Time to First Cigarette and 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanol (NNAL) Levels in Adult Smokers; National Health and Nutrition Examination Survey (NHANES), 2007–2010

Smoking, Lung Cancer Stage, and Prognostic Factors-Findings from the National Lung Screening Trial

BACKGROUND

Low-dose computed tomography (LDCT) increases the early detection of lung cancer. Identifying modifiable behaviors that may affect tumor progression in LDCT-detected patients increases the likelihood of long-term survival and a good quality of life.

METHODS

We examined cigarette smoking behaviors on lung cancer stage, progression, and survival in 299 ever-smoking patients with low-dose CT-detected tumors from the National Lung Screening Trial. Univariate and multivariate Cox models were used to estimate the hazard ratio (HR) for smoking variables on survival time.

RESULTS

Current vs. former smokers and early morning smokers (≤5 min after waking, i.e., time to first cigarette (TTFC) ≤ 5 min) had more advanced-stage lung cancer. The adjusted HR for current vs. former smokers was 1.3 (95% confidence interval [CI] 0.911-1.98, p = 0.136) for overall survival (OS) and 1.3 (0.893-1.87, p = 0.1736) for progression-free survival (PFS). The univariate hazard ratios for TTFC ≤ 5 min vs. >5 min were 1.56 (1.1-2.2, p = 0.013) for OS and 1.53 (1.1-2.12, p = 0.01) for PFS. Among current smokers, the corresponding HRs for early TTFC were 1.78 (1.16-2.74, p = 0.0088) and 1.95 (1.29-2.95, p = 0.0016) for OS and PFS, respectively. In causal mediation analysis, the TTFC effect on survival time was mediated entirely through lung cancer stage.

CONCLUSION

The current findings indicate smoking behaviors at diagnosis may affect lung cancer stage and prognosis.

'Time to first tobacco cigarette soon after waking' occurs more often among underage newly incident smokers in the United States, 2004-2017

AIMS

Time to first cigarette (TTFC) after waking is a highly regarded and readily measured manifestation of a tobacco dependence process. We aim to estimate short TTFC as it occurs very soon after the onset of cigarette smoking (CS) in a community sample of newly incident smokers, all 12-21 years of age, and to study risk variation with the age of CS onset.

METHODS

United States National Surveys on Drug Use and Health, 2004-2017, drew large nationally representative samples of 12-to-21-year-old community residents, and used computerized self-interviews to measure tobacco cigarette smoking, the Fagerstrom TTFC construct, and related variables. A 'short' TTFC was defined as smoking the first cigarette after waking up within 30 min vs. 'long' TTFC or smoking more than 30 min. We studied 8188 newly incident smokers, all assessed within six months after the first puff. Estimated age-specific cumulative incidence proportions (CIP) and odds ratios (OR) are estimated and compared, with due attention to complex survey design and weights.

RESULTS

Among underage newly incident smokers (12-17 years old), an estimated 5.2% experienced short TTFC within 6 months after CS onset (95% CI = 4.4%, 6.2%), versus 3.7% for older new smokers (18-21 years; 95% CI = 2.8%, 4.6%). Underage smokers are 1.5 times more likely to develop short TTFC compared to older initiates (95% CI = 1.1, 2.1). No male-female variations are seen, but exploratory analysis disclosed findings that involve Census-defined race-ethnicity subgroups. Non-Hispanic African-American initiates are twice as likely to develop short TTFC, and Hispanic initiates are less likely to develop short TTFC, as compared with non-Hispanic White smokers.

CONCLUSIONS

Based on US community samples our study offers new evidence about TTFC formation observed within six months after the first puff when cigarette smoking starts before age 18 years.

Time to first cigarette of the day and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in adult regular and non-daily smokers: (NHANES) 2007-10

As the number of regular smokers has decreased over the last decade, the prevalence of light (<10 cigarettes per day) and non-daily smokers has increased. As the FDA continues to develop regulations for tobacco products, understanding factors related to toxin exposure in all smokers is essential. The present study evaluated the relation between the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), as measured by its metabolite, and patterns of heavy smoking (>10 cigarettes per day), light smoking and non-daily smoking and the time to the first cigarette of the day (TTFC), a robust predictor of nicotine addiction, cessation failure, sleep disruption and other health indicators. Findings from a sample of 352 smokers suggest that among intermittent, non-daily and light daily smokers, TTFC of the day was associated with higher levels of NNK metabolite, an effect which was mediated by urinary cotinine levels, but not by the number of cigarettes smoked per day. This suggests these groups of smokers may be puffing each cigarette more intensely, thus increasing nicotine and toxin exposure, despite fewer overall cigarettes. These findings provide further information regarding toxicant exposure associated with lower-frequency smoking and has implications for future regulatory research approaches with lowered nicotine cigarettes and other tobacco products.

