difference, -2.54 ppm CO [95% CI = -4.14 to -0.95, P = 0.002]). Eleven studies reported cotinine concentrations, but meta-analysis was not possible because of data reporting heterogeneity; of these, seven reported lower cotinine concentrations with concurrent NRT use and smoking, four reported no differences, and none reported higher concentrations.

CONCLUSIONS

People who smoke and also use nicotine replacement therapy report smoking less heavily than people who solely smoke. When nicotine replacement therapy is used in the lead-up to quitting (preloading), this reported smoking reduction has been biochemically confirmed. There is no evidence that concurrent smoking and nicotine replacement therapy use result in greater nicotine exposure than solely smoking.

Smoking reduction interventions for smoking cessation

BACKGROUND

The standard way most people are advised to stop smoking is by quitting abruptly on a designated quit day. However, many people who smoke have tried to quit many times and may like to try an alternative method. Reducing smoking behaviour before quitting could be an alternative approach to cessation. However, before this method can be recommended it is important to ensure that abrupt quitting is not more effective than reducing to quit, and to determine whether there are ways to optimise reduction methods to increase the chances of cessation.

OBJECTIVES

To assess the effect of reduction-to-quit interventions on long-term smoking cessation.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group Specialised Register, MEDLINE, Embase and PsycINFO for studies, using the terms: cold turkey, schedul*, cut* down, cut-down, gradual*, abrupt*, fading, reduc*, taper*, controlled smoking and smoking reduction. We also searched trial registries to identify unpublished studies. Date of the most recent search: 29 October 2018.

SELECTION CRITERIA

Randomised controlled trials in which people who smoked were advised to reduce their smoking consumption before quitting smoking altogether in at least one trial arm. This advice could be delivered using self-help materials or behavioural support, and provided alongside smoking cessation pharmacotherapies or not. We excluded trials that did not assess cessation as an outcome, with follow-up of less than six months, where participants spontaneously reduced without being advised to do so, where the goal of reduction was not to quit altogether, or where participants were advised to switch to cigarettes with lower nicotine levels without reducing the amount of cigarettes smoked or the length of time spent smoking. We also excluded trials carried out in pregnant women.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods. Smoking cessation was measured after at least six months, using the most rigorous definition available, on an intention-to-treat basis. We calculated risk ratios (RRs) and 95% confidence intervals (CIs) for smoking cessation for each study, where possible. We grouped eligible studies according to the type of comparison (no smoking cessation treatment, abrupt quitting interventions, and other reduction-to-quit interventions) and carried out meta-analyses where appropriate, using a Mantel-Haenszel random-effects model. We also extracted data on quit attempts, pre-quit smoking reduction, adverse events (AEs), serious adverse events (SAEs) and nicotine withdrawal symptoms, and meta-analysed these where sufficient data were available.

