E-cigarette users exhibit lower pulmonary function compared to tobacco smokers and non-smokersAbstract
Introduction: The global rise in electronic cigarette (e-cigarette) use has raised concerns due to limited evidence regarding its impact on respiratory health.
Objective: To evaluate and compare pulmonary function among e-cigarette users, tobacco smokers, and non-smokers aged 18 to 40 years.
Methods: In this cross-sectional study, 45 participants were allocated into three groups: non-smokers (control), tobacco smokers, and e-cigarette users. All participants underwent spirometry testing. Inclusion criteria required a minimum of one year of consistent smoking or vaping. Individuals with less than three months of exposure, bronchodilator use, or inability to perform the test were excluded.
Results: The mean age was 25.47 ± 3.93 years for the control group, 23.2 ± 3.3 years for tobacco smokers, and 21.53 ± 3.27 years for e-cigarette users. Dyspnea and wheezing were more frequently reported by tobacco smokers, while cough and wheezing predominated among e-cigarette users. Spirometric analysis revealed no significant differences in forced vital capacity (FVC) among groups. However, e-cigarette users exhibited significantly lower forced expiratory volume in one second (FEV1) and FEV1/FVC ratio compared to non-smokers, and lower FEV1/FVC compared to tobacco smokers, indicating early signs of airflow obstruction.
Conclusion: Despite similar FVC values, e-cigarette users demonstrated reduced expiratory performance, as evidenced by lower FEV1 and FEV1/FVC ratio. These findings suggest that e-cigarette use may be associated with early functional impairment of pulmonary function, potentially exceeding the impact observed in conventional tobacco smokers.
Keywords:
Spirometry; Smoking; Tobacco use; Tobacco consumption; Electronic nicotine delivery systems
Resumo
Introdução: O aumento global do uso de cigarros eletrônicos gera preocupações devido às evidências limitadas sobre seu impacto na saúde respiratória.
Objetivo: Avaliar e comparar a função pulmonar entre usuários de cigarros eletrônicos, fumantes de tabaco e não fumantes com idades entre 18 e 40 anos.
Métodos: Neste estudo transversal, 45 participantes foram alo-cados em três grupos: não fumantes (controle), fumantes de tabaco e usuários de cigarros eletrônicos. Todos os participantes foram submetidos à espirometria. Os critérios de inclusão exigi-ram um período mínimo de um ano de uso consistente de tabaco ou cigarro eletrônico. Indivíduos com menos de três meses de exposição, uso de broncodilatadores ou incapacidade de realizar o teste foram excluídos.
Resultados: A idade média foi de 25,47 ± 3,93 anos para o grupo controle, 23,2 ± 3,3 anos para fumantes de tabaco e 21,53 ± 3,27 anos para usuários de cigarros eletrônicos. Dispneia e sibilos foram relatados com maior frequência pelos fumantes de tabaco, enquanto tosse e sibilos predominaram entre os usuários de cigarros eletrônicos. A análise espirométrica não revelou diferenças significativas na capacidade vital forçada (CVF) entre os grupos. No entanto, os usuários de cigarros eletrônicos apresentaram valores significativamente menores de volume expiratório forçado no primeiro segundo (VEF1) e da relação VEF/CVF em comparação aos não fumantes, bem como uma relação VEF/CVF menor em compa-ração aos fumantes de tabaco, indicando sinais precoces de obstrução do fluxo aéreo.
Conclusão: Apesar de valores de CVF semelhantes, os usuários de cigarros eletrônicos demonstraram desempenho expiratório reduzido, evidenciado por valores menores de VEF1 e da relação VEF/CVF. Esses achados sugerem que o uso de cigarros eletrônicos pode estar associado a um comprometimento funcional precoce da função pulmonar, po-tencialmente superando o impacto observado em fumantes de tabaco convencional.
