Persistent effects of maternal smoking during pregnancy on lung function and asthma in adolescents

Effectiveness of smoking cessation interventions in pregnant women attending primary care: a scoping review

BACKGROUND

Smoking during pregnancy has many adverse effects for infant and mother. Despite this, many pregnant women continue smoking. Primary care is a suitable area to provide smoking cessation interventions.

AIM

To investigate available literature regarding effectiveness of smoking cessation interventions for pregnant women in primary care, the factors contributing to this effectiveness, and to provide suggestions for future research.

DESIGN & SETTING

Systematic scoping literature review.

METHOD

The methodology followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews. Five electronic databases were searched. Inclusion criteria included original research studies and studies published in English. Data were extracted using a modified Joanna Briggs Institute (JBI) data-charting tool.

RESULTS

The initial search yielded 878 articles. Following article screening, 12 studies were included. Five studies found a statistically significant increase in smoking cessation rates or reduction in tobacco consumed in the intervention group. The remaining studies showed no significant difference between the groups. However, 10 studies showed the control group received usual antenatal care involving smoking cessation promotion. An increase in smoking cessation rates was seen in intervention and control groups, demonstrating the effectiveness of these interventions. Interventions included education, counselling, self-help, and financial incentives. They were delivered by GPs, midwives, counsellors, and pregnancy advisers.

CONCLUSION

Primary care is suitable to offer smoking cessation interventions to pregnant women, as it is often the first point of care and more easily accessible than secondary care. Future research is needed to determine the most effective types of interventions.

Factors related with lung functions among Orang Asli in Tasik Chini, Malaysia: a cross-sectional study

BACKGROUND

Orang Asli lifestyle and household setting may influence their health status especially respiratory system and lung functions. This cross-sectional study was carried out to investigate the status of lung functions of Orang Asli community and the associated factors.

METHODS

Data collection was carried out from November 2017 until May 2018 among 211 Orang Asli respondents aged 18 years old and above, who lived in five villages in Tasik Chini, Pahang. All respondents who fulfilled the inclusion criteria were recruited in this study. Interview-guided questionnaire was administered, and spirometry test that include Forced Expiratory Volume in one second (FEV1), Forced Vital Capacity (FVC), and Peak Expiratory Flow Rate (PEFR) was carried out. Data were analyzed using SPSS software version 23.0. In the first stage, descriptive analysis was done to describe the characteristics of the respondents. In the second stage, bivariable analysis was carried out to compare proportions. Finally, multiple logistic regression was performed to assess the effects of various independent predictors on spirometry parameters.

RESULTS

The respondents' age ranged from 18 to 71 years old in which 50.2% of them were female. The majority ethnicity in Tasik Chini was Jakun tribe (94.3%). More than half of the respondents (52.1%) were current smoker, 5.2% were ex-smoker and 41.7% were non-smoker. More than half of them (62.1%) used woodstove for cooking, compared to only 37.9% used cleaner fuel like Liquefied Petroleum Gas (LPG) as a fuel for everyday cooking activity. The lung function parameters (FEV1 and FVC) were lower than the predictive value, whereas the ratio of Forced Expiratory Volume in one second and Forced Vital Capacity (FEV1/FVC) (%) and PEFR were within the predictive value. The FEV1 levels were significantly associated with age group (18-39 years old) (p = 0.002) and presence of woodstove in the house (p = 0.004). FVC levels were significantly associated with presence of woodstove in the house (p = 0.004), whereas there were no significant associations between all factors and FEV1/FVC levels.

CONCLUSIONS

FEV1 levels were significantly associated with age group 18-39 years old, whereas FVC levels were significantly associated with the presence of woodstove in the house. Thus, environmental interventions such as replacing the use of woodstove with LPG, need to be carried out to prevent further worsening of respiratory health among Orang Asli who lived far from health facilities. Moreover, closer health monitoring is crucial especially among the younger and productive age group.

Smoking exposure trajectories and pulmonary function in early adulthood in a Brazilian cohort

OBJECTIVES

To investigate smoking trajectories and their association with pulmonary function (PF) and respiratory symptoms at age 22.

METHODS

Data from a population-based cohort study of 3350 individuals and their spirometries were analysed. The outcomes were: forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), forced expiratory flow at the mid expiratory phase (FEF25-75 %), FEV1/FVC and FEF25-75/FVC ratio. Smoking data were collected at perinatal follow-up (gestational exposure) and 15, 18 and 22 years. Group-based trajectory model was applied.

RESULTS

Four groups were identified: no exposure (NE), gestational (GE), gestational and adulthood (GAE) and continuous (CE) exposure. Both CE and GAE trajectories were associated with lower values of FEV1/FVC (-1.77pp; p = 0.01 and -1.58 pp; p<0.001 respectively) and FEF25-75/FVC ratio (-7.27pp; p = 0.019 and -6.04pp; p<0.001 respectively) compared to the NE trajectory. Lower FEV1 and FEF25-75 % values were also related to the GAE trajectory (-68 ml; p = 0.03 and -253 ml/s;p<0.001 respectively). Compared to those who never smoked, individuals who smoked 10 or more cigarettes daily presented a reduction in the FEV1/FVC ratio by 1.37pp (p<0.001), FEF25-75 % by 126 ml (p = 0.012) and FEF25-75 %/FVC ratio by 3.62pp (p = 0.011). CE trajectory showed higher odds of wheezing (OR 4.14; p<0.001) and cough (OR 2.39; p = 0.002) compared to the non-exposed group.

CONCLUSIONS

The in-uterus exposure to maternal smoking reduces PF later in life. However, the perpetuation of smoking behaviour throughout adolescence and early adulthood is determinant for PF main reduction and the emergence of respiratory-related symptoms.

Airway epithelial development and function: A key player in asthma pathogenesis?

Though asthma is a common and relatively easy to diagnose disease, attempts at primary or secondary prevention, and cure, have been disappointing. The widespread use of inhaled steroids has dramatically improved asthma control but has offered nothing in terms of altering long-term outcomes or reversing airway remodeling and impairment in lung function. The inability to cure asthma is unsurprising given our limited understanding of the factors that contribute to disease initiation and persistence. New data have focused on the airway epithelium as a potentially key factor orchestrating the different stages of asthma. In this review we summarize for the clinician the current evidence on the central role of the airway epithelium in asthma pathogenesis and the factors that may alter epithelial integrity and functionality.

