Pulmonary Health Effects of Electronic Cigarettes: A Scoping Review

Association of cigarette and electronic cigarette use patterns with all-cause mortality: A national cohort study of 145,390 US adults

OBJECTIVE

While e-cigarette use is associated with adverse cardiopulmonary health effects, the mortality risks associated with e-cigarette use alone and combined with smoking remain unexamined.

METHODS

Data between 2014 and 2018 were obtained from the National Health Interview Survey (NHIS), an annual cross-sectional survey of US adults. All-cause mortality and date of death were obtained via linkage of the NHIS to the National Death Index through December 31, 2019. A 6-category composite cigarette (never, former, current) and e-cigarette (current, non-current) exposure variable was created. We examined the association of cigarette and e-cigarette use patterns with all-cause mortality using adjusted Cox models.

RESULTS

Among 145,390 participants (79,294 women [51.5%]; 60,560 aged 18-44 [47.4%]), 5220 deaths were observed over a median follow-up of 3.5 years (508,545 total person-years). Dual use of cigarettes and e-cigarettes was associated with higher mortality risk compared with non-current e-cigarette use in combination with never smoking (hazard ratio [HR] 2.44; 95% CI, 1.90-3.13) and had a risk that did not differ from current exclusive smoking (HR, 1.06; 95% CI, 0.83-1.37). Current e-cigarette use in combination with former smoking was associated with a lower mortality risk than current exclusive cigarette smoking (HR 0.64; 95% CI, 0.41-0.99).

CONCLUSIONS

The addition of e-cigarette use to smoking does not reduce mortality risk compared with exclusive smoking. However, transitioning completely from cigarettes to e-cigarettes may be associated with mortality risk reduction. Further research is needed to verify these findings in larger cohorts and over longer periods of follow-up.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. People who smoke, healthcare providers and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review.

OBJECTIVES

To examine the safety, tolerability and effectiveness of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence, in comparison to non-nicotine EC, other smoking cessation treatments and no treatment.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register to 1 February 2023, and Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 July 2023, and reference-checked and contacted study authors.

SELECTION CRITERIA

We included trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention as these studies have the potential to provide further information on harms and longer-term use. Studies had to report an eligible outcome.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Critical outcomes were abstinence from smoking after at least six months, adverse events (AEs), and serious adverse events (SAEs). We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in pairwise and network meta-analyses (NMA).

MAIN RESULTS

We included 88 completed studies (10 new to this update), representing 27,235 participants, of which 47 were randomized controlled trials (RCTs). Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 58 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There is high certainty that nicotine EC increases quit rates compared to nicotine replacement therapy (NRT) (RR 1.59, 95% CI 1.29 to 1.93; I2 = 0%; 7 studies, 2544 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6 more). There is moderate-certainty evidence (limited by imprecision) that the rate of occurrence of AEs is similar between groups (RR 1.03, 95% CI 0.91 to 1.17; I2 = 0%; 5 studies, 2052 participants). SAEs were rare, and there is insufficient evidence to determine whether rates differ between groups due to very serious imprecision (RR 1.20, 95% CI 0.90 to 1.60; I2 = 32%; 6 studies, 2761 participants; low-certainty evidence). There is moderate-certainty evidence, limited by imprecision, that nicotine EC increases quit rates compared to non-nicotine EC (RR 1.46, 95% CI 1.09 to 1.96; I2 = 4%; 6 studies, 1613 participants). In absolute terms, this might lead to an additional three quitters per 100 (95% CI 1 to 7 more). There is moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 1840 participants). There is insufficient evidence to determine whether rates of SAEs differ between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 9 studies, 1412 participants; low-certainty evidence). Due to issues with risk of bias, there is low-certainty evidence that, compared to behavioural support only/no support, quit rates may be higher for participants randomized to nicotine EC (RR 1.88, 95% CI 1.56 to 2.25; I2 = 0%; 9 studies, 5024 participants). In absolute terms, this represents an additional four quitters per 100 (95% CI 2 to 5 more). There was some evidence that (non-serious) AEs may be more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low-certainty evidence; 4 studies, 765 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 0.89, 95% CI 0.59 to 1.34; I2 = 23%; 10 studies, 3263 participants; very low-certainty evidence). Results from the NMA were consistent with those from pairwise meta-analyses for all critical outcomes, and there was no indication of inconsistency within the networks. Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons, hence, evidence for these is limited, with CIs often encompassing both clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain due to risk of bias inherent in the study design. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but the longest follow-up was two years and the number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

E-cigarette use and respiratory symptoms in adults: A systematic review and meta-analysis

INTRODUCTION

Electronic cigarette (e-cigarette) use is gaining popularity among adults. Monitoring e-cigarette-induced respiratory symptoms is crucial for both clinical and regulatory purposes. We systematically reviewed the current literature to understand the prevalence of respiratory symptoms among exclusive e-cigarette users, dual users, and former smokers.

