Self-titration of nicotine: evidence from the Scottish Heart Health Study

The Relationship Between Reported Daily Nicotine Dose from NRT and Daily Cigarette Consumption in Pregnant Women Who Smoke in an Observational Cohort Study

INTRODUCTION

For nonpregnant people unable to quit smoking, the NHS recommends nicotine replacement therapy (NRT) for smoking reduction. This is not recommended during pregnancy due to concerns about higher nicotine intake than smoking alone. We investigated the relationship between daily nicotine dose from NRT and cigarette consumption reported by pregnant women receiving smoking cessation support.

METHODS

We conducted secondary analysis of data from currently smoking pregnant women, recruited from antenatal clinics (Nottingham University Hospitals, UK) or online between June 2019-September 2020. Participants set a quit date, received a prototype NRT adherence intervention, and reported cigarettes per day (CPD) and daily NRT dose (mg) via smartphone app for 28 days.

RESULTS

388 women were screened, 32 (8%) were eligible and joined the study. 24 (75%) submitted 510 app reports in total. 17 (71%) reported smoking and using NRT concurrently on at least one day, with concurrent use reported on 109 (21%) of app reports.The relationship between daily NRT dose and CPD followed an exponential decay curve of approximately 7%. In multilevel repeated measures modelling using 4 linear splines (knots 17, 40, and 85 mg/NRT), significant fixed effects of daily NRT dose on CPD were observed for splines 1, 3, and 4. The strongest association was spline 1 (0-17 mg/NRT), where each 10 mg NRT increase was associated with a 0.6 CPD reduction (24% on average).

CONCLUSIONS

Among women in a cessation study, many smoked and used NRT concurrently; within these women, daily nicotine dose and heaviness of smoking were inversely related.

IMPLICATIONS

Findings have implications for the design of future interventions intended to reduce harm associated with smoking in pregnancy. They suggest using NRT alongside smoking in pregnancy could help some women reduce the number of cigarettes they smoke per day.

A Low-Cost, High-Throughput Digital Image Analysis of Stain Patterns on Smoked Cigarette Filter Butts to Estimate Mainstream Smoke Exposure

Standard machine smoking protocols provide useful information for examining the impact of design parameters, such as filter ventilation, on mainstream smoke delivery. Unfortunately, their results do not accurately reflect human smoke exposure. Clinical research and topography devices in human studies yield insights into how products are used, but a clinical setting or smoking a cigarette attached to such a device may alter smoking behavior. To better understand smokers' use of filtered cigarette products in a more natural environment, we developed a low-cost, high-throughput approach to estimate mainstream cigarette smoke exposure on a per-cigarette basis. This approach uses an inexpensive flatbed scanner to scan smoked cigarette filter butts and custom software to analyze tar-staining patterns. Total luminosity, or optical staining density, of the scanned images provides quantitative information proportional to mainstream smoke-constituent deliveries on a cigarette-by-cigarette basis. Duplicate sample analysis using this new approach and our laboratory's gold-standard liquid chromatography/tandem mass spectrometry (LC/MS/MS) solanesol method yielded comparable results (+7% bias) from the analysis of 20 commercial cigarettes brands (menthol and nonmentholated). The brands varied in design parameters such as length, filter ventilation, and diameter. Plots correlating the luminosity to mainstream smoked-nicotine deliveries on a per-cigarette basis for these cigarette brands were linear (average R2 > 0.91 for nicotine and R2 > 0.83 for the tobacco-specific nitrosamine NNK), on a per-brand basis, with linearity ranging from 0.15 to 3.00 mg nicotine/cigarette. Analysis of spent cigarette filters allows exposures to be characterized on a per-cigarette basis or a "daily dose" via summing across results from all filter butts collected over a 24 h period. This scanner method has a 100-fold lower initial capital cost for equipment than the LC/MS/MS solanesol method and provides high-throughput results (~200 samples per day). Thus, this new method is useful for characterizing exposure related to filtered tobacco-product use.

Comparison of the chemical composition of aerosols from heated tobacco products, electronic cigarettes and tobacco cigarettes and their toxic impacts on the human bronchial epithelial BEAS-2B cells

The electronic cigarettes (e-cigs) and more recently the heated tobacco products (HTP) provide alternatives for smokers as they are generally perceived to be less harmful than conventional cigarettes. However, it is crucial to compare the health risks of these different emergent devices, in order to determine which product should be preferred to substitute cigarette. The present study aimed to compare the composition of emissions from HTP, e-cigs and conventional cigarettes, regarding selected harmful or potentially harmful compounds, and their toxic impacts on the human bronchial epithelial BEAS-2B cells. The HTP emitted less polycyclic aromatic hydrocarbons and carbonyls than the conventional cigarette. However, amounts of these compounds in HTP aerosols were still higher than in e-cig vapours. Concordantly, HTP aerosol showed reduced cytotoxicity compared to cigarette smoke but higher than e-cig vapours. HTP and e-cig had the potential to increase oxidative stress and inflammatory response, in a manner similar to that of cigarette smoke, but after more intensive exposures. In addition, increasing e-cig power impacted levels of certain toxic compounds and related oxidative stress. This study provides important data necessary for risk assessment by demonstrating that HTP might be less harmful than tobacco cigarette but considerably more harmful than e-cig.

Changes in Puffing Topography and Nicotine Consumption Depending on the Power Setting of Electronic Cigarettes

Introduction

The study purpose was to evaluate changes in puffing topography of experienced electronic cigarette users (vapers) when changing power settings in electronic cigarette battery devices.

Methods

Experienced adult vapers (n = 21) were recruited. Participants used their own liquids and an atomizer and battery provided by the researchers. Two 30-minute sessions were performed, with the device power set at 6 W and 10 W, in a randomized, crossover, participant-blinded design. Puff number and duration (mean [SD]) were recorded in the provided electronic cigarette battery device, whereas the atomizers were weighted before and after use to determine liquid and nicotine consumption.