Risk Factors Affecting Development and Persistence of Preschool Wheezing: Consensus Document of the Emilia-Romagna Asthma (ERA) Study Group

Wheezing at preschool age (i.e., before the age of six) is common, occurring in about 30% of children before the age of three. In terms of health care burden, preschool children with wheeze show double the rate of access to the emergency department and five times the rate of hospital admissions compared with school-age asthmatics. The consensus document aims to analyse the underlying mechanisms involved in the pathogenesis of preschool wheezing and define the risk factors (i.e., allergy, atopy, infection, bronchiolitis, genetics, indoor and outdoor pollution, tobacco smoke exposure, obesity, prematurity) and the protective factors (i.e., probiotics, breastfeeding, vitamin D, influenza vaccination, non-specific immunomodulators) associated with the development of the disease in the young child. A multidisciplinary panel of experts from the Emilia-Romagna Region, Italy, addressed twelve key questions regarding managing preschool wheezing. Clinical questions have been formulated by the expert panel using the PICO format (Patients, Intervention, Comparison, Outcomes). Systematic reviews have been conducted on PubMed to answer these specific questions and formulate recommendations. The GRADE approach has been used for each selected paper to assess the quality of the evidence and the degree of recommendations. Based on a panel of experts and extensive updated literature, this consensus document provides insight into the pathogenesis, risk and protective factors associated with the development and persistence of preschool wheezing. Undoubtedly, more research is needed to improve our understanding of the disease and confirm the associations between certain factors and the risk of wheezing in early life. In addition, preventive strategies must be promoted to avoid children's exposure to risk factors that may permanently affect respiratory health.

Effects of life-stage and passive tobacco smoke exposure on pulmonary innate immunity and influenza infection in mice

Limited data are available on the effects of perinatal environmental tobacco smoke (ETS) exposure for early childhood influenza infection. The aim of the present study was to examine whether perinatal versus adult ETS exposure might provoke more severe systemic and pulmonary innate immune responses in mice inoculated with influenza A/Puerto Rico/8/34 virus (IAV) compared to phosphate-buffered saline (PBS). BALB/c mice were exposed to filtered air (FA) or ETS for 6 weeks during the perinatal or adult period of life. Immediately following the final exposure, mice were intranasally inoculated with IAV or PBS. Significant inflammatory effects were observed in bronchoalveolar lavage fluid of neonates inoculated with IAV (FA+IAV or ETS+IAV) compared to PBS (ETS+PBS or FA+PBS), and in the lung parenchyma of neonates administered ETS+IAV versus FA+IAV. Type I and III interferons were also elevated in the spleens of neonates, but not adults with ETS+IAV versus FA+IAV exposure. Both IAV-inoculated neonate groups exhibited significantly more CD4 T cells and increasing numbers of CD8 and CD25 T cells in lungs relative to their adult counterparts. Taken together, these results suggest perinatal ETS exposure induces an exaggerated innate immune response, which may overwhelm protective anti-inflammatory defenses against IAV, and enhances severity of infection at early life stages (e.g., in infants and young children).

In utero exposure to electronic-cigarette aerosols decreases lung fibrillar collagen content, increases Newtonian resistance and induces sex-specific molecular signatures in neonatal mice

Approximately 7% of pregnant women in the United States use electronic-cigarette (e-cig) devices during pregnancy. There is, however, no scientific evidence to support e-cig use as being 'safe' during pregnancy. Little is known about the effects of fetal exposures to e-cig aerosols on lung alveologenesis. In the present study, we tested the hypothesis that in utero exposure to e-cig aerosol impairs lung alveologenesis and pulmonary function in neonates. Pregnant BALB/c mice were exposed 2 h a day for 20 consecutive days during gestation to either filtered air or cinnamon-flavored e-cig aerosol (36 mg/mL of nicotine). Lung tissue was collected in offspring during lung alveologenesis on postnatal day (PND) 5 and PND11. Lung function was measured at PND11. Exposure to e-cig aerosol in utero led to a significant decrease in body weights at birth which was sustained through PND5. At PND5, in utero e-cig exposures dysregulated genes related to Wnt signaling and epigenetic modifications in both females (~ 120 genes) and males (40 genes). These alterations were accompanied by reduced lung fibrillar collagen content at PND5-a time point when collagen content is close to its peak to support alveoli formation. In utero exposure to e-cig aerosol also increased the Newtonian resistance of offspring at PND11, suggesting a narrowing of the conducting airways. At PND11, in females, transcriptomic dysregulation associated with epigenetic alterations was sustained (17 genes), while WNT signaling dysregulation was largely resolved (10 genes). In males, at PND11, the expression of only 4 genes associated with epigenetics was dysregulated, while 16 Wnt related-genes were altered. These data demonstrate that in utero exposures to cinnamon-flavored e-cig aerosols alter lung structure and function and induce sex-specific molecular signatures during lung alveologenesis in neonatal mice. This may reflect epigenetic programming affecting lung disease development later in life.

Association between Asthma Control and Exposure to Greenness and Other Outdoor and Indoor Environmental Factors: A Longitudinal Study on a Cohort of Asthmatic Children

Achieving and maintaining asthma control (AC) is the main goal of asthma management. Indoor and outdoor environmental factors may play an important role on AC. The aim of this longitudinal study was to evaluate the association between AC and exposure to greenness and other outdoor or indoor environmental factors in a cohort of asthmatic children. This study involved 179 asthmatic children (5-16 years). Parents were interviewed through a modified version of the SIDRIA questionnaire. AC was assessed at each visit. Exposure to greenness was measured using the normalized difference vegetation index (NDVI). A logistic regression model was applied for assessing risk factors for uncontrolled asthma (UA). Low NDVI exposure was a risk factor for UA (OR: 2.662, 95% CI (1.043-6.799)); children exposed to passive smoke during pregnancy had a higher risk of UA than those non-exposed to passive smoke during pregnancy (OR: 3.816, 95% CI (1.114-13.064)); and a unit increase in the crowding index was associated with an increased risk of UA (OR: 3.376, 95% CI (1.294-8.808)). In conclusion, the current study provided a comprehensive assessment of urban-related environmental exposures on asthma control in children, using multiple indicators of greenness and other outdoor or indoor environmental factors.

Cigarette Smoke Particle-Induced Lung Injury and Iron Homeostasis

It is proposed that the mechanistic basis for non-neoplastic lung injury with cigarette smoking is a disruption of iron homeostasis in cells after exposure to cigarette smoke particle (CSP). Following the complexation and sequestration of intracellular iron by CSP, the host response (eg, inflammation, mucus production, and fibrosis) attempts to reverse a functional metal deficiency. Clinical manifestations of this response can present as respiratory bronchiolitis, desquamative interstitial pneumonitis, pulmonary Langerhans’ cell histiocytosis, asthma, pulmonary hypertension, chronic bronchitis, and pulmonary fibrosis. If the response is unsuccessful, the functional deficiency of iron progresses to irreversible cell death evident in emphysema and bronchiectasis. The subsequent clinical and pathological presentation is a continuum of lung injuries, which overlap and coexist with one another. Designating these non-neoplastic lung injuries after smoking as distinct disease processes fails to recognize shared relationships to each other and ultimately to CSP, as well as the common mechanistic pathway (ie, disruption of iron homeostasis).

Nicotine replacement therapy and e-cigarettes in pregnancy and infant respiratory outcomes

BACKGROUND

Nicotine replacement therapy (NRT) and e-cigarettes are recommended to pregnant women who wish to stop smoking. Albeit eliminating other harmful components of cigarettes, those alternatives still expose the developing fetus to nicotine. The lungs may be particularly vulnerable to damage by nicotine as there is widespread nicotinic-acetylcholine receptor expression in the lungs. There is, however, a paucity of information about the effect of NRT and e-cigarette use in pregnancy on infant respiratory outcomes.