A mixed-effects location scale model for time-to-event data: A smoking behavior application

In general, mixed-effects location scale models (MELS) allow assessment of within-person and between-person variability with time-to-event data for outcomes that follow a normal or ordinal distribution. In this article, we extend the mixed-effects location scale model to time-to-event data in relation to smoking data. Better understanding of the time-graded within-person variability of factors involved in nicotine dependence can be helpful to researchers in their efforts to fine-tune smoking cessation programs. We illustrate the MELS model with data on time to first cigarette measured every day for 7 days in smokers randomized to two groups: a) those asked to keep smoking, or b) those asked to stop. Our results show that some individuals remain very stable in their time to first cigarette over the week, while others show variable patterns. The stable individuals smoked every day, did not smoke immediately upon waking, and were all in the group asked to keep smoking. Conversely, the variable individuals had at least one day during which they did not smoke, other days during which they smoked within the first 5 min of waking, and they were almost all in the group asked to quit smoking. These findings suggested that MELS have the potential to provide insights on how people try to stop smoking. More importantly, this model can be applied to other clinically important outcomes such as time to relapse in a range of cessation programs.

Black Light Smokers: How Nicotine Intake and Carcinogen Exposure Differ Across Various Biobehavioral Factors

OBJECTIVE

The study objective was to identify biobehavioral variables associated with greater intake of nicotine and a tobacco carcinogen among Black light smokers who smoke 1 to 10 cigarettes per day (CPD).

METHODS

We analyzed baseline data collected from 426 Black light smokers enrolled in Kick It at Swope III (KIS III), a smoking cessation trial for Black smokers. We examined differences in concentrations of tobacco biomarkers, including urinary total nicotine equivalents (TNE) and total 4-(methylnitrosamino)-1-(3)pyridyl-1-butanonol (NNAL; a human carcinogen), across gender, age, plasma nicotine metabolite ratio (NMR), CPD, and measures of tobacco dependence, including time to first cigarette (TFC), using ANOVA.

RESULTS

Tobacco biomarker levels were significantly higher among those who smoked more CPD (6-10 vs 1-5 CPD) and those with greater reported physical dependence on tobacco. Concurrently, those who smoked 1-5 CPD smoked each cigarette more intensely than those who smoked 6-10 CPD. While we found no gender differences overall, among those who smoked 1-5 CPD, women had higher NNAL levels compared to men. The rate of nicotine metabolism, measured by the nicotine metabolite ratio, was not significantly related to TNE or NNAL levels.

CONCLUSION

Among Black Light smokers, higher cigarette consumption and greater physical dependence-but not rate of nicotine metabolism, menthol use, or socioeconomic status-were associated with greater toxicant exposure and thus a likely increased risk of tobacco-related diseases. The lack of data on light smokers, and specifically on Blacks, make this observation important given the disproportionate burden of lung cancer in this population.

Time to First Cigarette and Self-Reported Health Among US Adult Smokers

Background:

Numerous studies have reported that shorter time to first cigarette (TTFC) is linked to elevated risk for smoking-related morbidity. However, little is known about the influence of early TTFC on self-reported health among current smokers. Hence, the objective of this study was to examine the association between TTFC and self-reported health among US adult smokers.

Methods:

Data came from the 2012-2013 National Adult Tobacco Survey (NATS). Current smokers aged 18 years and older (N = 3323) were categorized into 2 groups based on TTFC: ≤ 5 minutes (n = 1066) and >5 minutes (n = 2257). Propensity score matching (PSM) was used to control selection bias.

Results:

After adjusting for sociodemographic and smoking behavior factors, current smokers with early TTFC had higher odds for poor health in comparison with current smokers with late TTFC in the prematching (adjusted odds ratio [AOR] = 1.65; 95% confidence interval [CI] = 1.31-2.08) and postmatching (AOR = 1.60; 95% CI = 1.22-2.09) samples.