Results

Puff number and puff duration were lower at 10 W (46 [16] puffs and 3.8 [0.8] s) compared with 6 W (57 [20] puffs and 4.6 [1.0] s). Liquid and nicotine consumption was higher at 10 W (373 [176] mg and 4.2 [2.4] mg, respectively) compared with 6 W (308 [165] mg and 3.5 [2.3] mg, respectively). Vapers reported more aerosol volume and ease of use at 10 W compared with 6 W.

Conclusions

The study identified an attempt for compensatory puffing patterns and nicotine self-titration, with a change in puffing patterns (puff number and duration) observed when changing the power settings of an e-cigarette device.

Implications

Compensatory smoking behavior and nicotine self-titration is a well-established phenomenon. In electronic cigarettes, changing nicotine concentration in the liquid has been shown to trigger a compensatory puffing pattern. Herein, power setting of the electronic cigarette device was found to be a parameter associated with changes in puffing behavior, whereas higher power was preferable for the participants. These findings could contribute to the understanding of patterns of electronic cigarette use and could explain the preference of dedicated vapers to higher power devices. Additionally, laboratory studies evaluating aerosol emissions should consider using different puffing patterns according to the power settings tested.

When Less is More: Vaping Low-Nicotine vs. High-Nicotine E-Liquid is Compensated by Increased Wattage and Higher Liquid Consumption

(1) Background: Previous research (Van Gucht, Adriaens, and Baeyens, 2017) showed that almost all (99%) of the 203 surveyed customers of a Dutch online vape shop had a history of smoking before they had started using an e-cigarette. Almost all were daily vapers who used on average 20 mL e-liquid per week, with an average nicotine concentration of 10 mg/mL. In the current study, we wanted to investigate certain evolutions with regard to technical aspects of vaping behaviour, such as wattage, the volume of e-liquid used and nicotine concentration. In recent years, much more powerful devices have become widely available, e-liquids with very low nicotine concentrations have become the rule rather than the exception in the market supply, and the legislation has been adjusted, including a restriction on maximum nicotine concentrations to 20 mg/mL. (2) Methods: Customers (n = 150) from the same Dutch online vape shop were contacted (to allow a historical comparison), as well as 274 visitors from the Facebook group “Belgian Vape Bond” to compare between groups from two different geographies and/or vaping cultures. (3) Results: Most results were in line with earlier findings: Almost all surveyed vapers were (ex-)smokers, had started (80%) vaping to quit smoking and reported similar positive effects of having switched from smoking to vaping (e.g., improved health). A striking observation, however, was that whereas customers of the Dutch online vape shop used e-liquids with a similar nicotine concentration as that observed previously, the Belgian vapers used e-liquids with a significantly lower nicotine concentration but consumed much more of it. The resulting intake of the total quantity of nicotine did not differ between groups. (4) Conclusions: Among vapers, different vaping typologies may exist, depending on subcultural and/or geographic parameters. As a consequence of choosing low nicotine concentrations and consuming more e-liquid, the Belgian vapers may have a greater potential to expose themselves to larger quantities of harmful or potentially harmful constituents (HPHCs) released during vaping.

Cigarette Filter Ventilation and its Relationship to Increasing Rates of Lung Adenocarcinoma

The 2014 Surgeon General's Report on smoking and health concluded that changing cigarette designs have caused an increase in lung adenocarcinomas, implicating cigarette filter ventilation that lowers smoking machine tar yields. The Food and Drug Administration (FDA) now has the authority to regulate cigarette design if doing so would improve public health. To support a potential regulatory action, two weight-of-evidence reviews were applied for causally relating filter ventilation to lung adenocarcinoma. Published scientific literature (3284 citations) and internal tobacco company documents contributed to causation analysis evidence blocks and the identification of research gaps. Filter ventilation was adopted in the mid-1960s and was initially equated with making a cigarette safer. Since then, lung adenocarcinoma rates paradoxically increased relative to other lung cancer subtypes. Filter ventilation 1) alters tobacco combustion, increasing smoke toxicants; 2) allows for elasticity of use so that smokers inhale more smoke to maintain their nicotine intake; and 3) causes a false perception of lower health risk from "lighter" smoke. Seemingly not supportive of a causal relationship is that human exposure biomarker studies indicate no reduction in exposure, but these do not measure exposure in the lung or utilize known biomarkers of harm. Altered puffing and inhalation may make smoke available to lung cells prone to adenocarcinomas. The analysis strongly suggests that filter ventilation has contributed to the rise in lung adenocarcinomas among smokers. Thus, the FDA should consider regulating its use, up to and including a ban. Herein, we propose a research agenda to support such an effort.

Changes in cigarette smoking initiation, cessation, and relapse among U.S. adults: a comparison of two longitudinal samples

BACKGROUND

The tobacco epidemic in the U.S. has matured in the past decade. However, due to rapidly changing social policy and commercial environments, tailored prevention and interventions are needed to support further reduction in smoking.

METHODS

Using Tobacco Use Supplement to the Current Population Survey (TUS-CPS) 2002-2003 and 2010-2011 longitudinal cohorts, five smoking states are defined including daily-heavy, daily-light, non-daily, former and non-smoker. We quantified the changes between smoking states for the two longitudinal cohorts, and used a series of multivariable logistic regression models to examine the association of socio-demographic attributes and initial smoking states on smoking initiation, cessation, and relapse between waves within each cohort.