MAIN RESULTS

We identified 51 trials with 22,509 participants. Most recruited adults from the community using media or local advertising. People enrolled in the studies typically smoked an average of 23 cigarettes a day. We judged 18 of the studies to be at high risk of bias, but restricting the analysis only to the five studies at low or to the 28 studies at unclear risk of bias did not significantly alter results.We identified very low-certainty evidence, limited by risk of bias, inconsistency and imprecision, comparing the effect of reduction-to-quit interventions with no treatment on cessation rates (RR 1.74, 95% CI 0.90 to 3.38; I2 = 45%; 6 studies, 1599 participants). However, when comparing reduction-to-quit interventions with abrupt quitting (standard care) we found evidence that neither approach resulted in superior quit rates (RR 1. 01, 95% CI 0.87 to 1.17; I2 = 29%; 22 studies, 9219 participants). We judged this estimate to be of moderate certainty, due to imprecision. Subgroup analysis provided some evidence (P = 0.01, I2 = 77%) that reduction-to-quit interventions may result in more favourable quit rates than abrupt quitting if varenicline is used as a reduction aid. Our analysis comparing reduction using pharmacotherapy with reduction alone found low-certainty evidence, limited by inconsistency and imprecision, that reduction aided by pharmacotherapy resulted in higher quit rates (RR 1. 68, 95% CI 1.09 to 2.58; I2 = 78%; 11 studies, 8636 participants). However, a significant subgroup analysis (P < 0.001, I2 = 80% for subgroup differences) suggests that this may only be true when fast-acting NRT or varenicline are used (both moderate-certainty evidence) and not when nicotine patch, combination NRT or bupropion are used as an aid (all low- or very low-quality evidence). More evidence is likely to change the interpretation of the latter effects.Although there was some evidence from within-study comparisons that behavioural support for reduction to quit resulted in higher quit rates than self-help resources alone, the relative efficacy of various other characteristics of reduction-to-quit interventions investigated through within- and between-study comparisons did not provide any evidence that they enhanced the success of reduction-to-quit interventions. Pre-quit AEs, SAEs and nicotine withdrawal symptoms were measured variably and infrequently across studies. There was some evidence that AEs occurred more frequently in studies that compared reduction using pharmacotherapy versus no pharmacotherapy; however, the AEs reported were mild and usual symptoms associated with NRT use. There was no clear evidence that the number of people reporting SAEs, or changes in withdrawal symptoms, differed between trial arms.

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that neither reduction-to-quit nor abrupt quitting interventions result in superior long-term quit rates when compared with one another. Evidence comparing the efficacy of reduction-to-quit interventions with no treatment was inconclusive and of low certainty. There is also low-certainty evidence to suggest that reduction-to-quit interventions may be more effective when pharmacotherapy is used as an aid, particularly fast-acting NRT or varenicline (moderate-certainty evidence). Evidence for any adverse effects of reduction-to-quit interventions was sparse, but available data suggested no excess of pre-quit SAEs or withdrawal symptoms. We downgraded the evidence across comparisons due to risk of bias, inconsistency and imprecision. Future research should aim to match any additional components of multicomponent reduction-to-quit interventions across study arms, so that the effect of reduction can be isolated. In particular, well-conducted, adequately-powered studies should focus on investigating the most effective features of reduction-to-quit interventions to maximise cessation rates.

Tobacco cessation interventions for young people

BACKGROUND

Most tobacco control programmes for adolescents are based around prevention of uptake, but teenage smoking is still common. It is unclear if interventions that are effective for adults can also help adolescents to quit. This is the update of a Cochrane Review first published in 2006.

OBJECTIVES

To evaluate the effectiveness of strategies that help young people to stop smoking tobacco.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register in June 2017. This includes reports for trials identified in CENTRAL, MEDLINE, Embase and PsyclNFO.

SELECTION CRITERIA

We included individually and cluster-randomized controlled trials recruiting young people, aged under 20 years, who were regular tobacco smokers. We included any interventions for smoking cessation; these could include pharmacotherapy, psycho-social interventions and complex programmes targeting families, schools or communities. We excluded programmes primarily aimed at prevention of uptake. The primary outcome was smoking status after at least six months' follow-up among those who smoked at baseline.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility of candidate trials and extracted data. We evaluated included studies for risk of bias using standard Cochrane methodology and grouped them by intervention type and by the theoretical basis of the intervention. Where meta-analysis was appropriate, we estimated pooled risk ratios using a Mantel-Haenszel fixed-effect method, based on the quit rates at six months' follow-up.