Conclusions:

In conclusion, smokers with early TTFC were associated with increased risk of poor health in the United States. To reduce early TTFC, elaborate efforts are needed to educate people about harms of early TTFC and benefits of stopping early TTFC.

Nicotine dependence as an independent risk factor for atherosclerosis in the National Lung Screening Trial

Background

Atherosclerosis and COPD are systemic inflammatory diseases that share common risk factors including cigarette smoking. A high level of nicotine dependence is emerging as a recently identified risk factor for pulmonary impairment, chronic obstructive pulmonary disease and tobacco-related cancers. We hypothesized that nicotine dependence is associated with the risk of atherosclerosis in long-term cigarette smokers.

Methods

A nested case-control study was conducted within the National Lung Cancer Screening Trial- American College of Radiology Imaging Network. Cases were defined as having a new diagnosis of any type of atherosclerosis. Controls were matched on a 2:1 basis by age, sex, race, study center, smoking status, years of smoking, and frequency of smoking. Dependence was measured by the time to first cigarette after awakening (TTFC).

Results

The study included 166 cases and 286 controls. Compared to participants who smoked within 5 min after waking, the risk of atherosclerosis for participants who smoked an hour or more after waking was borderline non-significant (odds ratio = 0.49, 95% confidence intervals [CI] 0.23, 1.00). Findings were similar for men and women. For aortic atherosclerosis, the corresponding odds ratio was 0.24 (95% CI 0.08, 0.69). Hypertension was associated with an increased risk and body mass index was associated with a decreased risk of aortic atherosclerosis. The TTFC was unrelated to coronary atherosclerosis.

Conclusions

Compared to smoking immediately after waking, delaying an hour or more reduces the risk of aortic atherosclerosis even among long-term heavy smokers. Possible mechanisms that explain this association are intensity of smoking, inflammation and oxidative stress, and elevated lipid levels.

Tobacco Dependence Predicts Higher Lung Cancer and Mortality Rates and Lower Rates of Smoking Cessation in the National Lung Screening Trial

BACKGROUND

Incorporating tobacco treatment within lung cancer screening programs has the potential to influence cessation in high-risk smokers. We aimed to better understand the characteristics of smokers within a screening cohort, correlate those variables with downstream outcomes, and identify predictors of continued smoking.

METHODS

This study is a secondary analysis of the National Lung Screening Trial randomized clinical study. Tobacco dependence was evaluated by using the Fagerstrӧm Test for Nicotine Dependence, the Heaviness of Smoking Index, and time to first cigarette (TTFC); descriptive statistics were performed. Clinical outcomes (smoking cessation, lung cancer, and mortality) were assessed with descriptive statistics and χ² tests stratified according to nicotine dependence. Logistic and Cox regression models were used to study the influence of dependence on smoking cessation and mortality, respectively.

RESULTS

Patients with high dependence scores were less likely to quit smoking compared with low dependence smokers (TTFC OR, 0.50 [95% CI, 0.42-0.60]). Indicators of high dependence, as measured according to all three metrics, were associated with worsening clinical outcomes. TTFC showed that patients who smoked within 5 min of waking (indicating higher dependence) had higher rates of lung cancer (2.07% for > 60 min after waking vs 5.92% ≤ 5 min after waking; hazard ratio [HR], 2.56 [95% CI, 1.49-4.41]), all-cause mortality (5.38% for > 60 min vs 11.21% ≤ 5 min; HR, 2.19 [95% CI, 1.55-3.09]), and lung cancer-specific mortality (0.55% for > 60 min vs 2.92% for ≤ 5 min; HR, 4.46 [95% CI, 1.63-12.21]).

CONCLUSIONS

Using TTFC, a one-question assessment of tobacco dependence, at the time of lung cancer screening has implications for personalizing tobacco treatment and improving risk assessment.

Sex/Gender Differences in Cotinine Levels Among Daily Smokers in the Pennsylvania Adult Smoking Study

BACKGROUND

This study was conducted to determine sex/gender differences in smoke exposure and to quantify the role of potential predictors including puffing behaviors, nicotine dependence, and non-nicotinic factors.