RESULTS

The prevalence of adult heavy smoking decreased from 9.9% (95% CI: 9.6%, 10.2%) in 2002 to 7.1% (95% CI: 6.9%, 7.4%) in 2010. Non-daily smokers were less likely to quit in the 2010-2011 cohort than the 2002-2003 cohort (37.0% vs. 44.9%). Gender, age group, smoker type, race and marital status exhibit similar patterns in terms of their association to the odds of initiation, cessation and relapse between the two cohorts, while education groups showed some inconsistent results between the two cohorts regarding the odds of cessation.

CONCLUSIONS

Transitions between smoking states are complex and increasingly unstable, requiring a holistic, population-based perspective to understand the stocks and flows that ultimately dictate the public health impact of cigarette smoking behavior. This knowledge helps to identify groups in need of increased tobacco control prevention and intervention efforts.

Comparative risk assessment of tobacco smoke constituents using the margin of exposure approach: the neglected contribution of nicotine

Nicotine was not included in previous efforts to identify the most important toxicants of tobacco smoke. A health risk assessment of nicotine for smokers of cigarettes was conducted using the margin of exposure (MOE) approach and results were compared to literature MOEs of various other tobacco toxicants. The MOE is defined as ratio between toxicological threshold (benchmark dose) and estimated human intake. Dose-response modelling of human and animal data was used to derive the benchmark dose. The MOE was calculated using probabilistic Monte Carlo simulations for daily cigarette smokers. Benchmark dose values ranged from 0.004 mg/kg bodyweight for symptoms of intoxication in children to 3 mg/kg bodyweight for mortality in animals; MOEs ranged from below 1 up to 7.6 indicating a considerable consumer risk. The dimension of the MOEs is similar to those of other tobacco toxicants with high concerns relating to adverse health effects such as acrolein or formaldehyde. Owing to the lack of toxicological data in particular relating to cancer, long term animal testing studies for nicotine are urgently necessary. There is immediate need of action concerning the risk of nicotine also with regard to electronic cigarettes and smokeless tobacco.

E-cigarette puffing patterns associated with high and low nicotine e-liquid strength: effects on toxicant and carcinogen exposure

BACKGROUND

Contrary to intuition, use of lower strength nicotine e-liquids might not offer reduced health risk if compensatory puffing behaviour occurs. Compensatory puffing (e.g. more frequent, longer puffs) or user behaviour (increasing the wattage) can lead to higher temperatures at which glycerine and propylene glycol (solvents used in e-liquids) undergo decomposition to carbonyl compounds, including the carcinogens formaldehyde and acetaldehyde. This study aims to document puffing patterns and user behaviour associated with using high and low strength nicotine e-liquid and associated toxicant/carcinogen exposure in experienced e-cigarette users (known as vapers herein).

METHODS/DESIGN

A counterbalanced repeated measures design.

PARTICIPANTS

Non-tobacco smoking vapers; have used an e-cigarette for ≥3 months; currently using nicotine strength e-liquid ≥12mg/mL and a second or third generation device.

INTERVENTION

This study will measure puffing patterns in vapers whilst they use high and low strength nicotine e-liquid under fixed and user-defined settings, each for a week. The 4 counterbalanced conditions are: i) low strength (6mg/mL), fixed settings; ii) low strength user-defined settings; iii) high strength (18mg/mL) fixed settings; iv) high strength user-defined settings. Biomarkers of exposure to toxicants and carcinogens will be measured in urine. In the second phase of this study, toxicant yields will be measured in aerosol generated using a smoking machine operated to replicate the puffing behaviours of each participant.

PRIMARY OUTCOMES

i) Puffing patterns (mean puff number, puff duration, inter-puff interval and mL of liquid consumed) and user behaviour (changes to device settings: voltage and air-flow) associated with using high and low strength nicotine e-liquid. ii) Toxicant/carcinogen exposure associated with the puffing patterns/device settings used by our participants.

SECONDARY OUTCOMES

i) Subjective effects. ii) comparisons with toxicant exposure from tobacco smoke (using documented evidence) and with recommended safety limits.

SAMPLE SIZE

Twenty participants.

DISCUSSION

The findings will have important implications for public health messaging regarding the relative risks and subjective effects associated with using high and low strength nicotine e-liquid, and for policy makers regarding regulations on nicotine concentrations in e-liquids.

Self-titration by experienced e-cigarette users: blood nicotine delivery and subjective effects

RATIONALE

Self-titration is well documented in the tobacco literature. The extent to which e-cigarette users (vapers) self-titrate is unknown.

OBJECTIVE

This study explored the effects of high and low nicotine strength liquid on puffing topography, nicotine delivery and subjective effects in experienced vapers.

METHODS

Eleven experienced male vapers completed 60 min of ad libitum vaping under low (6 mg/mL) and high (24 mg/mL) nicotine liquid conditions in two separate sessions. Measurements included puffing topography (puff number, puff duration, volume of liquid consumed) and changes in plasma nicotine levels, craving, withdrawal symptoms, self-reported hit, satisfaction and adverse effects.

RESULTS

Liquid consumption and puff number were higher and puff duration longer, in the low nicotine strength condition (all ps < 0.01). The mean difference in nicotine boost from baseline in the low condition was 8.59 (7.52) ng/mL, 16.99 (11.72) ng/mL and 22.03 (16.19) ng/mL at 10, 30 and 60 min, respectively. Corresponding values for the high condition were 33.77 (34.88) ng/mL, 35.48 (28.31) ng/mL and 43.57 (34.78) ng/mL (ps < 0.05). There were no statistically significant differences between conditions in self-reported craving, withdrawal symptoms, satisfaction, hit or adverse effects.

CONCLUSIONS

Vapers engaged in compensatory puffing with lower nicotine strength liquid, doubling their consumption. Whilst compensatory puffing was sufficient to reduce craving and withdrawal discomfort, self-titration was incomplete with significantly higher plasma nicotine levels in the high condition.