MAIN RESULTS

Forty-one trials involving more than 13,000 young people met our inclusion criteria (26 individually randomized controlled trials and 15 cluster-randomized trials). We judged the majority of studies to be at high or unclear risk of bias in at least one domain. Interventions were varied, with the majority adopting forms of individual or group counselling, with or without additional self-help materials to form complex interventions. Eight studies used primarily computer or messaging interventions, and four small studies used pharmacological interventions (nicotine patch or gum, or bupropion). There was evidence of an intervention effect for group counselling (9 studies, risk ratio (RR) 1.35, 95% confidence interval (CI) 1.03 to 1.77), but not for individual counselling (7 studies, RR 1.07, 95% CI 0.83 to 1.39), mixed delivery methods (8 studies, RR 1.26, 95% CI 0.95 to 1.66) or the computer or messaging interventions (pooled RRs between 0.79 and 1.18, 9 studies in total). There was no clear evidence for the effectiveness of pharmacological interventions, although confidence intervals were wide (nicotine replacement therapy 3 studies, RR 1.11, 95% CI 0.48 to 2.58; bupropion 1 study RR 1.49, 95% CI 0.55 to 4.02). No subgroup precluded the possibility of a clinically important effect. Studies of pharmacotherapies reported some adverse events considered related to study treatment, though most were mild, whereas no adverse events were reported in studies of behavioural interventions. Our certainty in the findings for all comparisons is low or very low, mainly because of the clinical heterogeneity of the interventions, imprecision in the effect size estimates, and issues with risk of bias.

AUTHORS' CONCLUSIONS

There is limited evidence that either behavioural support or smoking cessation medication increases the proportion of young people that stop smoking in the long-term. Findings are most promising for group-based behavioural interventions, but evidence remains limited for all intervention types. There continues to be a need for well-designed, adequately powered, randomized controlled trials of interventions for this population of smokers.

Applying a Social–Ecological Framework to Factors Related to Nicotine Replacement Therapy for Adolescent Smoking Cessation

Objective:

This systematic review synthesizes factors related to nicotine replacement therapy (NRT) use among adolescents seeking to quit smoking, using the social–ecological model as a guiding framework.

Data Source:

Searches of PubMED, ProQuest, EBSCOhost, and ERIC were conducted in July 2016.

Study Inclusion and Exclusion Criteria:

Original studies of cigarette smokers younger than 18 years that discussed NRT were included.

Data Extraction:

Two reviewers individually extracted study purpose, sample, design, and results.

Data Synthesis:

Factors were categorized by social–ecological model level and summarized.

Results:

A total of 103 907 articles were identified during initial search. After narrowing to peer-reviewed articles in English and eliminating reviews and adult-only studies, we reviewed 51 articles. These 51 articles identified factors from studies at each level of the social–ecological model: intrapersonal ( k = 20), interpersonal ( k = 2), organizational ( k = 7), community ( k = 11), and public policy ( k = 14).

Conclusion:

Findings provide insight into the applicability of NRT for adolescent smoking cessation, and factors by social–ecological model level highlight areas for additional research. Future adolescent NRT studies should assess factors at the interpersonal, organizational, and community levels, as well as the interactions between levels.

Interventions to reduce harm from continued tobacco use

BACKGROUND

Although smoking cessation is currently the only guaranteed way to reduce the harm caused by tobacco smoking, a reasonable secondary tobacco control approach may be to try and reduce the harm from continued tobacco use amongst smokers unable or unwilling to quit. Possible approaches to reduce the exposure to toxins from smoking include reducing the amount of tobacco used, and using less toxic products, such as pharmaceutical, nicotine and potential reduced-exposure tobacco products (PREPs), as an alternative to cigarettes.

OBJECTIVES

To assess the effects of interventions intended to reduce the harm to health of continued tobacco use, we considered the following specific questions: do interventions intended to reduce harm have an effect on long-term health status?; do they lead to a reduction in the number of cigarettes smoked?; do they have an effect on smoking abstinence?; do they have an effect on biomarkers of tobacco exposure?; and do they have an effect on biomarkers of damage caused by tobacco?

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group Trials Register (CRS) on the 21st October 2015, using free-text and MeSH terms for harm reduction, smoking reduction and cigarette reduction.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials of interventions to reduce the amount smoked, or to reduce harm from smoking by means other than cessation. We include studies carried out in smokers with no immediate desire to quit all tobacco use. Primary outcomes were change in cigarette consumption, smoking cessation and any markers of damage or benefit to health, measured at least six months from the start of the intervention.

