Menthol smoking in relation to time to first cigarette and cotinine: results from a community-based study

Smoking timing, genetic susceptibility, and the risk of incident atrial fibrillation: a large prospective cohort study

AIMS

Although smoking is a well-known risk factor for atrial fibrillation (AF), the association of smoking timing with AF risk remains unclear. This study aimed to prospectively investigate the association of smoking timing with risk of incident AF, and test the modification effect of genetic susceptibility.

METHODS AND RESULTS

A total of 305,627 participants with detailed information for time from waking to first cigarette were enrolled from UK Biobank database. Cox proportional hazard model was employed to assess the relationship between smoking timing and AF risk. Weighted genetic risk score for AF was calculated. Over a median 12.2-year follow-up, 13,410 AF cases were documented. Compared to non-smokers, time from waking to the first cigarette showed gradient inverse associations with risk of incident AF (P-trend <0.001). The adjusted hazard ratio related to smoking timing was 1.13 (95% CI: 0.96-1.34) for >120 minutes, 1.20 (95% CI: 1.01-1.42) for 61-120 minutes, 1.34 (95% CI: 1.19-1.51) for 30-60 minutes, 1.43 (95% CI: 1.26-1.63) for 5-15 minutes, and 1.49 (95% CI: 1.24-1.63) for <5 minutes, respectively. Additionally, we found that the increased risk of AF related to shorter time from waking to the first cigarette was strengthened by the genetic susceptibility to AF.

CONCLUSIONS

Our findings suggest gradient inverse association between time from waking to the first cigarette and risk of incident AF, and the association is strengthened by the genetic susceptibility to AF.

The Effects of Changes in Cigarette Menthol Content on Acute Nicotine Pharmacology and Smoking Topography

INTRODUCTION

Menthol influences the appeal and addictiveness of cigarette smoking, however the data regarding menthol's effects on nicotine pharmacokinetics (PK) and smoking topography are inconsistent. This study investigated the impact of different cigarette menthol levels on nicotine pharmacology and smoking topography in current menthol smokers.

AIMS AND METHODS

The study was a double-blind, randomized, four-period, crossover study to investigate the effects of smoking cigarettes with varying menthol content (0, 3, 6, and 12 mg menthol) on nicotine PK, smoking topography, and subjective effects in current menthol smokers. Each experimental session consisted of a prescribed use session, followed by 145 min of no smoking and a 1-h ad libitum smoking session. Serial blood samples were collected; smoking topography was recorded using CReSS Lab topography device.

RESULTS

There was no significant effect of menthol on nicotine PK after prescribed smoking of cigarettes with varying menthol contents. During ad libitum smoking, there was significantly smaller total puff volume and puff duration in the 12 mg menthol condition compared to other menthol conditions. Subjective and sensory measures indicated significantly higher overall positive ratings for the 3 mg and 6 mg menthol cigarettes compared to the 0 mg menthol cigarette; the 12 mg menthol cigarette was less liked and harsher than the 3 mg condition.

CONCLUSIONS

These findings suggest that menthol, at concentrations reflecting the marketplace (3-6 mg), contributes to positive subjective smoking experiences among menthol smokers, but does not have a significant effect on nicotine PK or smoking topography in an acute laboratory setting.

IMPLICATIONS

While our data indicate that varying menthol content does not have a significant impact on nicotine's pharmacological effects under acute exposure conditions, these data highlight the contribution of menthol's flavor and sensory effects to product preference and positive smoking experiences, which facilitate repeated experimentation, progression to regular use, and subsequent dependence.