Time to First Cigarette, a Proxy of Nicotine Dependence, Increases the Risk of Pulmonary Impairment, Independently of Current and Lifetime Smoking Behavior

INTRODUCTION

Cigarette smoking is the largest known risk factor for chronic obstructive pulmonary disease (COPD), but little is known about the role of time to first cigarette (TTFC), an indicator of nicotine dependence (ND). This study examines whether daily TTFC is associated with pulmonary outcomes, independently of smoking behavior.

METHODS

A cross-sectional sample of 1461 current adult smokers were drawn from the National Health and Nutrition Examination Survey (NHANES), 2007-2010. The relationships of daily TTFC with outcomes of spirometry-defined pulmonary impairment and self-reported respiratory symptoms (coughing, bringing up phlegm, and wheezing) were examined (1) at the unadjusted level, (2) after adjusting for smoking heaviness and duration, and (3) after also adjusting for environmental exposure and demographics.

RESULTS

In fully-adjusted weighted regressions, those reporting TTFC ≤ 5 minutes were three times as likely to have COPD (confidence interval [CI] = 1.30-8.77), had a 3% lower forced vital capacity expired in the first second (FEV1/FVC) (CI = -0.051 to -0.009), were seven times as likely to report coughing (CI = 1.96-26.41), and 16 times as likely to report bringing up phlegm (CI = 3.43-74.82), relative to those reporting TTFC > 60 minutes. Similar associations were often found when comparing TTFC between 5 to 30 minutes and TTFC between 30 to 60 minutes with TTFC > 60 minutes.

CONCLUSIONS

"Addicted" smoking, as measured by earlier TTFC, is associated with a markedly increased risk of spirometry-measured obstructive pulmonary impairment, and of reporting symptoms of coughing and phlegm, even after controlling for smoking behavior and other risk factors for COPD. TTFC may prove valuable in more precisely assessing smokers' risk of pulmonary impairment.

IMPLICATIONS

This study shows that smoking sooner after waking, a reliable indicator of ND, substantially increases the risk of spirometry-defined pulmonary impairment and self-reported symptoms, independently of lifetime and current smoking behavior. This study adds to a small body of literature examining health outcomes associated with higher ND, including outcomes of COPD. The current study overcomes important shortcomings of these existing studies in at least two ways: controlling for other known risk factors for COPD, and using empirical, spirometry-defined outcomes pulmonary function rather than self-reported COPD outcomes.

Conflation of cocaine seeking and cocaine taking responses in IV self-administration experiments in rats: methodological and interpretational considerations

IV drug self-administration is a special case of an operant task. In most operant experiments, the instrumental response that completes the schedule requirement is separate and distinct from the consumptive response (e.g. eating or drinking) that follows the delivery of the reinforcing stimulus. In most IV self-administration studies drug seeking and drug taking responses are conflated. The instrumental lever press or nose poke is also a consumptive response. The conflation of these two response classes has important implications for interpretation of the data as they are differentially regulated by dose and price. The types of pharmacological pretreatments that affect appetitive responses are not necessarily the same as those that affect consumptive responses suggesting that the neurobiology of the two response classes are to some extent controlled by different mechanisms. This review discusses how schedules of reinforcement and behavioral economic analyses can be used to assess the regulation of drug seeking and drug taking separately. New methods are described that allow the examination of appetitive or consumptive responding in isolation and provide subjects with greater control over the self-administered dose. These procedures provide novel insights into the regulation of drug intake. Cocaine intake patterns that result in large, intermittent spikes in cocaine levels are shown to produce increases in appetitive responding (i.e. drug seeking). The mechanisms that control drug intake should be considered distinct from appetitive and motivational processes and should be taken into consideration in future IV self-administration studies.

Developmental nicotine exposure alters AMPA neurotransmission in the hypoglossal motor nucleus and pre-Botzinger complex of neonatal rats

Developmental nicotine exposure (DNE) impacts central respiratory control in neonates born to smoking mothers. We previously showed that DNE enhances the respiratory motor response to bath application of AMPA to the brainstem, although it was unclear which brainstem respiratory neurons mediated these effects (Pilarski and Fregosi, 2009). Here we examine how DNE influences AMPA-type glutamatergic neurotransmission in the pre-Bötzinger complex (pre-BötC) and the hypoglossal motor nucleus (XIIMN), which are neuronal populations located in the medulla that are necessary for normal breathing. Using rhythmic brainstem slices from neonatal rats, we microinjected AMPA into the pre-BötC or the XIIMN while recording from XII nerve rootlets (XIIn) as an index of respiratory motor output. DNE increased the duration of tonic activity and reduced rhythmic burst amplitude after AMPA microinjection into the XIIMN. Also, DNE led to an increase in respiratory burst frequency after AMPA injection into the pre-BötC. Whole-cell patch-clamp recordings of XII motoneurons showed that DNE increased motoneuron excitability but did not change inward currents. Immunohistochemical studies indicate that DNE reduced the expression of glutamate receptor subunits 2 and 3 (GluR2/3) in the XIIMN and the pre-BötC. Our data show that DNE alters AMPAergic synaptic transmission in both the XIIMN and pre-BötC, although the mechanism by which this occurs is unclear. We suggest that the DNE-induced reduction in GluR2/3 may represent an attempt to compensate for increased cell excitability, consistent with mechanisms underlying homeostatic plasticity.

Characterizing smoking topography of cannabis in heavy users

RATIONALE

Little is known about the smoking topography characteristics of heavy cannabis users. Such measures may be able to predict cannabis use-related outcomes and could be used to validate self-reported measures of cannabis use.

OBJECTIVES

The current study was conducted to measure cannabis smoking topography characteristics during periods of ad libitum use and to correlate topography assessments with measures of self-reported cannabis use, withdrawal and craving during abstinence, and cognitive task performance.