DATA COLLECTION AND ANALYSIS

We assessed study eligibility for inclusion using standard Cochrane methods. We pooled trials with similar interventions and outcomes (> 50% reduction in cigarettes a day (CPD) and long-term smoking abstinence), using fixed-effect models. Where it was not possible to meta-analyse data, we summarized findings narratively.

MAIN RESULTS

Twenty-four trials evaluated interventions to help those who smoke to cut down the amount smoked or to replace their regular cigarettes with PREPs, compared to placebo, brief intervention, or a comparison intervention. None of these trials directly tested whether harm reduction strategies reduced the harms to health caused by smoking. Most trials (14/24) tested nicotine replacement therapy (NRT) as an intervention to assist reduction. In a pooled analysis of eight trials, NRT significantly increased the likelihood of reducing CPD by at least 50% for people using nicotine gum or inhaler or a choice of product compared to placebo (risk ratio (RR) 1.75, 95% confidence interval (CI) 1.44 to 2.13; 3081 participants). Where average changes from baseline were compared for different measures, carbon monoxide (CO) and cotinine generally showed smaller reductions than CPD. Use of NRT versus placebo also significantly increased the likelihood of ultimately quitting smoking (RR 1.87, 95% CI 1.43 to 2.44; 8 trials, 3081 participants; quality of the evidence: low). Two trials comparing NRT and behavioural support to brief advice found a significant effect on reduction, but no significant effect on cessation. We found one trial investigating each of the following harm reduction intervention aids: bupropion, varenicline, electronic cigarettes, snus, plus another of nicotine patches to facilitate temporary abstinence. The evidence for all five intervention types was therefore imprecise, and it is unclear whether or not these aids increase the likelihood of smoking reduction or cessation. Two trials investigating two different types of behavioural advice and instructions on reducing CPD also provided imprecise evidence. Therefore, the evidence base for this comparison is inadequate to support the use of these types of behavioural advice to reduce smoking. Four studies of PREPs (cigarettes with reduced levels of tar, carbon and nicotine, and in one case delivered using an electronically-heated cigarette smoking system) showed some reduction in exposure to some toxicants, but it is unclear whether this would substantially alter the risk of harm. We judged the included studies to be generally at a low or unclear risk of bias; however, there were some ratings of high risk, due to a lack of blinding and the potential for detection bias. Using the GRADE system, we rated the overall quality of the evidence for our cessation outcomes as 'low' or 'very low', due to imprecision and indirectness. A 'low' grade means that further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. A 'very low' grade means we are very uncertain about the estimate.

AUTHORS' CONCLUSIONS

People who do not wish to quit can be helped to cut down the number of cigarettes they smoke and to quit smoking in the long term, using NRT, despite original intentions not to do so. However, we rated the evidence contributing to the cessation outcome for NRT as 'low' by GRADE standards. There is a lack of evidence to support the use of other harm reduction aids to reduce the harm caused by continued tobacco smoking. This could simply be due to the lack of high-quality studies (our confidence in cessation outcomes for these aids is rated 'low' or 'very low' due to imprecision by GRADE standards), meaning that we may have missed a worthwhile effect, or due to a lack of effect on reduction or quit rates. It is therefore important that more high-quality RCTs are conducted, and that these also measure the long-term health effects of treatments.

Tobacco cessation interventions for young people

BACKGROUND

Most tobacco control programmes for adolescents are based around prevention of uptake, but teenage smoking is still common. It is unclear if interventions that are effective for adults can also help adolescents to quit. This is the second update of a Cochrane review first published in 2006.

OBJECTIVES

To evaluate the effectiveness of strategies that help young people to stop smoking tobacco.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register in February 2013. This includes reports for trials identified in the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and PsyclNFO.