AIMS

To explore the effect of NRT and e-cigarettes on the developing lung.

STUDY DESIGN

A literature search was undertaken to examine the use and safety of nicotine-replacement strategies in pregnancy, with a focus on infant respiratory outcomes. This included experimental studies investigating the effect of isolated "gestational" nicotine on the developing lung.

OUTCOME MEASURES

Respiratory outcomes in animal studies and infants.

RESULTS

Animal studies investigating the effect of gestational nicotine exposure on fetal lung development demonstrated abnormal lung growth; including abnormal airway branching and alveolar development. Consequently, offspring display altered pulmonary mechanics, including both increased respiratory rate and airway resistance. These findings mirror respiratory pathology observed in infants born to smoking mothers. Human trials of NRT and e-cigarette use in pregnancy have not identified adverse perinatal outcomes regarding reduced birthweight or prematurity, but have not considered infant and childhood respiratory outcomes.

CONCLUSIONS

Nicotine can impair fetal lung development, leading to concerns regarding the safety of NRT and e-cigarettes in pregnancy. Studies have yet to explore the impact of these nicotine-containing products on infant respiratory outcomes.

Effective Ways to Prevent Allergic Diseases: Where Do We Stand?

Since allergic diseases are of great public health relevance, effective primary prevention strategies are urgently needed. This chapter gives an overview of existing primary prevention programs on environmental exposures and dietary strategies based on epidemiological studies which have defined risk- and protective factors for the development of allergic diseases.The allergy protective effect mediated by growing up on a traditional farm environment is well studied. But the exact underlying mechanisms have still not been fully clarified and have not yet led to concrete prevention strategies. The beneficial effect of avoiding cigarette smoke exposure, indoor moisture and molds in pregnancy and childhood on the development of asthma is well documented. Whereas the avoidance of house dust mite exposure is not recommended to prevent eczema or allergy. Dietary supplementation with vitamins, pre- and probiotics in pregnant woman and their offspring is not harmful but evidence for the prevention of allergic diseases is still lacking. Fish oil consumption was shown to be asthma protective. The early introduction of peanuts and egg protein to prevent peanut and egg allergy in children with atopic dermatitis is promising. Further studies are needed to increase the overall evidence in allergy prevention. Most studies lack methodological standards such as randomization and blinding. More evidence is in demand on the potential beneficial impact of multifaceted interventional studies. The future of allergy prevention strategies might be based on individual risk assessment. Therefore, research in the immunological and molecular basis of allergic diseases needs to be promoted.

Microecology research: a new target for the prevention of asthma

The incidence and prevalence of asthma have increased remarkably in recent years. There are lots of factors contributing to the occurrence and development of asthma. With the improvement of sequencing technology, it has been found that the microbiome plays an important role in the formation of asthma in early life. The roles of the microbial environment and human microbiome in the occurrence and development of asthma have attracted more and more attention. The environmental microbiome influences the occurrence of asthma by shaping the human microbiome. The specific mechanism may be related to the immune regulation of Toll-like receptors and T cells (special Tregs). Intestinal microbiome is formed and changed by regulating diet and lifestyle in early life, which may affect the development and maturation of the pulmonary immune system through the intestinal-pulmonary axis. It is well-recognized that both environmental microbiomes and human microbiomes can influence the onset of asthma. This review aims to summarize the recent advances in the research of microbiome, its relationship with asthma, and the possible mechanism of the microbiome in the occurrence and development of asthma. The research of the microbial environment and human microbiome may provide a new target for the prevention of asthma in children who have high-risk factors to allergy. However, further study of “when and how” to regulate microbiome is still needed.

Tobacco Smoking and Risk for Pulmonary Fibrosis: A Prospective Cohort Study From the UK Biobank

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease of unknown origin. A limited number of small studies show an effect of tobacco smoking on risk of IPF, but second-hand smoking has not been examined.

RESEARCH QUESTION

Are smoking-related exposures associated with risk of IPF and does interaction between them exist?

STUDY DESIGN AND METHODS

We designed a prospective cohort study using UK Biobank data, including 437,453 nonrelated men and women of White ethnic background (40-69 years of age at baseline). We assessed the effect of tobacco smoking-related exposures on risk for IPF using Cox regression adjusted for age, sex, Townsend deprivation index, and home area population density. We also examined potential additive and multiplicative interaction between these exposures. Multiple imputation with chained equations was used to address missing data.

RESULTS

We identified 802 incident IPF cases. We showed an association between smoking status (hazard ratio [HR], 2.12; 95% CI, 1.81-2.47), and maternal smoking (HR, 1.38; 95% CI, 1.18-1.62) with risk of IPF. In ever smokers, a dose-response relationship was observed between pack-years of smoking and risk of IPF (HR per 1-pack-year increase, 1.013; 95% CI, 1.009-1.016). Furthermore, an additive and multiplicative interaction was observed between maternal smoking and smoking status, with a relative excess risk due to interaction of 1.00 (95% CI, 0.45-1.54) and a ratio of HRs of 1.50 (95% CI, 1.05-2.14).

INTERPRETATION

Active and maternal tobacco smoking have an independent detrimental effect on risk of IPF and work synergistically. Also, intensity of smoking presents a dose-response association with IPF, strengthening the hypothesis for a potentially causal association.

Factors and mechanisms contributing to the development of preschool wheezing disorders

INTRODUCTION

Half of all children will experience an episode of wheezing by their sixth birthday and acute episodes of wheezing in preschool children account for the majority of all childhood hospital admissions for wheeze. Recurrent preschool wheezing associates with early loss of lung function and a life-long impact on lung health.

AREAS COVERED

We reviewed the literature on PubMed from August 2010-2020 focussing on factors associated with wheeze inception and persistence, paying specific attention to mechanistic studies that have investigated the impact of early life exposures in shaping immune responses in children with underlying susceptibility to wheezing. In particular, the role of early allergen sensitization, respiratory infections, and the impact of the environment on shaping the airway microbiome and resulting immune responses are discussed.

EXPERT OPINION

There is an abundance of associative data showing the role of in utero and postnatal factors influencing wheeze onset and persistence. However, mechanistic and stratified, biomarker-based interventional studies that confirm these associations are now needed if we are to impact the significant healthcare burden resulting from preschool wheezing disorders.

Women's Cigarette and Marijuana Use in Pregnancy: Identifying the Role of Past Versus Recent Violence Exposure

Both cigarette smoking and marijuana use during pregnancy pose serious risks to healthy fetal development, yet little is known about the comparative contribution of recent versus past traumatic experiences to women's smoking behavior. The current study aimed to examine the relative contributions of childhood adversity and past year intimate partner violence (IPV) to women's cigarette and marijuana use during pregnancy in a high-risk, low-income sample. Participants (n = 101) were interviewed to evaluate past year IPV, childhood adversity, and cigarette and marijuana use. Results indicated that approximately one in four pregnant women in the sample reported that they were currently smoking cigarettes. Only a minority of those who reported prepregnancy smoking (22.5%) were able to quit smoking once pregnant. Regarding marijuana use, 6.9% of women reported use during pregnancy, with 68.1% of women using prior to pregnancy ceasing use once pregnant. Results of multinomial regressions controlling for income and education indicated that past year physical abuse by a partner was associated with light cigarette use during pregnancy whereas high rates of childhood adversity were associated with moderate cigarette use during pregnancy. Sexual IPV was associated with marijuana use during pregnancy. Comprehensive assessment of women's history of exposure to violence, including both past and recent exposure, provides insight into which women may have the most difficulty with unassisted cessation in the prenatal period. Providing better intervention and support around cigarette and marijuana cessation for women exposed to violence is a critical need, especially among groups that are at sociodemographic risk for substance use in pregnancy.