Menthol Smoking and Nicotine Dependence among Black/African American Women Smokers Living in Low-Resource, Rural Communities

Black/African American women from low-resource, rural communities bear a disproportionate burden of tobacco-related morbidity and mortality. This study examined associations between menthol smoking and socioeconomic deprivation with nicotine dependence and quitting behaviors among Black/African American women cigarette and/or little cigar/cigarillo smokers, aged 18–50 living in low-resource, rural communities. Baseline survey data from a randomized controlled behavioral/intervention trial (#NCT03476837) were analyzed (n = 146). Outcomes included time to first tobacco product (cigarette/little cigar/cigarillo) use within 5 min of waking, Fagerstrom Test for Nicotine Dependence (FTND) score, and ever attempting to quit cigarettes. Socioeconomic deprivation measures included education, income, and receiving supplemental nutritional assistance (SNAP) program benefits. In adjusted regression analyses, menthol smoking was associated with both greater FTND scores and time to first tobacco product use within 5 min of waking, but not ever attempting to quit cigarettes. Regardless of menthol status, only 25.0% of smokers reported that they would quit smoking if menthol cigarettes were banned. The proportion of smokers who smoked their first tobacco product within 5 min of waking increased slightly with greater socioeconomic deprivation. Additional research and targeted efforts are needed to reduce nicotine dependence among Black/African American women smokers living in rural, low-resource communities where access to cessation services is limited.

Time to First Cigarette: A Potential Clinical Screening Tool for Nicotine Dependence

OBJECTIVES

The time to first cigarette (TTFC) of the day has been identified as the best single-item indicator of nicotine dependence. However, TTFC has not been extensively used in clinical settings and is not a criterion for tobacco use disorder, perhaps due to a lack of information about TTFC's predictive value. This review provides a synthesis of the accumulating literature on TTFC's relationships with nicotine dependence, identify gaps, and inform future clinical and epidemiologic research of potential uses of TTFC.

METHODS

A systematic review of the literature was conducted using PubMed, Google Scholar, and Web of Science ISI databases. We identified 16 articles examining the relation between TTFC and negative outcomes associated with high levels of nicotine addiction and Tobacco Use Disorders (eg, high levels of nicotine and toxicant exposure, progressive use over time, failed cessation, head-and-neck cancers).

RESULTS

Earlier TTFC was consistently associated with greater likelihood of cessation failure and relapse, and higher levels of biomarkers of tobacco exposure. Several of these associations were found among both adult and adolescent smokers, and remained even after accounting for smoking behaviors (eg, cigarettes/day).

CONCLUSIONS

Earlier TTFC is a key indicator of greater nicotine dependence. Knowledge of a smoker's TTFC may allow clinicians to accurately inform smokers of health risks and assign greater resources during cessation attempts. Smokers may be able to use TTFC to self-select cessation aids and accurately assess their unique smoking-related health risks. TTFC may be a better item than cigarettes/day for accurately quantifying dependence and risk in epidemiologic studies.

Characterizing nicotine exposure among a community sample of non-daily smokers in the United States

Background

Over one-quarter of all smokers in the United States identify as non-daily smokers and this number is projected to rise. Unlike daily smokers who typically maintain consistent levels of nicotine exposure with regular smoking, non-daily smokers have variable patterns of smoking that likely result in high intraindividual variability in nicotine intake. The current study aimed to characterize the weekly intraindividual variability in cotinine and identify smoking-related predictors in nondaily smokers.

Methods

An ecological momentary assessment of 60 non-daily smokers ages 24–57 years was conducted over a consecutive 7-day at-home protocol to log each smoking session, assessments of mood and social activity during smoking, and collection of daily saliva samples in a convenience sample from Pennsylvania, USA. Hierarchical linear regression analyses were conducted to determine the effects of smoking characteristics on total cotinine exposure measured by pharmacokinetic area under the curve and the range, maximum, and minimum cotinine values during the week controlling for demographic variables.

Results

The mean daily cotinine level was 119.2 ng/ml (SD = 168.9) with individual values that ranged from nondetectable to 949.6 ng/ml. Menthol predicted increased total cotinine levels (P < 0.05). Shorter time to the first cigarette of the day predicted significantly higher minimum (P < 0.05), maximum (P < 0.05), and total cotinine values (P < 0.05) after controlling for covariates. Negative emotions and social interactions with others were also significantly associated with higher cotinine metrics. There was no significant effect of the nicotine metabolite ratio.

Conclusions

Our findings highlight the variability in nicotine exposure across days among non-daily smokers and point to the role of smoking context in nicotine exposure. The findings suggest the need to develop better assessment methods to determine health and dependence risk and personalized cessation interventions for this heterogeneous and growing group of smokers.

