Electronic Cigarettes and Fecundability: Results From a Prospective Preconception Cohort Study

Direct health implications of e-cigarette use: a systematic scoping review with evidence assessment

Background

E-cigarettes are often marketed as a less harmful alternative to traditional tobacco cigarettes. Despite their popularity, the evidence regarding their effects on human health remains unclear and is filled with complexities.

Objectives

This systematic review aims to elucidate the direct effects of electronic cigarette use on human health, carefully distinguishing between the specific characteristics of the populations studied.

Methodology

Adhering to the PRISMA guidelines, we conducted a comprehensive search in PubMed/Medline, Web of Science, Scopus, and Google Scholar databases without date restrictions, including articles in both Spanish and English. This approach enabled the identification and analysis of primary studies to understand the direct effect of electronic cigarettes on human health.

Results

A total of 33 studies were included that evaluated cardiovascular, pulmonary, renal, weight and fertility effects. Only five studies analyzed e-cigarettes in healthy populations and seven studies compared healthy individuals against smokers. The effects evaluated on smokers or former tobacco smokers were apparently positive, however, among healthy individuals, increased heart rate, mean arterial pressure, oxidative stress, alteration of respiratory epithelial cells and increased airflow resistance were found.

Conclusion

Smokers or former smokers who switch to e-cigarettes may reduce their exposure to carcinogens and lower their risk of developing severe health issues associated with conventional smoking. However, in healthy individuals who have never smoked traditional cigarettes, the use of e-cigarettes introduces several cardiovascular and respiratory adverse effects. These findings suggest that while e-cigarettes can be a strategic harm reduction tool for smokers, they are not a safe option for non-smokers.

The effects of inhaled pollutants on reproduction in marginalized communities: a contemporary review

Important differences in health that are closely linked with social disadvantage exist within and between countries. According to the World Health Organization, life expectancy and good health continue to increase in many parts of the world, but fail to improve in other parts of the world, indicating that differences in life expectancy and health arise due to the circumstances in which people grow, live, work, and age, and the systems put in place to deal with illness. Marginalized communities experience higher rates of certain diseases and more deaths compared to the general population, indicating a profound disparity in health status. Although several factors place marginalized communities at high risk for poor health outcomes, one important factor is exposure to air pollutants. Marginalized communities and minorities are exposed to higher levels of air pollutants than the majority population. Interestingly, a link exists between air pollutant exposure and adverse reproductive outcomes, suggesting that marginalized communities may have increased reproductive disorders due to increased exposure to air pollutants compared to the general population. This review summarizes different studies showing that marginalized communities have higher exposure to air pollutants, the types of air pollutants present in our environment, and the associations between air pollution and adverse reproductive outcomes, focusing on marginalized communities.

Tobacco or marijuana use and infertility: a committee opinion

In the United States, approximately 21% of adults report some form of tobacco use, although 18% report marijuana use. Although the negative impact of tobacco use in pregnancy is well documented, the impact of tobacco and marijuana on fertility and reproduction is less clear. This committee opinion reviews the potential deleterious effects of tobacco, nicotine, and marijuana use on conception, ovarian follicular dynamics, sperm parameters, gamete mutations, early pregnancy, and assisted reproductive technology outcomes. It also reviews the current status of tobacco smoking cessation strategies. This document replaces the 2018 American Society for Reproductive Medicine Practice Committee document entitled Smoking and Infertility: a committee opinion (Fertil Steril 2018).

"We adjusted for race": now what? A systematic review of utilization and reporting of race in American Journal of Epidemiology and Epidemiology, 2020-2021

Race is a social construct, commonly used in epidemiologic research to adjust for confounding. However, adjustment of race may mask racial disparities, thereby perpetuating structural racism. We conducted a systematic review of articles published in Epidemiology and American Journal of Epidemiology between 2020 and 2021 to (1) understand how race, ethnicity, and similar social constructs were operationalized, used, and reported; and (2) characterize good and poor practices of utilization and reporting of race data on the basis of the extent to which they reveal or mask systemic racism. Original research articles were considered for full review and data extraction if race data were used in the study analysis. We extracted how race was categorized, used-as a descriptor, confounder, or for effect measure modification (EMM)-and reported if the authors discussed racial disparities and systemic bias-related mechanisms responsible for perpetuating the disparities. Of the 561 articles, 299 had race data available and 192 (34.2%) used race data in analyses. Among the 160 US-based studies, 81 different racial categorizations were used. Race was most often used as a confounder (52%), followed by effect measure modifier (33%), and descriptive variable (12%). Fewer than 1 in 4 articles (22.9%) exhibited good practices (EMM along with discussing disparities and mechanisms), 63.5% of the articles exhibited poor practices (confounding only or not discussing mechanisms), and 13.5% were considered neither poor nor good practices. We discuss implications and provide 13 recommendations for operationalization, utilization, and reporting of race in epidemiologic and public health research.