Sex dependent effect of maternal e-nicotine on F1 Drosophila development and airways

E-cigarettes are heavily advertised as healthier alternative to common tobacco cigarettes, leading more and more women to switch from regular cigarettes to ENDS (electronic nicotine delivery system) during pregnancy. While the noxious consequences of tobacco smoking during pregnancy on the offspring health are well-described, information on the long-term consequences due to maternal use of e-cigarettes do not exist so far. Therefore, we aimed to investigate how maternal e-nicotine influences offspring development from earliest life until adulthood. To this end, virgin female Drosophila melanogaster flies were exposed to nicotine vapor (8 µg nicotine) once per hour for a total of eight times. Following the last exposure, e-nicotine or sham exposed females were mated with non-exposed males. The F1-generation was then analyzed for viability, growth and airway structure. We demonstrate that maternal exposure to e-nicotine not only leads to reduced maternal fertility, but also negatively affects size and weight, as well as tracheal development of the F1-generation, lasting from embryonic stage until adulthood. These results not only underline the need for studies investigating the effects of maternal vaping on offspring health, but also propose our established model for analyzing molecular mechanisms and signaling pathways mediating these intergenerational changes.

Prenatal Nicotine Exposure Induces Low Birthweight and Hyperinsulinemia in Male Rats

Smoking during pregnancy is one of the causes of low birthweight. Ingestion of nicotine during pregnancy has various metabolic impacts on the fetus and offspring. According to the developmental origins of health and disease theory, low birthweight is a risk factor for developing various non-communicable diseases, including diabetes. We hypothesized that when nicotine-induced low-birthweight rats, when exposed to a high-fat diet (HFD) after growth, are predisposed to glucose intolerance as a result of a mismatch between the eutrophic environment and small body size. Therefore, we investigated whether hyperinsulinemia was caused by exposure of nicotine-induced low-birthweight rats to HFD, including whether this phenomenon exhibited possible sex differences. The average birthweight and body weight at weaning day of offspring from nicotine-administered dams was lower than those of controls. The offspring from nicotine-administered dams did not show rapid fat accumulation after exposure to HFD, and weight and body fat ratio of these animals did not differ from those of the controls. Blood glucose levels did not differ between the groups, but insulin levels increased only in male HFD-exposed offspring from nicotine-administered dams. Similarly, only in HFD-exposed male from nicotine-administered dams showed decreases in the insulin receptor expression in the liver. We conclude that male rats subjected to prenatal nicotine exposure develop hyperinsulinemia when exposed to HFD after growth. Our results suggest that decreased expression of insulin receptors in the liver may be involved in the mechanism underlying hyperinsulinemia in low-birthweight offspring, a phenomenon that appeared to exhibit a sex-specific bias.

Co-methylation analysis in lung tissue identifies pathways for fetal origins of COPD

COPD likely has developmental origins; however, the underlying molecular mechanisms are not fully identified. Investigation of lung tissue-specific epigenetic modifications such as DNA methylation using network approaches might facilitate insights linking in utero smoke (IUS) exposure and risk for COPD in adulthood.We performed genome-wide methylation profiling for adult lung DNA from 160 surgical samples and 78 fetal lung DNA samples isolated from discarded tissue at 8-18 weeks of gestation. Co-methylation networks were constructed to identify preserved modules that shared methylation patterns in fetal and adult lung tissues and associations with fetal IUS exposure, gestational age and COPD.Weighted correlation networks highlighted preserved and co-methylated modules for both fetal and adult lung data associated with fetal IUS exposure, COPD and lower adult lung function. These modules were significantly enriched for genes involved in embryonic organ development and specific inflammation-related pathways, including Hippo, phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT), Wnt, mitogen-activated protein kinase and transforming growth factor-β signalling. Gestational age-associated modules were remarkably preserved for COPD and lung function, and were also annotated to genes enriched for the Wnt and PI3K/AKT pathways.Epigenetic network perturbations in fetal lung tissue exposed to IUS and of early lung development recapitulated in adult lung tissue from ex-smokers with COPD. Overlapping fetal and adult lung tissue network modules highlighted putative disease pathways supportive of exposure-related and age-associated developmental origins of COPD.

Air pollution and family related determinants of asthma onset and persistent wheezing in children: nationwide case-control study

OBJECTIVE

To identify risk factors (air pollution and family related) for the onset of asthma and persistent wheezing in children.

DESIGN

Nationwide case-control study.

SETTING

Denmark.

PARTICIPANTS

All Danish children born from 1997 to 2014 and followed for asthma onset and persistent wheezing from age 1 year to 15 years.

MAIN OUTCOME MEASURE

Onset of asthma and persistent wheezing.

RESULTS

A higher incidence of asthma was found in children of parents with asthma (adjusted hazard ratio 2.29 (95% confidence interval 2.22 to 2.35) and mothers who smoked during pregnancy (1.20, 1.18 to 1.22), whereas a lower incidence was found in children of parents with high educational attainment (0.72, 0.69 to 0.75) and high incomes (0.85, 0.81 to 0.89). Exposure to particulate matter ≤2.5 µm (PM_2.5) and ≤10 µm (PM₁₀) and nitrate was associated with an increased risk of asthma and persistent wheezing, with hazard ratios per 5 µg/m³ increase in pollutant concentrations 1.05 (1.03 to 1.07) for PM_2.5, 1.04 (1.02 to 1.06) for PM₁₀, and 1.04 (1.03 to 1.04) for nitrogen dioxide. Only the positive association of PM_2.5 with asthma and persistent wheezing remained robust across the different models and in sensitivity analyses.

CONCLUSIONS

The findings of this study suggest that children exposed to higher levels of PM_2.5 are more likely to develop asthma and persistent wheezing than children who are not exposed. Other risk factors associated with these outcomes were parental asthma, parental education, and maternal smoking during pregnancy.