Health Care Utilization of Menthol and Non-menthol Cigarette Smokers

INTRODUCTION

To study the association between health care utilization and menthol cigarette use and whether the association differed between African American (AA) and non-AA smokers.

METHODS

We analyzed the three most recent 2005, 2010, and 2015 National Health Interview Survey Cancer Control Supplements. After incorporating propensity score weights adjusting for observed differences between menthol and non-menthol users, we estimated Zero-Inflated Poisson models on hospital nights, emergency department visits, doctor visits, and home visits as a function of menthol use status and other covariates separately for current cigarette smokers and recent quitters (former smokers quitting cigarette smoking ≤ 4 years).

RESULTS

Although current menthol smokers smoked fewer cigarettes per day than current non-menthol smokers, they did not differ from current non-menthol smokers in health care utilization. Among recent quitters, those who used to smoke menthol cigarettes had higher odds of having hospital nights than those who used to smoke non-menthol cigarettes. However, we did not find any significant association between menthol use and other health care utilization-emergency department visits, doctor visits, and home visits-among recent quitters. Moreover, compared with non-AA recent quitters, AA recent quitters had higher odds of having home visits, but fewer home visits, if they used to smoke menthol cigarettes.

CONCLUSION

Menthol use was associated with greater hospitalization among recent quitters, and the association between home visits and menthol use differed between AA and non-AA recent quitters.

IMPLICATIONS

This is the first study that used econometric models to study the association between health care utilization and menthol cigarette use and examine whether the association differed between AA and non-AA smokers. Our study found health care utilization did not differ by menthol use status for current smokers, although current menthol smokers smoked fewer cigarettes per day than current non-menthol smokers. However, we found menthol use was associated with higher odds of having hospital nights for recent quitters. We also found AA recent quitters had a different association between home visits and menthol use compared with non-AA recent quitters.

Menthol Cigarettes, Tobacco Dependence, and Smoking Persistence: The Need to Examine Enhanced Cognitive Functioning as a Neuropsychological Mechanism

INTRODUCTION

Despite the overall decline in the prevalence of cigarette use in the United States, menthol cigarette use among smokers is rising, and evidence shows that it may lead to more detrimental effects on public health than regular cigarette use. One of the mechanisms by which nicotine sustains tobacco use and dependence is due to its cognitive enhancing properties, and basic science literature suggests that menthol may also enhance nicotine's acute effect on cognition.

AIMS AND METHODS

The purpose of this review is to suggest that the cognitive enhancing effects of menthol may be a potentially important neuropsychological mechanism that has yet to be examined. In this narrative review, we provide an overview of basic science studies examining neurobiological and cognitive effects of menthol and menthol cigarette smoking. We also review studies examining menthol essential oils among humans that indicate menthol alone has acute cognitive enhancing properties. Finally, we present factors influencing the rising prevalence of menthol cigarette use among smokers and the importance of this gap in the literature to improve public health and smoking cessation treatment.

CONCLUSIONS

Despite the compelling evidence for menthol's acute cognitive enhancing and reinforcing effects, this mechanism for sustaining tobacco dependence and cigarette use has yet to be examined and validated among humans. On the basis of the basic science evidence for menthol's neurobiological effects on nicotinic receptors and neurotransmitters, perhaps clarifying menthol's effect on cognitive performance can help to elucidate the complicated literature examining menthol and tobacco dependence.

IMPLICATIONS

Menthol cigarette use has continued to be a topic of debate among researchers and policy makers, because of its implications for understanding menthol's contribution to nicotine dependence and smoking persistence, as well as its continued use as a prevalent flavoring in tobacco and nicotine products in the United States and internationally. As international tobacco regulation policies have begun to target menthol cigarettes, research studies need to examine how flavoring additives, specifically menthol, may acutely influence neurobiological and cognitive functioning as a potential mechanism of sustained smoking behavior to develop more effective treatments.