Metabolic and Other Endocrine Elements with Regard to Lifestyle Choices: Focus on E-Cigarettes

Our objective was to overview recent data on metabolic/endocrine disorders with respect to e-cigarette (e-cig) use. This is a narrative review; we researched English, full-length, original articles on PubMed (between January 2020 and August 2023) by using different keywords in the area of metabolic/endocrine issues. We only included original clinical studies (n = 22) and excluded case reports and experimental studies. 3 studies (N1 = 22,385; N2 = 600,046; N3 = 5101) addressed prediabetes risk; N1 showed a 1.57-fold increased risk of dual vs. never smokers, a higher risk that was not confirmed in N2 (based on self-reported assessments). Current non-smokers (N1) who were dual smokers still have an increased odd of prediabetes (a 1.27-fold risk increase). N3 and another 2 studies addressed type 2 diabetes mellitus (DM): a lower prevalence of DM among dual users (3.3%) vs. cigarette smoking (5.9%) was identified. 6 studies investigated obesity profile (4 of them found positive correlations with e-cig use). One study (N4 = 373,781) showed that e-cig use was associated with obesity in the general population (OR = 1.6, 95%CI: 1.3-2.1, p < 0.05); another (N5 = 7505, 0.82% were e-cig-only) showed that obesity had a higher prevalence in dual smokers (51%) vs. cig-only (41.2%, p < 0.05), while another (N6 = 3055) found that female (not male) e-cig smokers had higher body mass index vs. non-smokers. Data on metabolic syndrome (MS) are provided for dual smokers (n = 2): one case-control study found that female dual smokers had higher odds of MS than non-smokers. The need for awareness with respect to potential e-cig--associated medical issues should be part of modern medicine, including daily anamnesis. Whether the metabolic/endocrine frame is part of the general picture is yet to be determined. Surveillance protocols should help clinicians to easily access the medical background of one subject, including this specific matter of e-cig with/without conventional cigarettes smoking and other habits/lifestyle elements, especially when taking into consideration metabolism anomalies.

[Electronic cigarettes and fertility: True or false friends?]

While electronic cigarettes have been on the rise in France for the past ten years, data on their prevalence, use patterns and safety have remained fragmented and controversial. Electronic cigarettes seem to not be a harmless product to use, because although they contain fewer harmful substances than traditional cigarettes, they still contain toxic products such as endocrine disruptors, which appear to have a negative impact on hormonal homeostasis, morphology and functioning of the animal reproductive system. Mostly presented as a harmless alternative to traditional cigarettes by industry lobbies, electronic cigarettes are often offered as an aid to smoking cessation in the same way as nicotinic substitutes. This strategy is especially proposed without knowledge of its effects on human reproductive health. Indeed, there are currently very few scientific publications, which study the impact of the use of electronic cigarettes, nicotine and the vapours it delivers on fertility and the functioning of the human female and male reproductive systems. Thus, the great majority of the data we have to date come from studies carried out in animal populations and show that electronic cigarettes exposure affect fertility. There is, to our knowledge, no scientific publication on the results in Assisted Reproductive Technology in case of use of electronic cigarettes, motivating the realization of the study IVF-VAP currently underway in the department of Medicine and Biology of Reproduction of the Amiens Picardie University Hospital.

Maternal electronic cigarette use during pregnancy affects long-term arterial function in offspring

Vaping, or electronic cigarette (ecig) use, is prevalent among pregnant women, although little is known about the effects of perinatal ecig use on cardiovascular health of the progeny (even when using nicotine-free e-liquid). Maternal toxicant inhalation may adversely affect vital conduit vessel development. We tested the hypothesis that perinatal exposure to maternal vaping would lead to a dose-dependent dysfunction that would persist into later life of offspring. Pregnant Sprague-Dawley rats were exposed to either nicotine-free (ecig0) or nicotine-containing ecig aerosol (18 mg/mL, ecig18) starting on gestational day 2 and continued until pups were weaned (postnatal day 21). Pups were never directly exposed. Conduit artery function (stiffness and reactivity) and structure were assessed in 3- and 7-mo-old offspring. At 3 mo, pulse wave velocity (PWV) in the ecig0 and ecig18 offspring was significantly higher than controls in both the 20 puffs/day (6.6 ± 2.1 and 4.8 ± 1.3 vs. 3.2 ± 0.7 m/s, respectively, P < 0.05, means ± SD) and in 60 puffs/day exposure cohort (7.5 ± 2.8 and 7.5 ± 2.5 vs. 3.2 ± 0.5 m/s, respectively, P < 0.01). Wire myography revealed (range of 23%-31%) impaired aortic relaxation in all ecig exposure groups (with or without nicotine). Incubation of vessels with TEMPOL or Febuxostat reversed the aortic dysfunction, implicating the involvement of reactive oxygen species. Nearly identical changes and pattern was seen in vascular outcomes of 7-mo-old offspring. The take-home message from this preclinical study is that maternal vaping during pregnancy, with or without nicotine, leads to maladaptations in vascular (aortic) development that persist into adult life of offspring.NEW & NOTEWORTHY We observe a significant alteration in arterial structure and function in adolescent and adult offspring due to developmental exposure to toxicants resulting from perinatal maternal vaping. Taken together with previous work that described lasting dysfunction in cerebral microvasculature in offspring, these data underscore the adverse consequences of maternal exposure to electronic cigarette aerosol in conduit and resistance vessels alike, irrespective of nicotine content.