SELECTION CRITERIA

We included randomized controlled trials, cluster-randomized controlled trials and other controlled trials recruiting young people, aged less than 20, who were regular tobacco smokers. We included any interventions; these could include pharmacotherapy, psycho-social interventions and complex programmes targeting families, schools or communities. We excluded programmes primarily aimed at prevention of uptake. The primary outcome was smoking status after at least six months follow-up among those who smoked at baseline.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed the eligibility of candidate trials and extracted data. Included studies were evaluated for risk of bias using standard Cochrane methodology. Where meta-analysis was appropriate, we estimated pooled risk ratios using a Mantel-Haenszel fixed-effect method, based on the quit rates at longest follow-up.

MAIN RESULTS

Twenty-eight trials involving approximately 6000 young people met our inclusion criteria (12 cluster-randomized controlled trials, 14 randomized controlled trials and 2 controlled trials). The majority of studies were judged to be at high or unclear risk of bias in at least one domain. Many studies combined components from various theoretical backgrounds to form complex interventions.The majority used some form of motivational enhancement combined with psychological support such as cognitive behavioural therapy (CBT) and some were tailored to stage of change using the transtheoretical model (TTM). Three trials based mainly on TTM interventions achieved moderate long-term success, with a pooled risk ratio (RR) of 1.56 at one year (95% confidence interval (CI) 1.21 to 2.01). The 12 trials that included some form of motivational enhancement gave an estimated RR of 1.60 (95% CI 1.28 to 2.01). None of the 13 individual trials of complex interventions that included cognitive behavioural therapy achieved statistically significant results, and results were not pooled due to clinical heterogeneity. There was a marginally significant effect of pooling six studies of the Not on Tobacco programme (RR of 1.31, 95% CI 1.01 to 1.71), although three of the trials used abstinence for as little as 24 hours at six months as the cessation outcome. A small trial testing nicotine replacement therapy did not detect a statistically significant effect. Two trials of bupropion, one testing two doses and one testing it as an adjunct to NRT, did not detect significant effects. Studies of pharmacotherapies reported some adverse events considered related to study treatment, though most were mild, whereas no adverse events were reported in studies of behavioural interventions.

AUTHORS' CONCLUSIONS

Complex approaches show promise, with some persistence of abstinence (30 days point prevalence abstinence or continuous abstinence at six months), especially those incorporating elements sensitive to stage of change and using motivational enhancement and CBT. Given the episodic nature of adolescent smoking, more data is needed on sustained quitting. There were few trials with evidence about pharmacological interventions (nicotine replacement and bupropion), and none demonstrated effectiveness for adolescent smokers. There is not yet sufficient evidence to recommend widespread implementation of any one model. There continues to be a need for well-designed adequately powered randomized controlled trials of interventions for this population of smokers.

Efficacy and tolerability of pharmacotherapies to aid smoking cessation in adolescents

Adolescent smoking remains a public health problem. Despite concerns regarding adolescent nicotine dependence, few well-designed smoking cessation studies have been conducted with teen smokers. This is particularly true regarding pharmacologic treatments for nicotine dependence. Currently, pharmacologic aids are not recommended for treating adolescent nicotine dependence, as efficacy has not been shown in this population. This review includes studies that have examined the efficacy of pharmacotherapy for smoking abstinence and/or reduction in cigarette consumption among adolescent smokers who want to quit smoking, laboratory-based adolescent studies that have examined the efficacy of these medications in reducing cravings and/or withdrawal symptoms, and/or studies that have assessed the tolerability of medications for smoking cessation in adolescent smokers. It provides information on the pharmacologic action of each medication, the efficacy of each medication for adolescent smoking cessation, the tolerability of each medication based on reported adverse events, and compliance with the medication protocols. Thirteen relevant articles were identified and included in the review. Nicotine patch (NP), nicotine gum, nicotine nasal spray, bupropion, and varenicline have been studied in adolescent smokers. The adverse events reported in the studies on pharmacology for adolescent smoking suggest that the side effect profiles for nicotine replacement therapy, bupropion, and varenicline are similar to those reported in adult studies. There is some evidence of efficacy of NP and bupropion at the end of treatment (efficacy of varenicline has not been assessed), but none of the medications included in this review were efficacious in promoting long-term smoking cessation among adolescent smokers. It is noted that many of the study protocols did not follow the recommended dose or length of pharmacotherapy for adults, rendering it difficult to determine the true efficacy of medication for adolescent smoking cessation. Future efficacy studies are warranted before recommending pharmacotherapy for adolescent smoking cessation.