Palavras-chave:
Espirometria; Tabagismo; Uso de tabaco; Consumo de tabaco; Sistemas eletrônicos de entrega de nicotina
Introduction
In Brazil, tobacco cigarettes are legally restricted for sale to individuals under the age of eighteen, with sales permitted to adults. However, Szklo and Cavalcante1 reported that approximately 45% of adolescent smokers in Brazil are between 13 and 17 years old and regularly purchase cigarettes without facing significant barriers. Tobacco smoke contains over 7,000 chemical compounds, more than 70 of which are recognized as carcinogenic. Smoking is a major risk factor for the development of chronic diseases.2
Pinto et al.3 demonstrated that, in 2015, smoking was responsible for 156,216 deaths in Brazil, accounting for 12.6% of all annual deaths in the country. Among these, 16% were due to cardiovascular diseases and 13% to stroke. The study also revealed that smokers in Brazil face a cumulative mortality risk from chronic obstructive pulmonary disease (COPD) or lung cancer that is 20 times higher than that of non-smokers.
The past decade has seen a significant increase in the use of electronic cigarettes (e-cigarettes) as a smoking cessation tool.2 However, growing evidence suggests that these devices pose a threat to public health. Currently, e-cigarettes are banned in Brazil, as well as in approximately 30 other countries that have adopted similar measures, prohibiting their manufacture, export, import, and sale.4 Recent reports have associated e-ciga-rette use with a broad spectrum of respiratory complications, including e-cigarette or vaping product use-associated lung injury, a condition characterized by respiratory symptoms and pulmonary injury that may require hospitalization.5,6
Despite these restrictions, the widespread use of e-cigarettes remains evident, representing considerable public health concern. Soneji et al.7 identified the use of e-cigarettes as a significant risk factor for smoking initiation among adolescents and young adults. This is attributed to both behavioral and physiological mechanisms: e-cigarette use mimics smoking-related behaviors such as hand-to-mouth gestures, inhalation, and exhalation of vapor; adolescents and young adults using nicotine-containing e-cigarettes are at risk of developing nicotine dependence; and e-cigarette use may trigger cognitive or behavioral processes that increase the likelihood of initiating tobacco smoking, such as the development of positive expectations toward smoking. Moreover, e-cigarettes have been associated with battery-related explosion and burn injuries, which are uncommon but can require hospital admission in a substantial proportion of cases.8
Evidence also suggests that sensory characteristics, particularly flavourings, influence patterns of e-cigarette adoption and concurrent cigarette use among current smokers, with different flavours producing distinct vaping rates and reductions in smoking.9 Furthermore, no e-cigarette model has been proven to be safe for long term use, highlighting the ongoing controversy regarding the potential benefits of these devices.10 Although e-cigarettes are frequently promoted as a safer alternative to conventional cigarettes, current evidence does not support their characterization as risk-free products, particularly regarding respiratory health.11 Given the uncertainty surrounding the effects of e-cigarettes, we aimed to assess their impact on lung function through spirometry in e-cigarette users, tobacco smokers, and non-smokers, and to compare the results among these groups.
Methods
Participants in this cross-sectional study were volunteers, including e-cigarette users, tobacco cigarette smokers, and non-smokers, recruited through social media platforms. Eligible individuals were adults aged between 18 and 40 years, classified as regular users of either e-cigarettes or tobacco cigarettes, or as non-users. All smokers included in the study had a minimum of one year of continuous use of either tobacco or e-cigarettes.
Exclusion criteria comprised individuals classified as non-smokers who had engaged in any form of smoking for more than three consecutive months at any point in their lives, thereby disqualifying them from the nonsmoker group. Also excluded were individuals using bronchodilators who were unable to abstain from medication prior to spirometry testing, as well as those who were unable to complete the proposed evaluation for any reason.
Participants were selected intentionally by convenience sampling. Sample size was determined through a power analysis based on forced vital capacity (FVC) data from Polosa et al.,12 using an effect size (F) of 1.18, a standard error of 0.05, and a power of 95%. The required sample size was 15 individuals per group.
Data collection followed a structured protocol and commenced only after approval by the Research Ethics Committee of the Faculdades Integradas de Taquara (7.059.143). All participants provided written informed consent prior to participation. Initial contact with volunteers was made via social media. Upon agreeing to participate, everyone was scheduled for evaluation at a convenient date and time. On the scheduled day, participants attended the designated location and signed the informed consent form. The clinical interview lasted approximately 10 minutes and aimed to characterize each participant by collecting information on age, sex, duration of cigarette exposure, and signs or symptoms associated with smoking (Figure 1).