METHODS

Participants (N = 20) completed an inpatient study in which they alternated between periods of ad libitum cannabis use and abstinence. Measures of self-reported cannabis use, smoking topography, craving, withdrawal, and sleep measures were collected.

RESULTS

Participants smoked with greater intensity (e.g., greater volume, longer duration) on initial cigarette puffs with a steady decline on subsequent puffs. Smoking characteristics were significantly correlated with severity of withdrawal, notably sleep quality and architecture, and craving during abstinence, suggesting dose-related effects of cannabis use on these outcomes. Smoking characteristics generally were not significantly associated with cognitive performance. Smoking topography measures were significantly correlated with self-reported measures of cannabis use, indicating validity of these assessments, but topography measures were more sensitive than self-report in predicting cannabis-related outcomes.

CONCLUSIONS

A dose-effect relationship between cannabis consumption and outcomes believed to be clinically important was observed. With additional research, smoking topography assessments may become a useful clinical tool.

Puffing behavior during the smoking of a single cigarette in tobacco-dependent adolescents

INTRODUCTION

Adult and adolescent smokers regulate their nicotine and smoke intake by smoking low-yield cigarettes more intensely than high-yield cigarettes. One likely mechanism of nicotine regulation is altered puffing topography, which has been demonstrated in adult smokers. The purpose of this study was to examine the pattern of puffing behavior during the smoking of a single cigarette in adolescents.

METHODS

Tobacco-dependent adolescents (n = 89) were enrolled in a treatment trial testing the efficacy of nicotine replacement therapy. About 1 week before their quit date, participants smoked ad libitum one of their usual brand of cigarettes during a laboratory session. Smoking topography measures included puff volume, puff duration, puff velocity, and interpuff interval.

RESULTS

Controlling for sex, race, and number of puffs, puff volume and puff duration decreased 12.8% and 24.5%, respectively, from the first 3 to the last 3 puffs. Puff velocity and interpuff interval increased 14.8% and 13.5%, respectively. Puff volume was positively correlated with puff duration and puff velocity, whereas puff duration and puff velocity were negatively correlated. However, none of the topography measures were correlated with smoking history variables.

DISCUSSION

These results suggest that adolescent smokers, like adults, are able to regulate smoke and nicotine intake on a puff-by-puff basis, therefore indicating that this aspect of smoking control is acquired early in the tobacco-dependence process.

Toxicant exposure in cigarette reducers versus light smokers

BACKGROUND

The extent of exposure to tobacco toxicants in smokers who have reduced their cigarette intake compared with smokers who are light smokers is relatively unknown. The goal of this study is to investigate the occurrence of compensatory smoking in reducers compared with light smokers by measuring toxicant exposure.

METHODS

Participants in two smoking reduction intervention studies (N = 64) were selected for comparison with a group of light smokers (N = 62) who smoked the same number of cigarettes as the reducers. A compensatory smoking score was defined (biomarker level for reducer/biomarker level for light smoker) and calculated for urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides (total NNAL), metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-I-(3-pyridyl)-1-butanone, to measure the degree of smoking compensation in reducers when compared with the light smokers.

RESULTS

The mean level of creatinine-adjusted total NNAL for reducers was over twice that of light smokers even when they smoked about the same number of cigarettes per day. The difference of the mean total NNAL concentrations between light smokers and reducers was highly significant (P < 0.0001). Wide variability in total NNAL concentrations was also observed in reducers, with the extent of this variability between light smokers and reducers being significantly different (P = 0.0005). The level of individual reduction was shown to be a consistent predictor of compensatory smoking (r = 0.50; adjusted Ps = 0.002), with greater cigarette reduction associated with more compensation.

CONCLUSIONS

Compensatory smoking limits the harm reduction value of decreased smoking of cigarettes.

Carboxyhemoglobin and thiocyanate as biomarkers of exposure to carbon monoxide and hydrogen cyanide in tobacco smoke

The determination of biomarkers in human body fluids is a useful tool, which allows the quantitative assessment of the exposure to chemicals or complex mixtures of chemicals and of early biological effects as a result of the exposure. Biomarkers require validation before their successful application in human studies. This review describes some general purposes of human biomonitoring and biomarkers including the requirements for validation. Risk assessment and harm reduction of smoking and tobacco products, respectively, is a very suitable field for the application of biomarkers. A brief historical review shows that the application of biomarkers of exposure and effect in human smoking goes back more than 150 years. Two 'classical' biomarkers of exposure to tobacco, namely carboxyhemoglobin (COHb and its equivalent carbon monoxide in exhalate, COex) and thiocyanate (SCN) in body fluids are discussed in terms of sources of exposure, metabolism, disposition kinetics and influencing host factors. Data on COHb/COex and SCN in nonsmokers and smokers as well as the power to discriminate between smokers and nonsmokers are presented. Both biomarkers are significantly correlated with the daily cigarette consumption. Smoking machine-derived yields of the precursors carbon monoxide and hydrogen cyanide were not correlated with COHb/COex and SCN, respectively. It is concluded that, while COHb/COex is a useful biomarker for assessing the smoke inhalation, preferably in controlled studies, the application of SCN in body fluids as a biomarker for smoking is limited, mainly due to the abundance of other sources for SCN.