METHODS

The Pennsylvania Adult Smoking Study (PASS) of 332 adult cigarette smokers utilized portable handheld topography devices to capture the smokers' profiles in a naturalistic environment. Sex/gender differences in salivary biomarkers were modeled using ANCOVA to account for measures of dependence (Fagerstrom Test for Nicotine Dependence, nicotine metabolite ratio [3-hydroxycotinine/cotinine]), and nondependence covariates including anthropomorphic factors and stress. The Blinder-Oaxaca method was used to decompose the sex/gender differences in nicotine uptake due to covariates.

RESULTS

Men had significantly higher cotinine levels (313.5 ng/mL vs. 255.8 ng/mL, p < 0.01), cotinine +3-hydroxycotinine levels, (0.0787 mol/L vs. 0.0675 mol/L, p = 0.01), puff volumes (52.95 mL vs. 44.77 mL, p < 0.01), and a lower nicotine metabolite ratio (0.396 vs. 0.475, p = 0.01) than women. The mean Fagerström Test for Nicotine Dependence score did not differ between men and women (p = 0.24). Women had a higher mean Hooked on Tobacco Checklist score than men (7.64 vs. 6.87, p < 0.01). In multivariate analysis, nicotine metabolite levels were not significantly different by sex. Decomposition results show that ten predictors can explain 83% of the sex/gender differences in cotinine uptake. Height was the greatest contributor to these differences, followed by average puff volume. Conclusion and Impact: The higher levels of nicotine metabolites in men, compared to women, can be explained by height, weight, puff volume, and nicotine metabolism.

Potential Impact of Including Time to First Cigarette in Risk Models for Selecting Ever-Smokers for Lung Cancer Screening

INTRODUCTION

Selecting individuals on the basis of model-predicted risks has been reported to improve lung cancer screening efficiency. On the basis of case-control studies, time to first cigarette (TTFC), a nicotine dependency measurement, has been a strong independent predictor of lung cancer risk. Our objective was to verify the TTFC-lung cancer association in the prospective National Lung Screening Trial and evaluate whether adding TTFC can improve lung cancer risk-prediction models.

METHODS

Using Cox models, we examined associations between TTFC (≤5, 6-14, 15-29, 30-59, and ≥60 minutes) and lung cancer incidence and death in 18,729 National Lung Screening Trial participants, adjusting for smoking and other lung cancer risk factors comprehensively. We estimated 5-year individual lung cancer incidence by using models without and with TTFC and dichotomized into screening or no-screening groups based on risk thresholds of 1% and 2%. Area under the receiver operating curve values were calculated for models without and with TTFC.

RESULTS

Smokers with a TTFC of 60 minutes or more had a much lower standardized 5-year lung cancer incidence risk-1.54% (1.52%-1.56%) for TTFC 60 minutes or more versus 4.07% (4.04%-4.09%) for TTFC 5 minutes or less-and lung cancer death risk-0.59% (0.57%-0.61%) for TTFC 60 minutes or more versus 2.26% (2.23%-2.28%) for TTFC 5 minutes or less (p trend < 0.001). Adding TTFC to the lung cancer incidence model improved the area under the receiver operating curve by 0.0079 (95% confidence interval = 0.0019-0.0138 [p = 0.0085]). Among 8994 smokers without a lung cancer diagnosis, 180 (2.00%) and 155 (1.67%) more people would be assigned to the no-screening group by adding TTFC to the model (p values for percent changes <0.001) at the 1% and 2% risk thresholds, respectively.

CONCLUSION

Including TTFC, which can be elicited by a single question at very low cost and noninvasively question, into risk models might better identify smokers with lower risk and could therefore be a safe, convenient tool to improve identification of those who benefit less from lung cancer screening.

Adolescent Rats Self-Administer Less Nicotine Than Adults at Low Doses

INTRODUCTION

Although nearly 90% of current smokers initiated tobacco use during adolescence, little is known about reinforcement by nicotine in adolescents. Researchers are currently investigating whether a potential public health policy setting a tobacco product standard with very low nicotine levels would improve public health, and it is essential to understand whether data generated in adults translates to adolescents, particularly as it relates to the threshold dose of nicotine required to support smoking. The present study compared self-administration of low doses of nicotine between adolescent and adult rats.