Measures of dependence in menthol and nonmenthol smokers - A comprehensive narrative review

Introduction. More than a decade ago, concerns were raised that menthol in cigarettes might enhance addiction to smoking. This article provides a comprehensive review of published studies examining cigarette dependence among menthol and nonmenthol smokers. The purpose of the review is to evaluate the scientific evidence to determine if menthol increases cigarette dependence. Materials and Methods. The published literature was searched in 2019 for studies that provide evidence on cigarette dependence among menthol compared to nonmenthol smokers. Included in this review are published studies that compare menthol and nonmenthol smokers based on widely accepted and validated measures of dependence, or other established predictors of dependence (age of smoking initiation [first cigarette]/age of progression [regular/daily smoking]) and indicators of dependence (smoking frequency, cigarettes smoked per day, time to first cigarette after waking, night waking to smoke, smoking duration). Results and Conclusion. Based on a review of the available studies, including those with adjusted results and large representative samples, reliable and consistent empirical evidence supports a conclusion that menthol smokers are not more dependent than nonmenthol smokers and thus menthol in cigarettes does not increase dependence.

Menthol cigarette smoking is associated with greater subjective reward, satisfaction, and "throat hit", but not greater behavioral economic demand

AIMS

The cooling and minty flavor of menthol in cigarettes has been hypothesized to mask the harshness of inhaled cigarette smoke, contributing to menthol's appeal and subjective reinforcement and linking menthol use to smoking initiation, progression, nicotine dependence, and difficulty quitting. This study examined differences between menthol and non-menthol smokers on behavioral economic indices of reinforcing efficacy (i.e., demand) and subjective response to smoking (i.e., satisfaction, reward, "throat hit," aversion) and the association between measurements of reinforcement and subjective response.

DESIGN

600 current adult smokers were recruited from an online smoking cessation program. Following website enrollment, individuals completed a self-report measurement of subjective response to smoking (reward, satisfaction, aversion, "throat hit"), and a modified cigarette purchase task (CPT) to assess behavioral economic cigarette demand.

FINDINGS

In bivariate and adjusted ANOVA models, menthol smokers reported greater subjective reward, satisfaction, and positive sensations in the throat ("throat hit") from smoking compared to non-menthol smokers; and those outcomes were also correlated with greater nicotine dependence and lower likelihood of a past-year quit attempt. Although cigarette demand was associated with smoking level, subjective smoking reward, and nicotine dependence, there were no differences in smoking demand between menthol vs. non-menthol smokers.

CONCLUSIONS

The pleasurable aspects of menthol vs non-menthol smoking may be a mechanism linking it to greater nicotine dependence and difficulty quitting. A menthol ban could decrease population-level cigarette consumption by restricting smokers' access to a highly rewarding cigarette flavoring.

Harm Perceptions of Menthol and Nonmenthol Cigarettes Differ by Brand, Race/Ethnicity, and Gender in US Adult Smokers: Results from PATH Wave 1

INTRODUCTION

Harm perceptions of menthol cigarettes may contribute to their appeal and use. African-Americans, women, and younger smokers disproportionately use menthol cigarettes, and may misperceive harm of menthol cigarettes.

METHODS

Data were from Wave 1 of the Population Assessment of Tobacco and Health (PATH) Study. Weighted analyses of current adult smokers (18 and older) were used to estimate the correlates of menthol smoking among all cigarette brands and separately for the top three cigarette brands (Newport, Camel, and Marlboro). Adjusted models examined the main effect of menthol smoking on harm perceptions of one's own brand of cigarette and interactions with race/ethnicity, age, and gender.

RESULTS

Menthol cigarettes were used by nearly 40% of current smokers, although the prevalence of menthol smoking differed across the top three brands (94% Newport, 46% Camel, and 18% Marlboro). Among menthol smokers, 80% perceived their cigarette as equally harmful, 14% perceived their brand as more harmful, and 7% perceived their brand as less harmful. In adjusted models, menthol smokers were more likely than nonmenthol smokers to misperceive their own brand as more harmful than other brands (compared to no difference in harm). Race and gender emerged as moderators of the association between menthol brand preference and harm perceptions.

CONCLUSIONS

In adjusted analyses, menthol smokers were more likely than nonmenthol smokers to perceive their brand as more harmful than other brands, with differences by sub-groups who disproportionately use menthol.