Changes in nicotine intake and cigarette use over time in two nationally representative cross-sectional samples of smokers

Population surveys have observed decreases in cigarette use over time among smokers. These decreases have probably been influenced by tobacco control measures implemented over the past several decades, but few data exist on whether smokers have also reduced their nicotine intake. The authors examined data from two cross-sectional National Health and Nutrition Examination Surveys (NHANES), conducted in 1988-1994 and 1999-2002. Laboratory, examination, and interview data from current smokers not reporting nicotine intake from other sources were examined. From NHANES III (1988-1994) to NHANES 1999-2002, the average number of cigarettes smoked per day (CPD) fell by nearly 15% (three cigarettes), while the mean serum cotinine level fell by 13% (30 ng/ml). Finer breakdowns of CPD data in each time period suggested that most of the change occurred in the lower (<10 CPD) and higher (>or=20 CPD) smoking categories. These data suggest that CPD may represent a proxy for exposure to nicotine and perhaps other tobacco smoke constituents on the population level, since the decline in serum cotinine levels observed among smokers closely paralleled the decline in self-reported CPD between 1988-1994 and 1999-2002. In addition, these data are inconsistent with the hypothesis that the remaining population of smokers is becoming more dependent on nicotine over time.

Do reductions in the tar and nicotine yields of cigarettes help to explain recent reductions in lung cancer rates in young men and women in the United States?

Between 1985 and 2000, lung cancer rates in U.S. men and women aged 35-54 yr have declined. To investigate whether these declines can adequately be explained by changes in smoking prevalence, consumption, and duration, or if changes in tar and nicotine yields also contributed, two model-fitting approaches were used. Both approaches used individual person National Health Interview Survey data on smoking prevalence, age of starting and time of quitting, and national estimates of consumption per smoker and yields. Both approaches compared observed rates (by sex and age) relative to 1985, with those predicted after successively including various smoking variables into the model, making varying allowance for compensation for reduced yield. Approach A was simpler, based on mean smoking statistics estimated separately for current and former smokers. Approach B used the multistage model and individual smoking histories to estimate risk. Both approaches showed observed declines in risk were (except for men aged 35-39 yr) clearly greater than predicted based only on prevalence, consumption, and duration. Including yield generally improved the fit. At younger ages, models assuming substantial compensation (consistent with evidence from studies relating nicotine yield and intake) fitted well, but at age 50-54 yr in both sexes and age 45-49 yr in women, the decline was better fitted by models assuming little compensation. The conclusions were not sensitive to the precise parameter values assumed in the modeling. Interpretation is not straightforward, but the findings suggest declines in yields have contributed to the recent declines in rates in young U.S. men and women.

Addiction as a Computational Process Gone Awry

Addictive drugs have been hypothesized to access the same neurophysiological mechanisms as natural learning systems. These natural learning systems can be modeled through temporal-difference reinforcement learning (TDRL), which requires a reward-error signal that has been hypothesized to be carried by dopamine. TDRL learns to predict reward by driving that reward-error signal to zero. By adding a noncompensable drug-induced dopamine increase to a TDRL model, a computational model of addiction is constructed that over-selects actions leading to drug receipt. The model provides an explanation for important aspects of the addiction literature and provides a theoretic view-point with which to address other aspects.

Development of a method to assess cigarette smoke intake

Tar and nicotine deliveries of cigarettes measured using current standardized smoking machine protocols provide poor estimates of smoke exposure. The characteristics of human smoking behavior vary considerably and differ from the rigid parameters used with current standardized smoking machine protocols. Current alternatives, including measurement of biomarkers, are invasive, time-dependent, and can be too expensive to be used as mechanisms for carrying out large-scale investigations required to help determine the influence of cigarette design on smoking behaviors. To obtain more reasonable estimates of mainstream smoke exposure, we developed a method to quantitatively measure solanesol, a naturally occurring component in tobacco that is deposited during smoking in the cigarette filter butt. Quantification of solanesol extracted from the filters using liquid chromatography and tandem mass spectrometry is efficient, rapid, and extremely reliable. We found that the amount of solanesol deposited in a cigarette filter is related to the mainstream smoke deliveries of tar and nicotine under a variety of smoking conditions. In addition, the amount of solanesol trapped in the filter remains stable at least 4 weeks after smoking. Measuring solanesol in cigarette filters as an exposure marker provides a noninvasive means to obtain reasonable estimates of mainstream tar and nicotine smoke deliveries under a wide variety of smoking conditions.

A common genetic defect in nicotine metabolism decreases risk for dependence and lowers cigarette consumption

Nicotine is the primary compound present in tobacco that is responsible for establishing and maintaining tobacco dependence; dependent smokers adjust their smoking behavior to maintain peripheral and central nicotine levels. CYP2A6 is the enzyme responsible for the majority of the inactivation of nicotine in humans. This enzyme is also responsible for activating tobacco-related procarcinogens such as the nitrosamines. This paper outlines how genetic variation in the CYP2A6 gene may protect individuals from becoming nicotine-dependent smokers, and if dependent, how impairment of the CYP2A6 gene function decreases the number of cigarettes consumed by smokers (Pianezza M, Sellers EM, Tyndale RF. 1998. A common genetic defect in nicotine metabolism decreases smoking. Nature 393(6687):750). We also discuss recent findings which suggest that mimicking this gene defect by inhibiting CYP2A6 decreases nicotine metabolism and smoking. Further research is needed in order to improve our understanding of how genetic variation in CYP2A6 alters the risk for nicotine dependence and lowers nicotine consumption. This includes a better understanding of how the genetic variants alter nicotine metabolism in vivo in males and females as well as the role of CYP2A6 genetic variation in risk for tobacco-related cancers. In addition we need to gain a better understanding of how manipulating this enzyme could be used therapeutically in prevention and treatment of smoking as well as in exposure reduction.

Cigarette nicotine yields and nicotine intake among Japanese male workers

OBJECTIVES

To analyse brand nicotine yield including "ultra low" brands (that is, cigarettes yielding less-than-or-equal 0.1 mg of nicotine by Federal Trade Commission (FTC) methods) in relation to nicotine intake (urinary nicotine, cotinine and trans-3'-hydroxycotinine) among 246 Japanese male smokers.