Spirometry procedure
Pulmonary function was assessed using the MIR spirometer (Spirobank II, Roma, Italy; Figure 2). The spirometry test, as described by Lopes,13 is a non-invasive procedure widely used for evaluating lung function due to its high applicability and reproducibility.14,15 During the test, the following parameters were recorded: FVC, forced expiratory volume in one second (FEV1), and the FEV1/FVC ratio.
Before the test, essential information was collected and entered the spirometer for calibration and accurate interpretation of results, including height (measured without shoes), age, sex, body mass, and race. The test was conducted with the participant seated comfortably. The procedure was explained in detail to ensure proper understanding of the technique required for accurate execution (Figure 1). The test began with the correct placement of the mouthpiece and application of a nasal clip. The participant was instructed to breathe normally for a few cycles and then exhale fully. Upon reaching complete exhalation, the participant was guided to inhale deeply to total lung capacity. According to the guidelines of Liou and Kanner,16 up to four attempts were permitted to ensure reliable results, with a rest interval of at least one minute between each attempt to prevent muscular fatigue (Figure 1).
Throughout the procedure, the researcher recorded the parameters on a specific data sheet. The collected information was subsequently organized and analyzed, ensuring strict methodological control in the assessment of participants’ pulmonary function.
Statistical analysis
Data from the clinical interview was analyzed using descriptive statistics, including means and percentages. Spirometry data were presented as means and standard deviations. The normality of all variables was assessed using the Shapiro-Wilk test. Group comparisons were performed using one-way analysis of variance (ANOVA) with post-hoc of Bonferroni. All statistical procedures were conducted using SPSS software (SPSS 20.0 for Windows, SPSS Inc., Chicago, IL, USA).
Results
Between October and November 2024, 45 participants were evaluated and divided into three groups. The control group (non-smokers) had a mean age of 25.47 ± 3.93 years, with a predominance of female participants (n = 11; 73.3%). The tobacco cigarette group had a mean age of 23.2 ± 3.3 years, predominantly male (n = 11; 73.3%). The e-cigarette group had a mean age of 21.53 ± 3.27 years, also with a predominance of male participants (n = 12; 80%).
When asked about perceived health changes after initiating cigarette use, 93.33% (14/15) of participants in the tobacco group and 80% (12/15) in the e-cigarette group reported experiencing negative changes. The most frequently reported symptoms among tobacco users were dyspnea and shortness of breath, while e-cigarette users primarily reported cough and shortness of breath (Table 1).
Spirometric analysis revealed no statistically significant differences in FVC among the groups (F(2) = 0.489; p = 0.617), with non-smokers presenting a mean FVC of 95.06 ± 12.29, tobacco cigarette users 95.80 ± 10.10, and e-cigarette users 99.93 ± 19.51 (Table 2). In contrast, FEV1 differed significantly between groups (F(2) = 6.184; p = 0.004), with post hoc analysis indicating a reduction in the e-cigarette group compared to controls (p = 0.004), but no significant differences between tobacco and e-cigarette users (p = 0.107) or between tobacco users and controls (p = 0.592). The FEV1/FVC ratio also differed significantly across groups (F(2) = 10.625; p < 0.001), with lower values observed in e-cigarette users compared to both the control group (p < 0.001) and tobacco users (p = 0.009), while no difference was found between tobacco users and controls (p = 0.550). E-cigarette users exhibited both a lower FEV1 and a reduced FEV1/FVC ratio compared to the other groups, indicating a more pronounced impairment in expiratory airflow. These findings suggest early functional changes consistent with airflow obstruction, despite preserved or slightly elevated FVC. As illustrated in Figure 3, comparative analyses revealed that e-cigarette users exhibited a significant reduction in pulmonary function when compared to both non-smokers and tobacco cigarette users.