IMPLICATIONS

Menthol cigarettes have been historically marketed with messages conveying lower harm than other cigarettes. Little is known about how contemporary adult menthol smokers perceive the harm of their usual brand, and potential differences by race, gender, and young adult versus older adult age group. After adjusting for other factors, menthol smokers were more likely than nonmenthol smokers to perceive their cigarette brand as more harmful than other brands. Further, the association between menthol smoking and harm perceptions differed by race and gender, but not by age group (young adult vs. older adult). This type of large-scale study identifies critical links between menthol smoking and harm perceptions among vulnerable smokers that will inform regulatory actions designed to decrease smoking-related harm.

Menthol enhances nicotine-induced locomotor sensitization and in vivo functional connectivity in adolescence

Mentholated cigarettes capture a quarter of the US market, and are disproportionately smoked by adolescents. Menthol allosterically modulates nicotinic acetylcholine receptor function, but its effects on the brain and nicotine addiction are unclear. To determine if menthol is psychoactive, we assessed locomotor sensitization and brain functional connectivity. Adolescent male Sprague Dawley rats were administered nicotine (0.4 mg/kg) daily with or without menthol (0.05 mg/kg or 5.38 mg/kg) for nine days. Following each injection, distance traveled in an open field was recorded. One day after the sensitization experiment, functional connectivity was assessed in awake animals before and after drug administration using magnetic resonance imaging. Menthol (5.38 mg/kg) augmented nicotine-induced locomotor sensitization. Functional connectivity was compared in animals that had received nicotine with or without the 5.38 mg/kg dosage of menthol. Twenty-four hours into withdrawal after the last drug administration, increased functional connectivity was observed for ventral tegmental area and retrosplenial cortex with nicotine+menthol compared to nicotine-only exposure. Upon drug re-administration, the nicotine-only, but not the menthol groups, exhibited altered functional connectivity of the dorsal striatum with the amygdala. Menthol, when administered with nicotine, showed evidence of psychoactive properties by affecting brain activity and behavior compared to nicotine administration alone.

Menthol cigarettes and the public health standard: a systematic review

Background

Although menthol was not banned under the Tobacco Control Act, the law made it clear that this did not prevent the Food and Drug Administration from issuing a product standard to ban menthol to protect public health. The purpose of this review was to update the evidence synthesis regarding the role of menthol in initiation, dependence and cessation.

Methods

A systematic review of the peer-reviewed literature on menthol cigarettes via a PubMed search through May 9, 2017. The National Cancer Institute’s Bibliography of Literature on Menthol and Tobacco and the FDA’s 2011 report and 2013 addendum were reviewed for additional publications. Included articles addressing initiation, dependence, and cessation were synthesized based on study design and quality, consistency of evidence across populations and over time, coherence of findings across studies, and plausibility of the findings.

Results

Eighty-two studies on menthol cigarette initiation (n = 46), dependence (n = 14), and cessation (n = 34) were included. Large, representative studies show an association between menthol and youth smoking that is consistent in magnitude and direction. One longitudinal and eight cross-sectional studies demonstrate that menthol smokers report increased nicotine dependence compared to non-menthol smokers. Ten studies support the temporal relationship between menthol and reduced smoking cessation, as they measure cessation success at follow-up.

Conclusions

The strength and consistency of the associations in these studies support that the removal of menthol from cigarettes is likely to reduce youth smoking initiation, improve smoking cessation outcomes in adult smokers, and in turn, benefit public health.

Electronic supplementary material

The online version of this article (10.1186/s12889-017-4987-z) contains supplementary material, which is available to authorized users.

Determining non-cigarette tobacco, alcohol, and substance use typologies across menthol and non-menthol smokers using latent class analysis

Background

Substance use and mental health are robustly associated with smoking and poor cessation outcomes, but not often examined in combination with menthol cigarette smoking, which is also associated with lower quit rates. This study identified classes of Black and White menthol and non-menthol cigarette smokers based on demographics, alcohol, drug, and other tobacco use behaviors.