DESIGN

Cross sectional study.

SETTING

Two companies in Osaka, Japan.

SUBJECTS

130 Japanese male workers selected randomly during their annual regular health check up and 116 Japanese male volunteers taking part in a smoking cessation programme.

MAIN OUTCOME MEASUREMENTS

Subjects answered a questionnaire about smoking habits. Following the interview, each participant was asked to smoke his own cigarette and, after extinguishing it, to blow expired air into an apparatus for measuring carbon monoxide concentration. Urine was also collected for the assays of nicotine metabolites.

RESULTS

We found wide variation in urinary nicotine metabolite concentrations at any given nicotine yield. Based on one way analysis of variance (ANOVA), the urinary nicotine metabolite concentrations of ultra low yield cigarette smokers were significantly lower compared to smokers of high (p = 0.002) and medium yield cigarettes (p = 0.017). On the other hand, the estimated nicotine intake per ultra low yield cigarette smoked (0.59 mg) was much higher than the 0.1 mg indicated by machine.

CONCLUSIONS

In this study of Japanese male smokers, actual levels of nicotine intake bore little relation to advertised nicotine yield levels. Our study reinforces the need to warn consumers of inappropriate advertisements of nicotine yields, especially low yield brands.

Is compulsory restriction of tar yield of cigarettes a worthwhile public health policy?

BACKGROUND

Although the notion of a "safe cigarette" has proved an illusion, while people continue to smoke, an issue remains of whether compulsory restriction of tar yield is a worthwhile public health policy.

METHODS

The study group was comprised of a random population sample of middle-aged Scottish men and women-3464 smokers of cigarettes with known tar yield at baseline. Tar yields were classified into low (< 10 mg), low/middle (10-14.99 mg), and middle or high (> or = 15 mg), according to standard groupings. Deaths within the study cohort were recorded over a period of 13 years.

RESULTS

Among low, low/middle, and middle or high tar smokers, 55 (10%), 178 (16%), and 276 (16%), respectively, died. In a comparison group of lifetime never-smokers, 178 (6%) died. After adjustment for daily cigarette dose, duration of smoking, age, gender, social class, type A personality, body mass index, urinary potassium, and antioxidant vitamin consumption, hazard ratios (95% confidence intervals) for all-cause mortality comparing low-tar smokers to low/middle-tar smokers and to middle- or high-tar smokers were 1.64 (1.04-2.58) and 1.46 (0.95-2.26), respectively. Corresponding results for cardiovascular disease were 1.48 (0.74-2.96) and 1.35 (0.79-2.60). For lung cancer, after adjusting for known confounding factors, corresponding hazard ratios were 2.82 (0.98-8.15) and 2.30 (0.81-6.49).

CONCLUSIONS

Smoking any type of cigarette is far more risky than abstaining altogether. Although the results obtained comparing tar levels are limited because of lack of repeat measures of smoking during follow-up, potential residual confounding factors, statistical imprecision, and failure to show a dose-response relationship, results do support the hypothesis that persistent smokers will reduce their tobacco-induced health risk if they smoke cigarettes with < 10 mg of tar. However, the data do not permit quantification of the benefits of switching to lower-tar cigarettes. Worldwide legislation to limit tar levels to 10 mg as an absolute maximum is recommended, while recognizing that this must be part of an integrated approach to tobacco control.

Nicotine yield from machine-smoked cigarettes and nicotine intakes in smokers: evidence from a representative population survey

BACKGROUND

The relevance of nicotine yields from machine-smoked cigarettes for quantifying smokers' nicotine intakes and exposure to cigarette toxins has been called into question. However, most studies of the relationship between nicotine yield and nicotine intake have been on relatively small and unrepresentative samples and have included few smokers of "ultra-low" brands (i.e., those yielding around 1 mg of tar and 0.1 mg of nicotine).

METHODS

We examined the relationship between salivary cotinine (a major metabolite of nicotine) concentrations and nicotine yields of machine-smoked cigarettes in a nationally representative sample of 2031 adult smokers of manufactured cigarettes surveyed in the 1998 Health Survey for England. We used standard linear regression techniques to examine associations and two-sided tests of statistical significance.

RESULTS

Cotinine concentrations varied widely between smokers at any level of nominal brand nicotine yield. On average, cotinine levels were slightly lower in smokers of lower nicotine-yielding brands, but these smokers differed in terms of sex, socioeconomic profile, and cigarette consumption. After we controlled for potential confounders, nicotine yield from the brand smoked accounted for only 0.79% of the variation in saliva cotinine concentrations. Nicotine intake per cigarette smoked, as estimated from salivary cotinine level, did not correspond with machine-smoked yields at any level of nicotine yield. Nicotine intake per cigarette was about eight times greater than machine-smoked yields at the lowest deliveries (1.17 mg estimated nicotine intake per cigarette from brands averaging 0.14-mg delivery from machine smoking) and 1.4 times greater for the highest yield cigarettes (1.31-mg estimated nicotine intake per cigarette from brands averaging 0.91 mg from machine smoking).

CONCLUSIONS

Smokers' tendency to regulate nicotine intake vitiates potential health gains from lower tar and nicotine cigarettes. Current approaches to characterizing tar and nicotine yields of cigarettes provide a simplistic guide to smokers' exposure that is misleading to consumers and regulators alike and should be abandoned.