METHODS

Databases searched included PubMed, CINAHL, Cochrane Library, Embase, and Scopus. We included all English-language, empirical quantitative articles that explored the prevalence of e-cigarette-related respiratory symptoms. Random-effects models were utilized in conducting the meta-analyses. The quality of identified studies was evaluated using the NIH Study Quality Assessment Tools. This study is registered with PROSPERO(#CRD42020165973).

RESULTS

The literature search identified 1240 references. After removing duplicates and screening for eligibility, 168 studies were included in the final review. The majority of included studies reported a wide range of adverse respiratory symptoms. The respiratory symptoms were prevalent among the exclusive e-cigarette users, dual users, and those who switched from combustible cigarettes to e-cigarettes. Further, out of the RCT studies, 5 were rated as good quality, while 3 were rated as fair. Among the observational studies, 24 were rated as good quality, and 9 were rated as fair. The two experimental studies were both rated as fair quality.

CONCLUSIONS

Continued monitoring of respiratory symptoms among e-cigarette users is warranted. Due to the heterogeneity and inconsistencies among studies, which limit result interpretation and highlight the need for studies assessing causal inference, further research using robust study designs is essential. This will provide clinicians with comprehensive knowledge about the potential respiratory risks of e-cigarette use.

Nicotine affects mitochondrial structure and function in human airway smooth muscle cells

Exposure to cigarette smoke and e-cigarettes, with nicotine as the active constituent, contributes to increased health risks associated with asthma. Nicotine exerts its functional activity via nicotinic acetylcholine receptors (nAChRs), and the alpha7 subtype (α7nAChR) has recently been shown to adversely affect airway dynamics. The mechanisms of α7nAChR action in airways, particularly in the context of airway smooth muscle (ASM), a key cell type in asthma, are still under investigation. Mitochondria have garnered increasing interest for their role in regulating airway tone and adaptations to cellular stress. Here mitochondrial dynamics such as fusion versus fission, and mitochondrial Ca2+ ([Ca2+]m), play an important role in mitochondrial homeostasis. There is currently no information on effects and mechanisms by which nicotine regulates mitochondrial structure and function in ASM in the context of asthma. We hypothesized that nicotine disrupts mitochondrial morphology, fission-fusion balance, and [Ca2+]m regulation, with altered mitochondrial respiration and bioenergetics in the context of asthmatic ASM. Using human ASM (hASM) cells from nonasthmatics, asthmatics, and smokers, we examined the effects of nicotine on mitochondrial dynamics and [Ca2+]m. Fluorescence [Ca2+]m imaging of hASM cells with rhod-2 showed robust responses to 10 μM nicotine, particularly in asthmatics and smokers. In both asthmatics and smokers, nicotine increased the expression of fission proteins while decreasing fusion proteins. Seahorse analysis showed blunted oxidative phosphorylation parameters in response to nicotine in these groups. α7nAChR siRNA blunted nicotine effects, rescuing [Ca2+]m, changes in mitochondrial structural proteins, and mitochondrial dysfunction. These data highlight mitochondria as a target of nicotine effects on ASM, where mitochondrial disruption and impaired buffering could permit downstream effects of nicotine in the context of asthma.NEW & NOTEWORTHY Asthma is a major healthcare burden, which is further exacerbated by smoking. Recognizing the smoking risk of asthma, understanding the effects of nicotine on asthmatic airways becomes critical. Surprisingly, the mechanisms of nicotine action, even in normal and especially asthmatic airways, are understudied. Accordingly, the goal of this research is to investigate how nicotine influences asthmatic airways in terms of mitochondrial structure and function, via the a7nAChR.

Electronic Cigarette Harms: Aggregate Evidence Shows Damage to Biological Systems

Evidence of the harms of e-cigarettes has been unfolding slowly and has been documented in many reviews and reports worldwide. A narrative review of new evidence is presented since, as research has continued, newly aggregated evidence of the dangers of electronic cigarettes on the brain, heart, and lungs is vital to inform decisions on restricting the use of e-cigarettes. Several biomedical research databases were searched for electronic cigarette health effects, emphasizing reviews, systematic reviews, and meta-analyses. Over 50 review studies, primarily in 2022 and 2023, illustrate some of the latest information on e-cigarette harms. Results show studies of respiratory, neurological, and cardiovascular effects. Researchers call for expanding studies through new methods to elaborate on initial findings of multiple harms emerging in clinical investigations. Since the use of electronic cigarettes for adult cessation is not sanctioned in most countries, it is clear that health authorities see significant costs to the health of the general population if the promotion and use of electronic cigarettes occur worldwide. Regulatory action to control electronic cigarettes should consider the substantial evidence of electronic cigarette harm.