METHODS

Adolescent (postnatal day [P] 30) and adult (P90) male and female rats were allowed to nosepoke to receive intravenous infusions of nicotine (3-100 μg/kg/infusion) during 16 daily 1-hour sessions.

RESULTS

At 10 μg/kg/infusion nicotine, adolescent rats earned significantly fewer infusions than adults. When responding for 30 μg/kg/infusion nicotine, rats of both ages earned a similar number of infusions; however, there were subtle differences in the distribution of infusions across the 1-hour session. No sex differences were apparent in either age group at any dose.

CONCLUSIONS

These results demonstrate that adolescent rats are less sensitive than adults to the primary reinforcing effects of nicotine. However, at nicotine doses that support self-administration in both age groups, adolescent and adult rats do not differ in acquisition or number of infusions earned. These results suggest that reducing nicotine levels in cigarettes to a level that does not support smoking in adults may be sufficient to reduce the acquisition of smoking in adolescents.

IMPLICATIONS

The results of the present studies demonstrate that adolescent rats are less sensitive than adults to the primary reinforcing effects of nicotine. These results suggest that reducing nicotine levels in cigarettes to a level that does not support smoking in adults will be sufficient to reduce the acquisition of smoking in adolescents.

Time to First Morning Cigarette and Risk of Chronic Obstructive Pulmonary Disease: Smokers in the PLCO Cancer Screening Trial

BACKGROUND

Time to first cigarette (TTFC) after waking is an indicator of nicotine dependence. The association between TTFC and chronic obstructive pulmonary disease (COPD), the third leading cause of death in the United States, has not yet been reported.

METHODS

We investigated the cross-sectional association between TTFC and prevalent COPD among 6,108 current smokers in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. COPD was defined as a self-reported diagnosis of emphysema, chronic bronchitis, or both. Current smokers in PLCO reported TTFC, the amount of time they typically waited before smoking their first cigarette of the day after waking, in four categories: ≤ 5, 6-30, 31-60, or > 60 minutes. We used logistic regression models to investigate the association between TTFC and prevalent COPD with adjustments for age, gender, race, education, and smoking (cigarettes/day, years smoked during lifetime, pack-years, age at smoking initiation), and prior lung cancer diagnosis.

RESULTS

COPD was reported by 19% of these 6,108 smokers. Individuals with the shortest TTFC had the greatest risk of COPD; compared to those with the longest TTFC (> 60 minutes) the adjusted odds ratios (OR) and 95% confidence intervals (CI) for COPD were 1.48 (95% CI, 1.15-1.91), 1.64 (95% CI, 1.29-2.08), 2.18 (95% CI, 1.65-2.87) for those with TTFC 31-60 minutes, 6-30 minutes, and ≤ 5 minutes, respectively (P-trend < 0.0001). The association between TTFC and emphysema was similar to that for bronchitis, albeit the ORs were slightly stronger for chronic bronchitis; comparing TTFC ≤5 minutes to > 60 minutes, the adjusted OR (95% CI) was 2.29 (1.69-3.12) for emphysema and 2.99 (1.95-4.59) for chronic bronchitis.

CONCLUSIONS

Current smokers with shorter TTFC have increased risk of COPD compared to those with longer TTFC, even after comprehensive adjustment for established smoking covariates. Future epidemiologic studies, including prospective designs, should incorporate TTFC to better assess disease risk and evaluate the potential utility of TTFC as a COPD screening tool for smokers in the clinical setting.

Time to First Use Among Daily Smokers and Smokeless Tobacco Users

INTRODUCTION

Time to the first cigarette after waking up in the morning is the most validated measure of dependence among smokers, and its complement is also a good indicator of dependence for smokeless tobacco (ST) users. However, no studies have directly compared these measures.

METHODS

We used a multivariate logistic regression model to compare the time to first use (TTFU) of cigarettes and ST among white men 18+ years of age who were daily users in the 2003 Tobacco Use Supplement of the Current Population Survey. Smokers were classified as light (1-14 cigarettes per day [cpd]), moderate (15-24 cpd), and heavy (25+ cpd) and ST users were classified as former smokers or exclusive users.