Methods

Using screening data from two studies, latent class analysis (LCA) was conducted to classify n = 1177 menthol and non-menthol cigarette smokers on demographic characteristics, heavy smoking, alcohol and drug use, desire to quit smoking, other tobacco product use, and use of psychotropic medication.

Results

Three latent classes were identified that differentiated smokers on substance use, menthol cigarette smoking, and other tobacco use behavior. One class consisted primarily of young adults who used a wide array of other tobacco products, reported the highest prevalence of other drug use, and showed the lowest desire to quit smoking cigarettes in the next 6-months. Class 2 comprised primarily of Black male menthol smokers, all of whom used cigarillos in addition to cigarettes, and who displayed moderate drug use. The third class was categorized as primarily older cigarette smokers, who engaged in very little other tobacco use or drug use, but who were most likely to self-report being prescribed psychotropic medication.

Conclusions

LCA allowed for the identification of distinct classes of smokers based on factors related to poor cessation outcomes, including menthol use, that have not previously been examined in combination. Interventions should target specific groups of smokers, rather than take a “one size fits all” approach.

Impact of Menthol Smoking on Nicotine Dependence for Diverse Racial/Ethnic Groups of Daily Smokers

Introduction: The aims of this study were to evaluate whether menthol smoking and race/ethnicity are associated with nicotine dependence in daily smokers. Methods: The study used two subsamples of U.S. daily smokers who responded to the 2010–2011 Tobacco Use Supplement to the Current Population Survey. The larger subsample consisted of 18,849 non-Hispanic White (NHW), non-Hispanic Black (NHB), and Hispanic (HISP) smokers. The smaller subsample consisted of 1112 non-Hispanic American Indian/Alaska Native (AIAN), non-Hispanic Asian (ASIAN), non-Hispanic Hawaiian/Pacific Islander (HPI), and non-Hispanic Multiracial (MULT) smokers. Results: For larger (smaller) groups the rates were 45% (33%) for heavy smoking (16+ cig/day), 59% (51%) for smoking within 30 min of awakening (Sw30), and 14% (14%) for night-smoking. Overall, the highest prevalence of menthol smoking corresponded to NHB and HPI (≥65%), followed by MULT and HISP (31%–37%), and then by AIAN, NHW, and ASIAN (22%–27%) smokers. For larger racial/ethnic groups, menthol smoking was negatively associated with heavy smoking, not associated with Sw30, and positively associated with night-smoking. For smaller groups, menthol smoking was not associated with any measure, but the rates of heavy smoking, Sw30, and night-smoking varied across the groups. Conclusions: The diverse associations between menthol smoking and nicotine dependence maybe due to distinction among the nicotine dependence measures, i.e., individually, each measure assesses a specific smoking behavior. Menthol smoking may be associated with promoting smoking behaviors.

Comparisons of three nicotine dependence scales in a multiethnic sample of young adult menthol and non-menthol smokers

BACKGROUND

Few studies have compared nicotine dependence among menthol and non-menthol cigarette smokers in a multiethnic sample of young adult daily cigarette smokers. This study examines differences in nicotine dependence among menthol and non-menthol daily smokers and the associations of nicotine dependence with quitting behaviors among Native Hawaiian, Filipino, and White cigarette smokers aged 18-35.

METHODS

Craigslist.org, newspaper advertisements, and peer-to-peer referrals were used to recruit daily smokers (n = 186) into a lab-based study. Nicotine dependence was assessed using the Fagerstrom Test of Nicotine Dependence (FTND), the Nicotine Dependence Syndrome Scale (NDSS), and the brief Wisconsin Inventory for Smoking Dependence Motives (WISDM). Multiple regression analyses were used to examine differences in nicotine dependence between menthol and non-menthol smokers and the relationship between each nicotine dependence scale with self-efficacy to quit, quit attempt in the past 12 months, and number of attempts.

RESULTS

Menthol smokers were more likely to report difficulty refraining from smoking in places where forbidden (p = .04) and had higher scores on social/environmental goads subscale of the WISDM (p = .0005). Two-way interaction models of the FTND and menthol status showed that menthol smokers with higher levels of dependence were more likely to have tried to quit smoking in the past 12 months (p = .02), but were less likely to have had multiple quit attempts (p = .01).