Comparison of spirometric parameters among non-smokers, tobacco cigarette users, and e-cigarette users
Discussion
The results did not show significant differences in pulmonary function variables between the control group and tobacco cigarette users, possibly due to the short duration of smoking exposure. This finding is consistent with previous studies by Bird and Staines-Orozco17 and Sherrill et al.,18 which indicate that adolescent smokers generally do not exhibit respiratory problems due to their brief smoking history. This also aligns with the work of Samet,19 who highlights the dose-response relationship between exposure time, the number of cigarettes consumed over the years, and the risk of developing smok-ing-related diseases.
When asked about perceived health changes after starting cigarette use, 93.33% (14/15) of the tobacco cigarette group and 80% (12/15) of the electronic cigarette group reported noticing negative changes. This suggests a perception of lower risk associated with electronic de-vices,20 which may lead to an underestimation of actual risks, as observed by Moran et al.,21 and consequently influence the decision to quit.22
The main health symptoms reported by tobacco cigarette users were dyspnea and shortness of breath, while electronic cigarette users highlighted coughing and shortness of breath. Previous studies confirm this association between conventional smoking and persistent cough, dyspnea, and asthma.23,24,25 Health risks associated with electronic cigarette use are highlighted by Aokage et al.,26 who describe a clinical case of a young individual presenting severe symptoms after using e-cigarettes. Additional research reveals associations between these devices and shortness of breath, fatigue, nausea, vomiting, and respiratory irritation.27 More recently, reviews on e-cigarette or vaping product use-associated lung injury have highlighted that e-cigarette users may develop a broad spectrum of respiratory manifestations, ranging from mild respiratory symptoms to severe pulmonary injury requiring hospitalization.5,6
Regarding the pulmonary function of participants evaluated in this study, a slight decline was observed among tobacco cigarette users, with mean FVC of 95.80 ± 10.10, FEV1 of 87.13 ± 10.77, and FEV1/FVC of 89.26 ± 11.90. These findings are supported by previous stu-dies,28,29 demonstrating a clear dose-response relationship between tobacco cigarette consumption and FEV1 decline. Furthermore, Bossé et al.29 emphasize that changes in FVC are not initially observed in smokers; however, they found that FEV1 was significantly lower in smokers compared to non-smokers, even among younger individuals.
Smoking causes pulmonary changes, leading to airway obstruction and reduced FEV1.30 Additionally, the prevalence of airway obstruction was directly related to age and the number of pack-years, in agreement with the study by Wasswa-Kintu et al.,31 which also identified an association between reduced FEV1 and increased risk of lung cancer. Gold et al.32 also reported a reduction in the FEV1/FVC ratio, identifying a dose-response relationship between smoking and decreased FEV1/FVC and flow between 25 and 75 percent of level in USA youth aged 10 to 18 who smoked an average of five cigarettes per day. Fu et al.33 emphasized that an FEV1/ FVC ratio below 0.70 is indicative of airflow obstruction. However, in contrast to our results, they observed that ap-proximately 14% of smokers exhibited this condition without a prior diagnosis.
This study demonstrated that changes in pulmonary function were more pronounced in the e-cigarette user group, who presented mean FVC of 99.93 ± 19.51, FEV1 of 75.53 ± 16.24, and FEV1/FVC of 73.8 ± 17.75, when compared to the control group and tobacco cigarette users. Our results diverge from previous studies suggesting the use of e-cigarettes as a smoking cessation tool, as well as the suggestion of low toxicity of these devices and the absence of significant changes in FVC and FEV1 after switching from tobacco to e-cigarettes.2,34,35
An unexpected finding of the present study was the greater reduction in FEV1 and FEV1/FVC observed among e-cigarette users despite the higher proportion of daily users in the tobacco cigarette group. This result should be interpreted with caution. The frequency of use recorded in the present study may not accurately reflect the total inhaled exposure, particularly among e-cigarette users, whose consumption patterns are highly variable and depend on factors such as device characteristics, puff frequency, nicotine concentration, and duration of use. Furthermore, cumulative exposure measures, such as pack-years for tobacco smokers, were not available. Therefore, the observed differences cannot be attributed solely to the frequency of use and may reflect unmeasured differences in exposure profiles between groups.