The Health Effects of Real-World Dual Use of Electronic and Conventional Cigarettes versus the Health Effects of Exclusive Smoking of Conventional Cigarettes: A Systematic Review

BACKGROUND

A high prevalence of dual use of e-cigarettes and conventional cigarettes has been reported across the world.

METHODS

A systematic search was carried out. We included original articles on any topic relevant to health, excluding mental health, in all languages. The PRISMA guidelines were followed. Both reviewers independently screened and read all publications. We compared dual use with exclusive smoking of conventional cigarettes (ESCC).

RESULTS

Fifty-two publications (49 studies) were included. Thirteen papers/10 studies were prospective. There was great heterogeneity across studies. Many methodological weaknesses, such as inaccurate exposure measurement, lack of adjustment for former tobacco consumption, and lack of significance testing were identified. Most prospective studies found dual use to be at least as harmful as ESCC. The longest follow-up was six years. Most of the best available cross-sectional studies found dual use associated with the same and, in several studies, significantly higher risk of self-reported symptoms/disease than in ESCC. The intensity of cigarette smoking seems associated with worse health.

CONCLUSION

Existing studies indicate that dual use is at least as, or probably even more, harmful than ESCC. Due to the predominance of cross-sectional studies and the methodological weaknesses we judged the overall certainty of the evidence as "low certainty".

The current situation and future directions for the study on time-to-pregnancy: a scoping review

Introduction

As problems associated with infertility and population aging increase, there is a growing interest in the factors that cause a decline in human fertility. Time-to-pregnancy (TTP) is a good indicator with which to reflect human fecundability. Here, we present a comprehensive overview of this topic.

Methods

Relevant qualitative and quantitative studies were identified by searching the Web of science and PubMed electronic databases. We included all literature, written in English, from inception to the 10th April 2021 providing the focus was on TTP. We conducted a narrative synthesis using thematic analysis.

Results

Traditional TTP-related study protocols include prospective and retrospective cohorts that provide a wealth of data to reveal potential influences on TTP. Thus far, a variety of factors have been shown to be associated with TTP in couples preparing for pregnancy, including basic demographic characteristics, menstrual status, chronic disease status, environmental endocrine disruptor exposure, and lifestyles. However, there are inevitable epidemiological bias in the existing studies, including recall bias, selection bias and measurement bias. Some methodological advances have brought new opportunities to TTP research, which make it possible to develop precision interventions for population fertility. Future TTP studies should take advantage of artificial intelligence, machine learning, and high-throughput sequencing technologies, and apply medical big data to fully consider and avoid possible bias in the design.

Conclusion

There are many opportunities and future challenges for TTP related studies which would provide a scientific basis for the “precise health management” of the population preparing for pregnancy.

As the problems of infertility and population aging increase, there is a growing interest in the factors that cause a decline in human fertility. Time-to-pregnancy (TTP) is a good indicator with which to reflect human fecundability, and a longer TTP is known to reflect a reduction in fertility. Many original studies, with different designs, have used TTP to explore the factors that might influence fertility, including basic demographic characteristics, chronic disease status, environmental endocrine disruptor exposure, and lifestyles. However, much of the existing evidence is inconsistent and limited by various types of bias. This review provides a synopsis of recent TTP studies, and highlights new opportunities and future challenges.

Invited Commentary: The Epidemiology of Electronic Cigarettes and Reproductive Health Begins

Harlow et al. (Am J Epidemiol. 2021;190(3):353-361) are among the first to tackle the complex subject of electronic cigarette use and reproductive health, focused on fecundity but pertinent to the full spectrum of reproductive health concerns. Despite extensive documentation of the health harm from tobacco use and a shared exposure to nicotine, electronic cigarette (e-cigarette) users have a markedly different exposure profile. Because e-cigarettes might help to curtail or eliminate tobacco smoking, the health comparisons of interest for e-cigarettes should include cigarette smoking as well as no use of such products. These researchers confront significant methodological challenges in the study of reproductive health effects of e-cigarettes: addressing confounding with little information on the characteristics of e-cigarette users, a complex connection between e-cigarette and tobacco use, multiple and poorly understood exposure to e-cigarette vapors, and lack of a standard method for quantifying exposure. Evidence is urgently needed to inform regulation and individual decisions regarding the use of this potentially harmful product that might well entice new users of nicotine, some of whom progress to tobacco use, but that also has the potential to enable otherwise recalcitrant smokers to substitute a less harmful product.