The relationship between chronic lung disease diagnosis and the susceptibility to e-cigarette use in adults: The mediation effects of psychosocial, cognitive influences, and the moderation effect of physiological factors

INTRODUCTION

There is a paucity of studies on e-cigarette use among adults with chronic lung disease. In the present study, we aimed to assess whether psychosocial or cognitive factors elucidate the relationship between chronic lung disease (CLD) and susceptibility to e-cigarette use and whether the relationship between CLD and e-cigarette use is conditional on the presence of respiratory symptoms.

METHODS

We recruited adults aged ≥18 years in Alabama with CLD from university medical clinics (n=140) and individuals without CLD (n=123 as a reference group). Information on sociodemographics, susceptibility to e-cigarette use, psychosocial factors, and cognitive factors were collected. Mediation analysis was used to assess whether the psychosocial factors or cognitive factors explained the association between CLD and susceptibility to using e-cigarettes, and moderation analysis was conducted to determine if respiratory factors would change the association between CLD and susceptibility to e-cigarette use.

RESULTS

Psychosocial factors (stress, depression, anxiety) and e-cigarette positive expectancy were notably high among individuals with CLD. Having CLD was associated with a lower likelihood of susceptibility to e-cigarette use. Higher levels of stress, being a smoker, boredom, taste/sensorimotor manipulation, and social facilitation were associated with higher odds of susceptibility to using e-cigarettes among individuals with CLD. Mediation analysis indicated a statistically significant indirect effect of CLD on the susceptibility to using e-cigarettes through stress and boredom reduction. We did not find a statistically significant interaction between CLD and respiratory symptoms affecting susceptibility to using e-cigarettes.

CONCLUSIONS

Individuals with CLD often exhibit stress, depression, and a positive view of e-cigarettes but are generally less inclined to use them. Stress, smoking habits, boredom, taste, and social influence can increase their susceptibility to e-cigarette use. Our findings call for further exploration to evaluate the temporal relationship between CLD status, psychosocial factors, cognitive factors, and susceptibility to using e-cigarettes.

TRIAL REGISTRATION

The study was registered on ClinicalTrials.gov, on 5 November 2019. Identifier: NCT04151784.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. Some people who smoke use ECs to stop or reduce smoking, although some organizations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review.

OBJECTIVES

To examine the effectiveness, tolerability, and safety of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 July 2022, and reference-checked and contacted study authors.  SELECTION CRITERIA: We included randomized controlled trials (RCTs) and randomized cross-over trials, in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. Studies had to report abstinence from cigarettes at six months or longer or data on safety markers at one week or longer, or both.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, adverse events (AEs), and serious adverse events (SAEs). Secondary outcomes included the proportion of people still using study product (EC or pharmacotherapy) at six or more months after randomization or starting EC use, changes in carbon monoxide (CO), blood pressure (BP), heart rate, arterial oxygen saturation, lung function, and levels of carcinogens or toxicants, or both. We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in meta-analyses.

MAIN RESULTS

We included 78 completed studies, representing 22,052 participants, of which 40 were RCTs. Seventeen of the 78 included studies were new to this review update. Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 50 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There was high certainty that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (RR 1.63, 95% CI 1.30 to 2.04; I2 = 10%; 6 studies, 2378 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6). There was moderate-certainty evidence (limited by imprecision) that the rate of occurrence of AEs was similar between groups (RR 1.02, 95% CI 0.88 to 1.19; I2 = 0%; 4 studies, 1702 participants). SAEs were rare, but there was insufficient evidence to determine whether rates differed between groups due to very serious imprecision (RR 1.12, 95% CI 0.82 to 1.52; I2 = 34%; 5 studies, 2411 participants). There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.94, 95% CI 1.21 to 3.13; I2 = 0%; 5 studies, 1447 participants). In absolute terms, this might lead to an additional seven quitters per 100 (95% CI 2 to 16). There was moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 1840 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 8 studies, 1272 participants). Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.66, 95% CI 1.52 to 4.65; I2 = 0%; 7 studies, 3126 participants). In absolute terms, this represents an additional two quitters per 100 (95% CI 1 to 3). However, this finding was of very low certainty, due to issues with imprecision and risk of bias. There was some evidence that (non-serious) AEs were more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low certainty; 4 studies, 765 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 1.03, 95% CI 0.54 to 1.97; I2 = 38%; 9 studies, 1993 participants).  Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons, hence evidence for these is limited, with CIs often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the effect size. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but longest follow-up was two years and the number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates, but further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Electronic Cigarettes for Smoking Cessation: The Gap Between Behavior in Smokers and Medical Education