RESULTS

There was no difference in TTFU within 5min between light smokers and exclusive ST users (Odds ratio [OR] = 1.3, CI = 0.95-1.7), but the latter were less likely to use tobacco within 30min (OR = 0.75, CI = 0.62-0.89). ST former smokers were more likely than light smokers to have a TTFU within 5min (OR = 1.5, CI = 1.1-2.0) but not within 30min. Moderate and heavy smokers had significantly higher odds of TTFU within both time points than light smokers.

CONCLUSION

Compared to light smokers, the likelihood of TTFU within 5min was similar among exclusive ST users and was slightly higher among ST former smokers, offering some support for the Fagerström-Eissenberg hypothesis that the dependence level of cigarettes is higher than that of ST.

Time to smoke first morning cigarette and lung cancer in a case-control study

BACKGROUND

Targeting smokers at higher lung cancer risk can improve efficiency and reduce false-positive detection in lung cancer screening. We evaluated whether time to first cigarette after waking (TTFC), a single-item measure of nicotine dependency, could improve stratification of lung cancer risk beyond standard smoking metrics (intensity, duration, and pack-years).

METHODS

In 3249 ever-smokers (n = 1812 case subjects; n = 1437 control subjects) from a population-based case-control study in Italy, we examined the association between TTFC and lung cancer using logistic regression and estimated lung cancer incidence by levels of TTFC, and intensity, duration, and pack-years using absolute risk regression. Significance tests were two-sided.

RESULTS

Compared with smokers with TTFC greater than 60 minutes, the lung cancer odds ratios for TTFC of 31 to 60 minutes, 6 to 30 minutes, and 5 or fewer minutes (by increasing dependency) were 2.57 (95% confidence interval [CI] = 2.03 to 3.26), 2.27 (95% CI = 1.79 to 2.88), and 3.50 (95% CI = 2.64 to 4.64), respectively (P trend < .0001). The average lung cancer incidence rates for smokers of 1 to 10, 11 to 20, 21 to 30 and more than 30 cigarettes per day were consistently higher among smokers with TTFC of 60 or fewer minutes vs more than 60 minutes (64.1 vs 11.7; 125.6 vs 28.6; 130.1 vs 40.7; and 260.8 vs 108.9 per 100000 person-years, respectively). The slopes of increase in lung cancer rates with smoking duration and pack-years were statistically significantly greater among smokers with higher dependency (P interaction < .001).

CONCLUSIONS

Lung cancer risk increases with shorter TTFC; this simple nicotine dependency measure increases lung cancer risk stratification beyond standard smoking measures. Assessing TTFC may improve lung cancer risk prediction and could be useful in lung cancer screening and smoking cessation programs.

Time to first cigarette predicts 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in adolescent regular and intermittent smokers, National Health and Nutrition and Examination Survey (NHANES) 2007-10

BACKGROUND AND AIMS

The time to first cigarette (TTFC) of the day is an indicator of nicotine intake in adults and adolescents. However, the relation between TTFC and biological markers of nicotine addiction and health risk in youths has not been well described. The current study examined whether an earlier TTFC predicts higher levels of a tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridal)-1 (NNAL), in regular and intermittent adolescent smokers and if this relation is mediated by nicotine intake (measured by cotinine) or cigarettes per day (CPD).

DESIGN

A cross-sectional analysis of a nationally representative subsample of adolescents.

SETTING

A general community sample from the 2007-08 and 2009-10 National Health and Nutrition and Examination Survey.

PARTICIPANTS

A total of 215 adolescents in the United States between the ages of 12 and 19 years who reported smoking at least once in the 5 days prior to data collection.

MEASUREMENTS

The primary outcome measure was urinary levels of NNAL.

FINDINGS

In both regular and intermittent smokers, earlier TTFC was associated dose-dependently with higher levels of NNAL (P < 0.03 in both cases). TTFC had an indirect effect on NNAL, mediated by nicotine intake (cotinine) in both regular [β = -0.08, standard error (SE) = 0.03, 95% confidence interval (CI) = -0.15, -0.03] and intermittent (β = -0.02, SE = 0.01, 95% CI = -0.05, -0.002) smokers. CPD was not found to be an important mediator of the relation between TTFC and NNAL.

CONCLUSIONS

Time between waking and the first cigarette of the day is correlated in daily and non-daily adolescent smokers with overall nicotine and therefore carcinogen intake.