Pharmacotherapies for adolescent substance use disorders

There is a paucity of research on pharmacotherapies in adolescents with substance use disorders. This paucity is partly because of the fact that most people with substance dependence do not get diagnosed until early adulthood, that is, after 18 years of age. This article reviews pharmacotherapies used for aversion, substitution, anti-craving, and detoxification of alcohol, nicotine, cocaine, and opioids dependence. Adult research is referenced when applicable and generalized to adolescents with caution. Continued evaluation and development of pharmacotherapy for youth in controlled studies are needed to examine medication effectiveness, safety, potential for abuse, compliance, and potential interactions with other medications or substances of abuse.

A method comparison study of timeline followback and ecological momentary assessment of daily cigarette consumption

INTRODUCTION

Uncertainty exists about how best to measure daily cigarette consumption. Two common measures are timeline followback (TLFB), which involves structured, prompted recall, and ecological momentary assessment (EMA), which involves recording consumption, as it occurs, on a handheld electronic device.

METHODS

We evaluated the agreement between TLFB and EMA measures collected for 14 days prior to the target quit date from 236 smokers in a smoking cessation program. We performed a Bland-Altman analysis to assess agreement of TLFB and EMA using a regression-based model that allows for a nonuniform difference between methods and limits of agreement that can vary with the number of cigarettes smoked.

RESULTS

For pairs of measurements taken on the same smoker, TLFB counts were on average 3.2 cigarettes higher than EMA counts; this difference increased for larger numbers of cigarettes. Using a model that allows for variable limits of agreement, the width of the 95% interval ranged from 8.7 to 61.8 cigarettes, with an average of 26.4 cigarettes. Variation between the methods increased substantially for larger cigarette counts, leading to wider limits and poorer agreement for heavy smokers.

DISCUSSION

Throughout the measurement range, the estimated limits of agreement were far wider than the limits of clinical significance, defined a priori to be 20% of the number of cigarettes smoked. We conclude that TLFB and EMA cannot be considered equivalent for the assessment of daily cigarette consumption, especially for heavy smokers.

Smoking Cessation Services in Adolescent Substance Abuse Treatment: Opportunities Missed?

The majority of adolescents receiving substance abuse treatment also use tobacco, yet there are few data regarding the adoption of tobacco use assessment and smoking cessation services by adolescent treatment programs. Using data from a national sample of adolescent-only treatment programs (n = 154), this research measures the adoption of aspects of assessment and treatment from the Public Health Service's (2000) guideline, Treating Tobacco Use and Dependence. When adoption of four intake/assessment practices was measured, adoption appeared high, but only 45% of programs had adopted all four practices. About 43% of programs offered some type of smoking cessation services. However, there was no association between adoption of intake procedures and the odds of availability of smoking cessation services, suggesting a lack of connection between the identification of treatment needs and the availability of services. The lack of smoking cessation services may represent a missed opportunity for early intervention with this population.

Exposure to a tobacco-specific lung carcinogen in adolescent versus adult smokers

BACKGROUND

Previous studies with adult smokers have shown an association between number of cigarettes smoked per day (CPD) and levels of biomarkers of exposure to the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). This study compared carcinogen and nicotine exposure in adolescent and adult smokers across categories of CPD.

METHOD

Baseline smoking history and biomarker data were merged from six studies to make two samples: one of adolescent smokers and one of adult smokers. Metabolites of NNK, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), and its glucuronides (NNAL-Gluc) and total cotinine were quantified in urine.