INTRODUCTION

E-cigarettes have engendered a great deal of controversy within the public health and medical communities.  Methods: Two cross-sectional surveys were administered. First, patients at an annual lung cancer screening appointment who self-identified as former smokers were asked about strategies for achieving and maintaining smoking cessation with open-ended questions. Second, medical students at a single university reported their opinion and knowledge of combustible cigarettes and e-cigarettes.

RESULTS

Among the n=102 in the patient survey indicating that they used e-cigarettes or over-the-counter (OTC) nicotine replacement products for smoking cessation, 34.3% (35/102) vaped e-cigarettes, making it the second most common next to patches (47.1% {48/102}). By comparison, n=48 reported using medication. Medical student participants (n=168) were mixed regarding whether a patient should switch from traditional to electronic cigarettes (56.0% yes; 44.0% no) and reported receiving education about traditional cigarettes (92.3%) at a much higher rate than for e-cigarettes (46.4%), p<.001.

CONCLUSION

Many former heavy smokers undergoing a lung cancer screen used e-cigarettes to achieve smoking cessation. However, nearly half of medical students surveyed do not think patients should switch from traditional to e-cigarettes.

Association of Vaping and Respiratory Health among Youth in the Population Assessment of Tobacco and Health (PATH) Study Wave 3

The purpose of this study is to evaluate the association of electronic nicotine product (ENP) use and its respiratory manifestations in a nationally representative sample of adolescents in the US. Cross-sectional evidence from 9750 adolescents in wave 3 (October 2015-October 2016) of the Population Assessment of Tobacco and Health (PATH) survey was used. Adjusting for demographics, lifetime number of cigarettes and cigars used, home rules about tobacco use, and tobacco used by other household members, we used logistic regression models to examine associations between ENP use and its respiratory manifestations in the past year. Among 9750 adolescents, 12% (n = 1105) used ENP in the past year. Compared to non-users, past-year ENP-users had 37% higher odds of wheezing in general (Adjusted Odds Ratio (AOR) = 1.37, 95% Confidence interval (CI): 1.11-1.71, p = 0.005) and higher odds of wheezing 4-12 times or >12 times per year versus no wheezing (AOR = 1.57, 95% CI: 1.01-2.46, p = 0.05 and AOR = 2.58, 95% CI: 1.04-6.41, p = 0.04, respectively). Additionally, odds of dry cough at night were 23% higher among ENP-users than among non-users (AOR = 1.23, 95% CI: 1.04-1.46, p = 0.02). There was no association between past-year ENP use and exercise-induced wheezing or asthma diagnosis. Among those with asthma, there was no evidence of an association between ENP use and long-acting inhaler or quick-relief inhaler use. ENP use among adolescents is associated with increased frequency of wheezing and dry cough. Early recognition of pulmonary clinical manifestations among young ENP users should be critical considerations in regulatory and prevention efforts to protect public health, and clinical efforts to prevent progression to serious pulmonary complications.

Electronic Cigarettes and Asthma: What Do We Know So Far?

Electronic cigarettes (EC) are a novel product, marketed as an alternative to tobacco cigarette. Its effects on human health have not been investigated widely yet, especially in specific populations such as patients with asthma. With this review, we use the existing literature in order to answer four crucial questions concerning: (1) ECs' role in the pathogenesis of asthma; (2) ECs' effects on lung function and airway inflammation in patients with asthma; (3) ECs' effects on asthma clinical characteristics in asthmatics who use it regularly; and (4) ECs' effectiveness as a smoking cessation tool in these patients. Evidence suggests that many EC compounds might contribute to the pathogenesis of asthma. Lung function seems to deteriorate by the use of EC in this population, while airway inflammation alters, with the aggravation of T-helper-type-2 (Th2) inflammation being the most prominent but not the exclusive effect. EC also seems to worsen asthma symptoms and the rate and severity of exacerbations in asthmatics who are current vapers, whilst evidence suggests that its effectiveness as a smoking cessation tool might be limited. Asthmatic patients should avoid using EC.