CONCLUSIONS

Components of the FTND and WISDM distinguish levels of dependence between menthol and non-menthol smokers. Higher FTND scores were associated with having a quit attempt, but fewer quit attempts among menthol smokers.

Predictors, indicators, and validated measures of dependence in menthol smokers

This article presents a comprehensive review of the menthol cigarette dependence-related literature and results from an original analysis of the Total Exposure Study (TES), which included 1,100 menthol and 2,400 nonmenthol adult smokers. The substantial scientific evidence available related to age of first cigarette, age of regular use, single-item dependence indicators (smoking frequency, cigarettes per day, time to first cigarette, night waking to smoke), smoking duration, numerous validated and widely accepted measures of nicotine/cigarette dependence, and our analysis of the TES do not support that menthol smokers are more dependent than nonmenthol smokers or that menthol increases dependence.

Menthol facilitates the intravenous self-administration of nicotine in rats

Menthol is preferred by ~25% of smokers and is the most common flavoring additive in tobacco and electronic cigarettes. Although some clinical studies have suggested that menthol facilitates the initiation of smoking and enhances the dependence on nicotine, many controversies remain. Using licking as the operant behavior, we found that adolescent rats self-administering nicotine (30μg/kg/infusion, free base, i.v.) with contingent oral menthol (60μl, 0.01% w/v) obtained significantly more infusions than rats receiving a vehicle cue or rats self-administering i.v. saline with a menthol cue. Rats yoked to their menthol-nicotine masters emitted significantly fewer licks on the active spouts, indicating that contingent pairing between nicotine and menthol is required for sustained nicotine intake. Rats that self-administered nicotine with a menthol cue also exhibited a long-lasting extinction burst and robust reinstatement behavior, neither of which were observed in rats that self-administered saline with a menthol cue. The cooling sensation of menthol is induced by activating the transient receptor potential M8 (TRPM8) channel. When WS-23, an odorless agonist of the TRPM8 channel, was used as a contingent cue for nicotine, the rats obtained a similar number of nicotine infusions as the rats that were provided a menthol cue and exhibited a strong preference for the active spout. In contrast, highly appetitive taste and odor cues failed to support nicotine self-administration. These data indicated that menthol, likely by inducing a cooling sensation, becomes a potent conditioned reinforcer when it is contingently delivered with nicotine. Together, these results provide a key behavioral mechanism by which menthol promotes the use of tobacco products or electronic cigarettes.

Smoking and prostate cancer in a multi-ethnic cohort

BACKGROUND

Prostate cancer (PCa) and smoking-related morbidity disproportionately burdens African American (AA) men. Smoking is associated with high-grade PCa and incidence, but few studies have focused on AA men. This study aims to determine the effect of tobacco-use on odds of PCa and of high-grade PCa in a population of predominantly AA men.

METHODS

This is a cross-sectional study evaluating smoking and PCa status in men with incident PCa and screened healthy controls. Altogether, 1,085 men (527 cases and 558 controls), age ≥ 40 years were enrolled through outpatient urology clinics in two US cities from 2001 to 2012. Validated questionnaires were used to gather clinical and socioeconomic data.

RESULTS

The cases and controls were predominantly AA (79.9% and 71.3%, respectively, P = 0.01). AA men smoked more frequently (53.4% vs. 47.9%, P < 0.001) and quit less frequently than European American (EA) men (31.5% vs. 40.4%, P = 0.01). AA heavy smokers had increased odds of PCa diagnosis (OR 2.57, 95% CI 1.09, 6.10) and high-grade cancer (OR 1.89, 95% CI 1.03, 3.48) relative to never smokers and light smokers. Among AAs, heavy smokers had lower odds of NCCN low PCa recurrence risk stratification. AA former smokers had a trend for increased odds of high-grade cancer compared to never smokers. The associations between smokings, cancer diagnosis and cancer grade did not reach statistical significance in EA men.

CONCLUSION

We found ethnic differences in smoking behavior. Heavy smoking is associated with increased odds of PCa and of higher Gleason grade in AA men.