Although e-cigarette users presented a slightly higher FVC, their FEV1 and FEV1/FVC ratio were significantly lower, suggesting airflow obstruction. This pattern is compatible with early-stage obstructive pulmonary dysfunction, in which air trapping or prolonged expiratory effort may preserve or even increase FVC while FEV1 declines. In spirometry, FVC can be artificially elevated if the subject extends the expiration beyond the necessary duration, a behavior that may occur due to over-instruction or an attempt to “perform well” during the test. Therefore, the present findings are consistent with this phenomenon and reinforce the importance of considering the FEV1/ FVC ratio as a primary functional marker of early obstruction, particularly in young populations with recent exposure to smoking.
Conversely, Walele et al.36 monitored the pulmonary function of e-cigarette users over 24 months, revealing a mild but significant reduction in pulmonary function, with declines of 4.0% in FVC and 5.4% in FEV1. Similarly, the study by Ferrari et al.37 showed that five minutes of exposure to nicotine-free e-cigarettes caused significant reductions in FEV1 and FEF25%, increased airway resistance, and induced inflammation.
Our results indicate a reduction in the FEV1/FVC ratio among e-cigarette users, consistent with the study by AboElNaga,38 who observed similar effects when comparing non-smokers and traditional cigarette smokers. These findings are also aligned with the study by Meo et al.,39 which assessed the impact of e-cigarettes on pulmonary function and exhaled nitric oxide levels in 60 healthy young adult males, divided into a control group and daily e-cigarette users. In contrast, Song et al.40 did not find a reduction in the FEV1/FVC ratio. The interpretation of respiratory effects associated with e-cig-arette use remains challenging because these devices are frequently perceived as safer alternatives to conventional cigarettes. However, recent evidence suggests that lower exposure to combustion products should not be interpreted as the absence of respiratory risk, and pulmonary alterations associated with vaping continue to be reported in both experimental and clinical studies.11
Our findings demonstrated lower FEV1 and FEV1/FVC values among e-cigarette users, a pattern that may be compatible with airflow limitation, characterized by a decline in FEV1 and/or FEV1/FVC < 0.7,41 as well as an increased risk of developing severe respiratory diseases such as chronic obstructive pulmonary disease (COPD) and asthma. COPD is the third leading cause of death in the USA, according to the National Center for Health Statistics.42 Smoking cessation is the primary intervention to reduce the impact of COPD.43 Additionally, smoking is a significant risk factor for asthma, contributing to poorer disease control, increased frequency of exacerbations, pulmonary function decline, and increased mor-tality.44
This study presents some important limitations. First, participants were recruited through convenience sampling, which may have introduced selection bias and limited the generalizability of the findings. Second, the cross-sectional design does not allow causal inferences regarding the relationship between smoking behaviors and pulmonary function. Third, potential confounding variables were not fully controlled, including detailed medical history, smoking intensity, and exposure to environmental pollutants. In addition, the distribution of sex was not homogeneous across groups, which may have influenced the results despite the use of spirometric parameters expressed as percentage of predicted values. Furthermore, detailed information allowing calculation of cumulative tobacco exposure (e.g., pack-years) was not available. Finally, future studies should incorporate longitudinal follow-up and larger, more representative samples to investigate the evolution of pulmonary function over time and to better understand the long-term effects of tobacco and e-cigarette use.
Conclusion
E-cigarette users exhibited a significant reduction in pulmonary function, as indicated by lower values of FEV1 and the FEV1/FVC ratio, compared to both tobacco cigarette users and the control group. Although FVC was slightly higher in this group, this pattern, when considered alongside the reductions in FEV1 and FEV1/FVC, may be compatible with airflow limitation; however, the underlying mechanisms were not directly assessed in the present study.
Acknowledgments
Faculdades Integradas de Taquara.
Data availability statement
Data are available upon reasonable request from the corresponding author.
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Note: FVC = forced vital capacity; FEV1 = forced expiratory volume in one second.
Note: *Indicates significant difference between groups. FVC = forced vital capacity; FEV1 = forced expiratory volume in one second.