Gender differences in the pharmacology of nicotine addiction

Smoking rates have declined in recent years less rapidly in women than in men. More adolescent girls than boys are currently smoking. Quitting smoking is reported in many studies to be more difficult in women than in men. These observations suggest that there may be gender differences in the nature of nicotine addiction. Gender differences in various pharmacological processes involved in nicotine addiction are reviewed. Women take in less nicotine from smoking per cigarette than men but, because of slower metabolism, nicotine levels in the body for a given number of cigarettes per day are similar in male and female smokers. Women tend to be less sensitive to the discriminative effects of nicotine and tend to regulate nicotine intake less precisely than men. On the other hand, women appear to be more sensitive to the effects of nicotine in reducing negative affect and reducing body weight. There is a strong association between depression and smoking, and this association appears to be stronger in women than in men. Women tend to respond more to environmental cues associated with smoking than do men. Thus, several lines of evidence suggest that nicotine addiction is different in women than in men. Understanding the basis for gender differences may be of utility in individualizing and optimizing smoking cessation therapy.

Examining the relation between usual-brand nicotine yield, blood cotinine concentration and the nicotine- "compensation" hypothesis

Eight data sets relating usual-brand nicotine yield (FTC method or equivalent) to blood cotinine concentration are reviewed with respect to the so-called nicotine-"compensation" hypothesis, i.e., that all smokers achieve a specific level of nicotine in their blood, regardless of the FTC nicotine yield of the cigarette smoked. The data from the studies reviewed here indicate wide variability in blood cotinine concentrations over the range of FTC nicotine yields and that the nicotine-compensation hypothesis is not supported. On average, blood cotinine concentrations are found to be roughly midway between complete compensation (all smokers absorb equal amounts of nicotine regardless of FTC nicotine yield) and the value expected if there was no compensation (i.e., smokers absorb an amount of nicotine exactly equal to the FTC yield). As a result of individual smoking-behavior differences (number of cigarettes smoked, puff volume, puff frequency inhalation volume and depth, etc.), the data indicate that, on average, smokers achieve roughly 50% lower blood cotinine concentrations than predicted by the nicotine-compensation hypothesis.

Comparison of the nicotine pharmacokinetics of Nicoderm (nicotine transdermal system) and half-hourly cigarette smoking

Nicoderm, a nicotine transdermal system (NTS), provides a continuous, transdermal delivery of nicotine and is used as an aid to smoking cessation. In contrast, cigarette smoking yields nicotine concentrations in plasma that rise and fall with each cigarette. The primary objective of this study was to compare nicotine pharmacokinetics after treatment of subjects with either the NTS or controlled smoking. Fourteen healthy adult male smokers, who smoked at least 30 cigarettes per day, were entered into a randomized crossover design trial that compared the NTS, 21 mg/day applied for 24 hours, with half-hourly smoking during the day. Subjects abstained from smoking for 2 days, and were treated for 5 days with either the NTS (daily) or controlled smoking (30 cigarettes at half-hourly intervals on days 1 and 5; ad libitum smoking on days 2-4). Blood samples were obtained frequently on days 1 and 5 for analysis of nicotine and cotinine. Pharmacokinetic comparisons showed that nicotine Cmax, area under the curve (AUC)inf, and Cavg for the NTS were lower than corresponding values for controlled smoking; Cmax and Cavg values were approximately half those of smoking. Cmax and Cavg values for cotinine were similarly lower for the NTS compared to controlled smoking. For both treatments, plasma nicotine concentrations were higher on day 5 compared to day 1. Thus, the NTS provides concentrations of nicotine that are lower than smoking.

Cigarette smoking, tar yields, and non-fatal myocardial infarction: 14,000 cases and 32,000 controls in the United Kingdom. The International Studies of Infarct Survival (ISIS) Collaborators

OBJECTIVES

To assess the effects of cigarette smoking on the incidence of non-fatal myocardial infarction, and to compare tar in different types of manufactured cigarettes.

METHODS

In the early 1990s responses to a postal questionnaire were obtained from 13,926 survivors of myocardial infarction (cases) recently discharged from hospitals in the United Kingdom and 32,389 of their relatives (controls). Blood had been obtained from cases soon after admission for the index myocardial infarction and was also sought from the controls. 4923 cases and 6880 controls were current smokers of manufactured cigarettes with known tar yields. Almost all tar yields were 7-9 or 12-15 mg/cigarette (mean 7.5 mg for low tar (< 10 mg) and 13.3 for medium tar (> or = 10 mg). The cited risk ratios were standardised for age and sex and compared myocardial infarction rates in current cigarette smokers with those in non-smokers who had not smoked cigarettes regularly in the past 10 years.

RESULTS

At ages 30-49 the rates of myocardial infarction in smokers were about five times those in non-smokers (as defined); at ages 50-59 they were three times those in non-smokers, and even at ages 60-79 they were twice as great as in non-smokers (risk ratio 6.3, 4.7, 3.1, 2.5, and 1.9 at 30-39, 40-49, 50-59, 60-69, 70-79 respectively; each 2P < 0.00001). After standardisation for age, sex, and amount smoked, the rate of non-fatal myocardial infarction was 10.4% (SD 5.4) higher in medium tar than in low tar cigarette smokers (2P = 0.06). This percentage was not significantly greater at ages 30-59 (16.6% (7.1)) than at 60-79 (1.0% (8.5)). In both age ranges the difference in risk between cigarette smokers and non-smokers was much larger than the difference between one type of cigarette and another (risk ratio 3.39 and 3.95 at ages 30-59 for smokers of similar numbers of low and of medium tar cigarettes, and risk ratio 2.35 and 2.37 at ages 60-79). Most possible confounding factors that could be tested for were similar in low and medium tar users, with no significant differences in blood lipid or albumin concentrations.

CONCLUSION

The present study indicates that the imminent change of tar yields in the European Union to comply with an upper limit of 12 mg/cigarette will not increase (and may somewhat decrease) the incidence of myocardial infarction, unless they indirectly help perpetuate tobacco use. Even low tar cigarettes still greatly increase rates of myocardial infarction, however, especially among people in their 30s, 40s, and 50s, and far more risk is avoided by not smoking than by changing from one type of cigarette to another.