The rise of electronic nicotine delivery systems and the emergence of electronic-cigarette-driven disease

In 2019, the United States experienced the emergence of the vaping-associated lung injury (VALI) epidemic. Vaping is now known to result in the development and progression of severe lung disease in the young and healthy. Lack of regulation on electronic cigarettes in the United States has resulted in over 2,000 patients and 68 deaths. We examine the clinical representation of VALI and the delve into the scientific evidence of how deadly exposure to electronic cigarettes can be. E-cigarette vapor is shown to affect numerous cellular processes, cellular metabolism, and cause DNA damage (which has implications for cancer). E-cigarette use is associated with a higher risk of developing crippling lung conditions such as chronic obstructive pulmonary disease (COPD), which would develop several years from now, increasing the already existent smoking-related burden. The role of vaping and virus susceptibility is yet to be determined; however, vaping can increase the virulence and inflammatory potential of several lung pathogens and is also linked to an increased risk of pneumonia. As it has emerged for cigarette smoking, great caution should also be given to vaping in relation to SARS-CoV-2 infection and the COVID-19 pandemic. Sadly, e-cigarettes are continually promoted and perceived as a safer alternative to cigarette smoking. E-cigarettes and their modifiable nature are harmful, as the lungs are not designed for the chronic inhalation of e-cigarette vapor. It is of interest that e-cigarettes have been shown to be of no help with smoking cessation. A true danger lies in vaping, which, if ignored, will lead to disastrous future costs.

[In Utero Exposure to Maternal Smoking: Impact on the Child from Birth to Adulthood - CNGOF-SFT Expert Report and Guidelines for Smoking Management during Pregnancy]

INTRODUCTION

Smoking during pregnancy leads to fetal passive smoking. It is associated with several obstetrical complications and is a major modifiable factor of maternal and fetal morbidity. Long-term consequences also exist but are less well known to health professionals and in the general population.

METHODS

Consultation of the Medline® database.

RESULTS

Maternal smoking during pregnancy is associated in the offspring with sudden infant death syndrome (NP2), impaired lung function (NP2), lower respiratory infections and asthma (NP2), overweight and obesity (NP2), cancers (NP3), risk of tobacco use, nicotine dependence and early smoking initiation (NP2). Unadjusted analyses show associations between in utero tobacco exposure and cognitive deficits (NP3), impaired school performance (NP3) and behavioral disorders in children (NP2), which are in a large part explained by environmental factors. There is a cross-generational effect of smoking during pregnancy. For example, an increased risk of asthma is observed in the grandchildren of smoking women (NP4). The respective roles of ante- and post-natal smoking remain difficult to assess.

CONCLUSION

These results highlight the importance of prevention measures against tobacco use in the general population, as well as screening measures and support for smoking cessation before or at the beginning of the pregnancy.

Maternal smoking during pregnancy affects adult onset of asthma in offspring: a follow up from birth to age 46 years

RATIONALE

Environmental tobacco smoke (ETS) exposure increases asthma risk in children. There is limited knowledge of prenatal ETS for adult-onset asthma.

OBJECTIVES

To determine the association between prenatal ETS and adult onset asthma.

MEASUREMENTS AND MAIN RESULTS

The questionnaire and clinical data of 5200 people, free of physician-diagnosed asthma by 31 years of age, who were included in the Northern Finland Birth Cohort 1966 Study was used. The association of maternal smoking during the last 3 months of pregnancy with onset of physician-diagnosed asthma and with lung function in adult offspring was studied using adjusted multivariate regression analyses. The cumulative incidence of physician-diagnosed asthma between the ages of 31 and 46 years was 5.1% among men and 8.8% among women. Gestational smoke exposure was associated with adult-onset asthma among offspring (adjusted OR 1.54, 95% CI 1.04-2.29), namely among offspring who reported either past non-diagnosed asthma (OR 9.63, 95% CI 2.28-40.67) or past cough with wheeze (3.21, 95% CI 1.71-6.05). A significant association was detected between gestational smoke exposure and the offspring's forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) ratio at 31 years of age. In offspring with the haplotype rs11702779-AA of RUNX1, gestational smoke exposure was associated with adult-onset asthma (5.53, 95% CI 2.11-14.52, adjusted p-value for interaction 0.10).

CONCLUSION

Maternal smoking during pregnancy is associated with the cumulative incidence of asthma in offspring between the ages of 31 and 46 years. The association was accentuated in offspring who at age 31, reported having past respiratory problems and/or who had haplotype rs11702779-AA. A reduction in FEV₁/FVC ratio was also observed at age 31 years in offspring with gestational smoke exposure. These results could reflect the early vulnerability of offspring's airways to ETS and its putative long-term effects.

Associations of α- and γ-tocopherol during early life with lung function in childhood

BACKGROUND

Tocopherol isoforms may regulate child lung growth and spirometric measures.

OBJECTIVE

Our aim was to determine the extent to which plasma α-tocopherol (α-T) or γ-tocopherol (γ-T) isoform levels in early childhood or in utero are associated with childhood lung function.

METHODS

We included 622 participants in the Project Viva cohort who had lung function at a mid-childhood visit (age 6-10 years). Maternal and child tocopherol isoform levels were measured by HPLC at the second trimester and 3 years of age, respectively. Multivariable linear regression models (adjusted for mid-childhood body mass index z scores, maternal education, smoking in pregnancy, and prenatal particulate matter with diameter of <2.5 micrometers (PM_2.5) particulate exposure) stratified by tertiles of child γ-T level were used to assess the association of α-T levels with FEV₁ and forced vital capacity (FVC) percent predicted. Similarly, models stratified by child α-T tertile evaluated associations of γ-T levels with lung function. We performed similar analyses with maternal second trimester tocopherol isoform levels.

RESULTS

The median maternal second trimester α-T level was 63 μM (interquartile range = 47-82). The median early-childhood level was 25 μM (interquartile range = 20-33 μM). In the lowest tertile of early-childhood γ-T, children with a higher α-T level (per 10 μM) had a higher mid-childhood FEV₁ percent predicted (β = 3.09; 95% CI = 0.58-5.59 and a higher FVC percent predicted (β = 2.77; 95% CI = 0.47-5.06). This protective association of α-T was lost at higher γ-T levels. We did not see any consistent associations of second trimester levels of either α-T or γ-T with mid-childhood FEV₁ or FVC.

CONCLUSION

When γ-T levels were in the lowest tertile, a higher early-childhood α-T level was associated with better lung function at mid-childhood. Second trimester maternal plasma α-T concentration was 3-fold higher than in the adult nonpregnant female population.

Changes of DNA methylation are associated with changes in lung function during adolescence

BACKGROUND

Adolescence is a significant period for the gender-dependent development of lung function. Prior studies have shown that DNA methylation (DNA-M) is associated with lung function and DNA-M at some cytosine-phosphate-guanine dinucleotide sites (CpGs) changes over time. This study examined whether changes of DNA-M at lung-function-related CpGs are associated with changes in lung function during adolescence for each gender, and if so, the biological significance of the detected CpGs.

METHODS

Genome-scale DNA-M was measured in peripheral blood samples at ages 10 (n = 330) and 18 years (n = 476) from the Isle of Wight (IOW) birth cohort in United Kingdom, using Illumina Infinium arrays (450 K and EPIC). Spirometry was conducted at both ages. A training and testing method was used to screen 402,714 CpGs for their potential associations with lung function. Linear regressions were applied to assess the association of changes in lung function with changes of DNA-M at those CpGs potentially related to lung function. Adolescence-related and personal and family-related confounders were included in the model. The analyses were stratified by gender. Multiple testing was adjusted by controlling false discovery rate of 0.05. Findings were further examined in two independent birth cohorts, the Avon Longitudinal Study of Children and Parents (ALSPAC) and the Children, Allergy, Milieu, Stockholm, Epidemiology (BAMSE) cohort. Pathway analyses were performed on genes to which the identified CpGs were mapped.