RESULTS

CPD was stratified into categories of 5 to 10, 11 to 15, and 16 to 20 CPD. Adolescents tended to have lower mean levels of NNAL plus NNAL-Glucs (total NNAL) compared with adults, although differences were not significant overall. Adolescent mean levels of NNAL/CPD were significantly lower than adult levels only in the 11 to 15 CPD category (P = 0.045). However, a significant positive relationship was observed for total NNAL/CPD by age. No significant differences between adolescents and adults were found in mean levels of total cotinine or cotinine/CPD. A subsample of urines from adolescents and adults were analyzed for NNAL-Glucs and NNAL. Adolescents and adults did not significantly differ in the ratio of NNAL-Glucs to NNAL.

CONCLUSIONS

Adolescent uptake of NNK and nicotine tends to be lower although not statistically different from adults. The lack of significant differences may be due to the wide variation in exposure in adolescents. Some adolescent smokers are exposed to lung carcinogens at levels similar to those of adults.

Interventions to reduce harm from continued tobacco use

BACKGROUND

It may be reasonable to try to reduce the harm from continued smoking amongst smokers unable or unwilling to quit. Possible approaches to reduce the exposure to toxins from smoking include reducing the amount of tobacco used, and using less toxic products. The interventions evaluated in controlled trials have predominantly attempted to reduce the number of cigarettes smoked.

OBJECTIVES

To assess the effect of interventions intended to reduce the harm from smoking on the following: biomarkers of damage caused by tobacco, biomarkers of tobacco exposure, number of cigarettes smoked, quitting, and long-term health status.

SEARCH STRATEGY

We searched the Cochrane Tobacco Addiction Group Specialised Register using free text and MeSH terms for harm reduction, smoking reduction and cigarette reduction. The initial search was in March 2006, updated in March 2007.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials of interventions in tobacco users to reduce amount smoked, or to reduce harm from smoking by means other than cessation. Outcomes were change in cigarette consumption, markers of cigarette exposure and any markers of damage or benefit to health, measured at least six months from the start of the intervention.

DATA COLLECTION AND ANALYSIS

We pooled trials with similar interventions and outcomes using a fixed-effect model. Other studies were summarised narratively.

MAIN RESULTS

The 13 included trials all evaluated interventions to help smokers cut down the amount smoked. Self-reported reduction in cigarettes per day (CPD) was validated by reduction in carbon monoxide (CO) levels. Most trials tested nicotine replacement therapy (NRT) to assist reduction. No eligible studies evaluated the use of potentially reduced-exposure products. In a pooled analysis of eight trials, NRT significantly increased the odds of reducing CPD by 50% or more for people using nicotine gum or inhaler or a choice of product compared to placebo (n=3273, odds ratio [OR] 2.02, 95% confidence interval [CI] 1.55 to 2.62). Where average changes from baseline were compared for different measures, CO and cotinine consistently showed smaller reductions than CPD. Whilst the effect for NRT was significant, small numbers of people in either treatment or control group successfully sustained a reduction of 50% or more. Use of NRT also significantly increased the odds of quitting (OR 1.90, 95% CI 1.46 to 2.47). One trial of bupropion failed to detect an effect on reduction or cessation. Four trials of different types of advice and instructions on reducing CPD did not provide clear evidence.

AUTHORS' CONCLUSIONS

There is insufficient evidence about long-term benefit to give firm support the use of interventions intended to help smokers reduce but not quit tobacco use. Some people who do not wish to quit can be helped to cut down the number of cigarettes smoked and reduce their carbon monoxide levels by using nicotine gum or nicotine inhaler. Because the long-term health benefit of a reduction in smoking rate is unclear this application of NRT is more appropriately used as a precursor to quitting.

Tobacco cessation interventions for young people

BACKGROUND

Teenage smoking prevalence is around 15% in developing countries (with wide variation from country to country), and around 26% in the UK and USA. Although most tobacco control programmes for adolescents are based around prevention of uptake, there are also a number of initiatives to help those who want to quit. Since those who do not smoke before the age of 20 are significantly less likely to start as adults, there is a strong case for programmes for young people that address both prevention and treatment.