RESULTS

For females, 42 CpGs showed statistically significant associations with change in FEV1/FVC, but none for change in FEV1 or FVC. No CpGs were identified for males. In replication analyses, 16 and 21 of the 42 CpGs showed the same direction of associations among the females in the ALSPAC and BAMSE cohorts, respectively, with 11 CpGs overlapping across all the three cohorts. Through pathway analyses, significant biological processes were identified that have previously been related to lung function development.

CONCLUSIONS

The detected 11 CpGs in all three cohorts have the potential to serve as the candidate epigenetic markers for changes in lung function during adolescence in females.

Why Do Intrauterine Exposure to Air Pollution and Cigarette Smoke Increase the Risk of Asthma?

The prevalence of childhood asthma is increasing worldwide and increased in utero exposure to environmental toxicants may play a major role. As current asthma treatments are not curative, understanding the mechanisms underlying the etiology of asthma will allow better preventative strategies to be developed. This review focuses on the current understanding of how in utero exposure to environmental factors increases the risk of developing asthma in children. Epidemiological studies show that maternal smoking and particulate matter exposure during pregnancy are prominent risk factors for the development of childhood asthma. We discuss the changes in the developing fetus due to reduced oxygen and nutrient delivery affected by intrauterine environmental change. This leads to fetal underdevelopment and abnormal lung structure. Concurrently an altered immune response and aberrant epithelial and mesenchymal cellular function occur possibly due to epigenetic reprograming. The sequelae of these early life events are airway remodeling, airway hyperresponsiveness, and inflammation, the hallmark features of asthma. In summary, exposure to inhaled oxidants such as cigarette smoking or particulate matter increases the risk of childhood asthma and involves multiple mechanisms including impaired fetal lung development (structural changes), endocrine disorders, abnormal immune responses, and epigenetic modifications. These make it challenging to reduce the risk of asthma, but knowledge of the mechanisms can still help to develop personalized medicines.

Lung functional development and asthma trajectories

Early life environmental risk factors are associated with chronic respiratory morbidity in child- and adulthood. A possible mechanism for this sustained effect is their influence on early life lung functional growth and development, a susceptible phase of rapid lung growth with increased plasticity. We summarize evidence of hereditary and environmental ante-, peri-, and early postnatal factors on lung functional development, such as air pollution, tobacco exposure, nutrition, intrauterine growth retardation, prematurity, early life infections, microbiome, and allergies and their effect on lung functional trajectories. While some of the factors (e.g., prematurity) directly impair lung growth, the influence of many environmental factors is mediated through inflammatory processes (e.g., recurrent infections or oxidative stress). The timing and nature of these influences and their impact result in degrees of impaired maximal lung functional capacity in early adulthood; and they potentially impact future long-term respiratory morbidity such as chronic asthma or chronic obstructive airway disease (COPD). We discuss possibilities to prevent or modify such early abnormal lung functional growth trajectories and the need for future studies and prevention programs.

Timing of secondhand smoke, pet, dampness or mould exposure and lung function in adolescence

BACKGROUND

The relevance of timing of exposure in the associations of secondhand tobacco smoke (SHS), pets, and dampness or mould exposure with lung function is unclear. We investigated the relevance of timing of these exposures for lung function in adolescence.

METHODS

We used data from participants of the Dutch Prevention and Incidence of Asthma and Mite Allergy (PIAMA) cohort with spirometric measurements at ages 12 and 16 years (n=552). Data on residential exposure to SHS, pets, and dampness or mould were obtained by repeated parental questionnaires. We characterised timing of exposure through longitudinal patterns using latent class growth modelling and assessed associations of these patterns with FEV₁ and FVC at ages 12 and 16 and FEV₁ and FVC growth between ages 12 and 16 using linear regression models.

RESULTS

Childhood SHS exposure was associated with reduced FEV₁ growth/year (95% CI) (-0.34% (-0.64% to -0.04%)). Late childhood and early life pet exposure was associated with increased FEV₁ growth (0.41% (0.14% to 0.67%)) and reduced FVC growth (-0.28% (-0.53% to -0.03%)), respectively, compared with very low exposure. Early life dampness or mould exposure was associated with reduced lung function growth. All time windows of SHS exposure tended to be associated with lower attained lung function and pet exposure tended to be associated with higher FEV₁.

CONCLUSION

SHS exposure during childhood could lead to reduced lung function growth and lower attained lung function in adolescence. While pet exposure in late childhood may not adversely affect lung function, early childhood pet exposure may slow down FVC growth in adolescence.

Interaction of Glutathione S-Transferase M1, T1, and P1 Genes With Early Life Tobacco Smoke Exposure on Lung Function in Adolescents

BACKGROUND

Glutathione S-transferase (GST) genes are involved in the management of oxidative stress in the lungs. We aimed to determine whether they modify the associations between early life smoke exposure and adverse lung health outcomes.

METHODS

The Melbourne Atopy Cohort study (a high-risk birth cohort) enrolled 620 children and followed them prospectively from birth. We recorded perinatal tobacco smoke exposure, asthma, and lung function at 12 (59%) and 18 years (66%) and genotyped for GSTM1, GSTT1, and GSTP1 (69%).

RESULTS

GST genotypes were found to interact with tobacco smoke exposure on lung function outcomes (P interaction ≤ .05). Only among children with GSTT1 null genotypes was exposure to mother's, father's, or parental tobacco smoke in early life associated with an increased risk of reductions in prebronchodilator (BD) FEV₁ and FVC at both 12 and 18 years. These associations were not seen in children with GSTT1 present. Similarly, only among children with GSTM1 null genotypes was exposure to father's or parental smoking associated with reductions in pre- and post-BD FEV₁ and FVC at 18 years. Only among children with Ile/Ile genotypes of GSTP1 was exposure to mother's smoking associated with increased risk of reduced FEV₁ at 18 years, but this was not the case among children with Val/Val or Ile/Val genotypes.

CONCLUSIONS

Our study provides evidence of interaction between early tobacco smoke exposure and GST genotypes on lung function. Carriers of GST null mutations and GSTP1 Ile/Ile alleles may be more susceptible when exposed to tobacco smoke in early life. These findings support stronger recommendations to protect all infants from tobacco smoke exposure.

TRIAL REGISTRY

Australian and New Zealand Clinical Trials Registry; No.: ACTRN12609000734268; URL: http://www.anzctr.org.au/.

Western Australian pregnancy cohort (Raine) Study: Generation 1

PURPOSE

The purpose of the Raine Study is to improve human health and well-being by studying the life-course of a cohort of Western Australians, based on a life-course conceptual framework that considers interactions between genetics, phenotypes, behaviours, the environment and developmental and social outcomes.