OBJECTIVES

To evaluate the effectiveness of strategies that help young people to stop smoking tobacco.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) and the Cochrane Tobacco Addiction Group's Specialized Register, MEDLINE, EMBASE, PsyclNFO, ERIC, CINAHL, and the bibliographies of identified trials. We also searched the 'grey' literature (unpublished materials), and contacted authors and experts in the field where necessary.

SELECTION CRITERIA

Types of studies: Randomized controlled trials, cluster-randomized controlled trials and controlled trials.

TYPES OF PARTICIPANTS

Young people, aged less than 20, who are regular tobacco smokers. Types of interventions: The interventions ranged from simple ones such as pharmacotherapy, targeting individual young people, through complex programmes targeting people or organizations associated with young people (for example, their families or schools), or the community in which young people live. We included cessation programmes but excluded programmes primarily aimed at prevention of uptake. Types of outcome measures: The primary outcome was smoking status at six months follow up, among those who smoked at baseline. We report the definition of cessation used in each trial (e.g seven- or thirty-day point prevalence abstinence, or sustained or prolonged abstinence), and we preferred biochemically verified cessation when that measure was available.

DATA COLLECTION AND ANALYSIS

Both authors independently assessed the eligibility of candidate trials identified by the searches, and extracted data from them. We categorized included trials as being at low, medium or high risk of bias, based on concealment of allocation, blinding (where applicable) and the handling of attrition and losses to follow up. We conducted limited meta-analyses of some of the trials, provided that it was appropriate to group them and provided that there was minimal heterogeneity between them. We estimated pooled odds ratios using the Mantel-Haenszel method, based on the quit rates at longest follow up for trials with at least six months follow up from the start of the intervention.

MAIN RESULTS

We found 15 trials, covering 3605 young people, which met our inclusion criteria (seven cluster-randomized controlled trials, six randomized controlled trials and two controlled trials). Three trials used or tested the transtheoretical model (stages of change) approach, two tested pharmacological aids to quitting (nicotine replacement and bupropion), and the remaining trials used various psycho-social interventions, such as motivational enhancement or behavioural management. The trials evaluating TTM interventions achieved moderate long-term success, with a pooled odds ratio (OR) at one year of 1.70 ( 95% confidence interval (CI) 1.25 to 2.33) persisting at two-year follow up with an OR of 1.38 (95% CI 0.99 to 1.92). Neither of the pharmacological intervention trials achieved statistically significant results (data not pooled), but both were small-scale, with low power to detect an effect. The three interventions (5 trials) which used cognitive behavioural therapy interventions did not individually achieve statistically significant results, although when the three Not on Tobacco trials were pooled the OR 1.87; (95% CI 1.00 to 3.50) suggested some measure of effectiveness. Although the three trials that incorporated motivational interviewing as a component of the intervention achieved a pooled OR of 2.05 (95% CI 1.10 to 3.80), the impossibility of isolating the effect of the motivational interviewing in these trials meant that we could not draw meaningful inferences from that analysis.

AUTHORS' CONCLUSIONS

Complex approaches show promise, with some persistence of abstinence (30 days point prevalence abstinence at six months), especially those incorporating elements sensitive to stage of change. There were few trials with evidence about pharmacological interventions (nicotine replacement and bupropion), and none demonstrated effectiveness for adolescent smokers. Psycho-social interventions have not so far demonstrated effectiveness, although pooled results for the Not on Tobacco trials suggest that that this approach may yet prove to be effective; however, their definition of cessation (one or more smoke-free days) may not adequately account for the episodic nature of much adolescent smoking. There is a need for well-designed adequately powered randomized controlled trials for this population of smokers, with a minimum of six months follow up and rigorous definitions of cessation (sustained and biochemically verified). Attrition and losses to follow up are particularly problematic in trials for young smokers, and need to be kept to a minimum, so that management and interpretation of missing data need not compromise the findings.