PARTICIPANTS

Between May 1989 and November 1991, 2900 pregnant women were enrolled in the Raine Study in Perth, Western Australia. In total, 2730 women gave birth to 2868 children (Generation 2) between August 1989 and April 1992. The mothers and fathers of Generation 2 are referred to as Generation 1 of the Raine Study. In the most recent Generation 1 follow-up, 636 mothers and 462 fathers participated.

FINDINGS TO DATE

Until the 26-year follow-up of Generation 1 the focus of research within the Raine Study was on outcomes in Generation 2, with information on the parents mainly being used to examine its influence on their children's outcomes. For example, recent findings showed that several characteristics of mothers, such as obesity, early mid-gestational weight gain and socioeconomic status were associated with non-alcoholic fatty liver disease, adiposity and cardiometabolic characteristics in offspring. Other findings showed that parents with back pain were more likely to have offspring who experienced back pain. Also, non-linear and dynamic relationships were found between maternal working hours and offspring overweight or obesity.

FUTURE PLANS

The Raine Study will continue to provide access to its dense longitudinal genetic, phenotypic, behavioural, environmental, developmental and social data to undertake studies with the ultimate goal of improving human health and well-being. Analyses of data from the recent Generation 1 year 26 follow-up are underway.

TRIAL REGISTRATION NUMBER

ACTRN12617001599369.

Epigenome-wide association study reveals methylation pathways associated with childhood allergic sensitization

Epigenetic mechanisms integrate both genetic variability and environmental exposures. However, comprehensive epigenome-wide analysis has not been performed across major childhood allergic phenotypes. We examined the association of epigenome-wide DNA methylation in mid-childhood peripheral blood (Illumina HumanMethyl450K) with mid-childhood atopic sensitization, environmental/inhalant and food allergen sensitization in 739 children in two birth cohorts (Project Viva-Boston, and the Generation R Study-Rotterdam). We performed covariate-adjusted epigenome-wide association meta-analysis and employed pathway and regional analyses of results. Seven-hundred and five methylation sites (505 genes) were significantly cross-sectionally associated with mid-childhood atopic sensitization, 1411 (905 genes) for environmental and 45 (36 genes) for food allergen sensitization (FDR<0.05). We observed differential methylation across multiple genes for all three phenotypes, including genes implicated previously in innate immunity (DICER1), eosinophilic esophagitis and sinusitis (SIGLEC8), the atopic march (AP5B1) and asthma (EPX, IL4, IL5RA, PRG2, SIGLEC8, CLU). In addition, most of the associated methylation marks for all three phenotypes occur in putative transcription factor binding motifs. Pathway analysis identified multiple methylation sites associated with atopic sensitization and environmental allergen sensitization located in/near genes involved in asthma, mTOR signaling, and inositol phosphate metabolism. We identified multiple differentially methylated regions associated with atopic sensitization (8 regions) and environmental allergen sensitization (26 regions). A number of nominally significant methylation sites in the cord blood analysis were epigenome-wide significant in the mid-childhood analysis, and we observed significant methylation - time interactions among a subset of sites examined. Our findings provide insights into epigenetic regulatory pathways as markers of childhood allergic sensitization.

Lung development and emerging roles for type 2 immunity

Lung development is a complex process mediated through the interaction of multiple cell types, factors and mediators. In mice, it starts as early as embryonic day 9 and continues into early adulthood. The process can be separated into five different developmental stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar. Whilst lung bud formation and branching morphogenesis have been studied extensively, the mechanisms of alveolarisation are incompletely understood. Aberrant lung development can lead to deleterious consequences for respiratory health such as bronchopulmonary dysplasia (BPD), a disease primarily affecting preterm neonates, which is characterised by increased pulmonary inflammation and disturbed alveolarisation. While the deleterious effects of type 1-mediated inflammatory responses on lung development have been well established, the role of type 2 responses in postnatal lung development remains poorly understood. Recent studies indicate that type 2-associated immune cells, such as group 2 innate lymphoid cells and alveolar macrophages, are increased in number during postnatal alveolarisation. Here, we present the current state of understanding of the postnatal stages of lung development and the key cell types and mediators known to be involved. We also provide an overview of how stem cells are involved in lung development and regeneration, and the negative influences of respiratory infections. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Primary Prevention of Airway Allergy

Purpose of review

The aim of this paper is to review and summarize the current knowledge of prevention of airway allergy.

Recent findings

Allergic rhinitis and asthma are allergic airway diseases. Due to their increasing incidence and socioeconomic burden, allergic airway diseases have recently gained attention worldwide. The primary prevention of allergic airway diseases focuses on offspring’s gestational and childhood environment, such as maternal smoking and diet during pregnancy and breastfeeding as well as exposure to environmental microbes and irritants.

Summary

Asthma and allergic rhinitis are a major public health problem worldwide. They have increasing prevalence and thus attempts to their prevention are mandatory. Rapid action needs to be taken to restrain smoking among children and adolescents in order to prevent burden of allergic airway diseases. Exposure to pollution and environmental issues concerning hygiene and lifestyle would also need to be actively addressed. More evidence is still needed in order to draw linings concerning maternal diet and other factors during the offspring’s whole life span.

Risk factors for chronic lung disease and asthma differ among children born extremely preterm

OBJECTIVES

To evaluate the hypothesis that chronic lung disease of prematurity (CLD) is a risk factor for asthma in children born extremely preterm, and the hypothesis that the risk factors for CLD are similar to those for asthma.

METHODS

A retrospective analysis was performed using data collected prospectively from 882 children born before the 28th week of gestation between 2002 and 2004 who returned for follow-up at ages 12 and 24 months and 10 years. We created time-oriented logistic regression models to compare risk factors for CLD, defined as need for supplemental oxygen at 36 weeks postmenstrual age, and parent-reported asthma at 10 years of age.

RESULTS

CLD diagnosed during neonatal admission was associated with bronchodilator use at 12 months and 24 months (P < 0.001), but not with an asthma diagnosis at 10 years (Odds Ratio 1.3; 95% confidence interval 0.98-1.8). While risk factors for CLD include lower gestational age (OR 2.7; 1.5-4.7) and fetal growth restriction (OR 2.3; 1.4-3.7), risk factors for asthma include mother's eligibility for public insurance (Medicaid) (OR 1.8; 1.1-2.8), and higher weight gain velocity during the first year (OR 1.5; 1.02-2.2) and between the 2nd and 10th year (OR 1.7; 1.2-2.4).

CONCLUSIONS

Among children born extremely preterm, the diagnosis of CLD and its antecedents were associated with transient preschool wheezing, but not with asthma. Post-NICU factors, such as growth velocity and socioeconomic disadvantage, appear to have stronger associations with asthma than exposures during NICU admission.

Lung function in adults born preterm

Very preterm birth, before the gestational age (GA) of 32 weeks, increases the risk of obstructed airflow in adulthood. We examined whether all preterm births (GA<37 weeks) are associated with poorer adult lung function and whether any associations are explained by maternal, early life/neonatal, or current life factors. Participants of the ESTER Preterm Birth Study, born between 1985 and 1989 (during the pre-surfactant era), at the age of 23 years participated in a clinical study in which they performed spirometry and provided detailed medical history. Of the participants, 139 were born early preterm (GA<34 weeks), 239 late preterm (GA: 34-<37 weeks), and 341 full-term (GA≥37 weeks). Preterm birth was associated with poorer lung function. Mean differences between individuals born early preterm versus full-term were -0.23 standard deviation (SD) (95% confidence interval (CI): -0.40, -0.05)) for forced vital capacity z-score (zFVC), -0.44 SD (95% CI -0.64, -0.25) for forced expiratory volume z-score (zFEV1), and -0.29 SD (95% CI -0.47, -0.10) for zFEV1/FVC. For late preterm, mean differences with full-term controls were -0.02 SD (95% CI -0.17, 0.13), -0.12 SD (95% CI -0.29, 0.04) and -0.13 SD (95% CI -0.29, 0.02) for zFVC, zFEV1, and zFEV1/FVC, respectively. Examination of finer GA subgroups suggested an inverse non-linear association between lung function and GA, with the greatest impact on zFEV1 for those born extremely preterm. The subgroup means were GA<28 weeks: -0.98 SD; 28-<32 weeks: -0.29 SD; 32-<34 weeks: -0.44 SD; 34-<36 weeks: -0.10 SD; 36-<37weeks: -0.11 SD; term-born controls (≥37weeks): 0.02 SD. Corresponding means for zFEV1/FVC were -1.79, -0.44, -0.47, -0.48, -0.29, and -0.02. Adjustment for maternal pregnancy conditions and socioeconomic and lifestyle factors had no major impact on the relationship. Preterm birth is associated with airflow limitation in adult life. The association appears to be attributable predominantly to those born most immature, with only a modest decrease among those born preterm at later gestational ages.

The toxicity of E-cigarettes and children's respiratory health

Electronic cigarettes (E-cig), also referred to as Electronic Nicotine Delivery System (ENDS), were initially developed in 2003 to reduce the harmful effects of tobacco smoking. Since then, E-cig have become widely available in many countries and are used by many young people who would be unlikely to take up cigarette smoking. However, the adverse effects on child health remain largely unknown. E-cigs are available through regulated sale in many countries, but easily accessible by the internet in others. Adverse effects may be ascribed to the nicotine itself, to the accompanying substances in the aerosol (often referred to as vapour) or to temperature modifications of the content. There is a lack of human studies to assess respiratory effects of nicotine exposure to the unborn or young child. Also assessing the effects of the vaping content apart from nicotine is challenging, with the huge variety of exposure by frequency, duration and content, but experimental studies are on the way that may indicate the level of harm by such products. This article will summarize what is currently known about the use of E-cigs in children and in pregnancy, and discuss adverse effects of direct or in utero exposure to E-cig on the respiratory health of children. We thereby hope to provide a background for discussing potential harms to the respiratory system of children by E-cig exposure in pregnancy and early post-natal life, in a setting where an increasing proportion of adolescent and young adults use E-cigs, marketed to be 95% less harmful than conventional cigarettes.

Self-reported prenatal tobacco smoke exposure, AXL gene-body methylation, and childhood asthma phenotypes

BACKGROUND

Epigenetic modifications, including DNA methylation, act as one potential mechanism underlying the detrimental effects associated with prenatal tobacco smoke (PTS) exposure. Methylation in a gene called AXL was previously reported to differ in response to PTS.

METHODS

We investigated the association between PTS and epigenetic changes in AXL and how this was related to childhood asthma phenotypes. We tested the association between PTS and DNA methylation at multiple CpG loci of AXL at birth using Pyrosequencing in two separate study populations, the Children's Health Study (CHS, n = 799) and the Newborn Epigenetic Study (NEST, n = 592). Plasma cotinine concentration was used to validate findings with self-reported smoking status. The inter-relationships among AXL mRNA and miR-199a1 expression, PTS, and AXL methylation were examined. Lastly, we evaluated the joint effects of AXL methylation and PTS on the risk of asthma and related symptoms at age 10 years old.

RESULTS

PTS was associated with higher methylation level in the AXL gene body in both CHS and NEST subjects. In the pooled analysis, exposed subjects had a 0.51% higher methylation level in this region compared to unexposed subjects (95% CI 0.29, 0.74; p < 0.0001). PTS was also associated with 21.2% lower expression of miR-199a1 (95% CI - 37.9, - 0.1; p = 0.05), a microRNA known to regulate AXL expression. Furthermore, the combination of higher AXL methylation and PTS exposure at birth increased the risk of recent episodes of bronchitic symptoms in childhood.

CONCLUSIONS

PTS was associated with methylation level of AXL and the combination altered the risk of childhood bronchitic symptoms.

[Maternal smoking during pregnancy: A risk factor for respiratory disorders in children]

Maternal smoking during pregnancy (MSDP) is a well-established risk factor for negative pregnancy outcomes, but its negative effects on the health of the child after birth are less well known by both health professionals and the general public. Large cohort studies over the past 10 years have shown that MSDP is an independent risk factor for several childhood health problems such as e.g. obesity and smoking. A large number of recent studies and 3 meta-analyses demonstrate that MSDP is an independent risk factor of wheezing and asthma of the child exposed in utero to maternal smoking. MSDP is associated with epigenetic toxicities the currently most plausible hypothesis to explain the diversity of its postnatal negative effects. The eradication of MSDP could contribute to the reduction of health problems in the next generation, including the incidence of childhood respiratory disorders.

Air pollutants and early origins of respiratory diseases

Air pollution is a global health threat and causes millions of human deaths annually. The late onset of respiratory diseases in children and adults due to prenatal or perinatal exposure to air pollutants is emerging as a critical concern in human health. Pregnancy and fetal development stages are highly susceptible to environmental exposure and tend to develop a long-term impact in later life. In this review, we briefly glance at the direct impact of outdoor and indoor air pollutants on lung diseases and pregnancy disorders. We further focus on lung complications in later life with early exposure to air pollutants. Epidemiological evidence is provided to show the association of prenatal or perinatal exposure to air pollutants with various adverse birth outcomes, such as preterm birth, lower birth weight, and lung developmental defects, which further associate with respiratory diseases and reduced lung function in children and adults. Mechanistic evidence is also discussed to support that air pollutants impact various cellular and molecular targets at early life, which link to the pathogenesis and altered immune responses related to abnormal respiratory functions and lung diseases in later life.

Tobacco smoke exposure in early life and adolescence in relation to lung function

Maternal smoking during pregnancy is associated with impaired lung function among young children, but less is known about long-term effects and the impact of adolescents' own smoking. We investigated the influence of maternal smoking during pregnancy, secondhand smoke exposure and adolescent smoking on lung function at age 16 years.

The BAMSE (Barn/Child, Allergy, Milieu, Stockholm, Epidemiology) birth cohort collected information on participants' tobacco smoke exposure through repeated questionnaires, and measured saliva cotinine concentrations at age 16 years. Participants performed spirometry and impulse oscillometry (IOS) at age 16 years (n=2295).

Exposure to maternal smoking during pregnancy was associated with reduced forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) ratio of −1.1% (95% CI −2.0 to −0.2%). IOS demonstrated greater resistance at 5–20 Hz (R_5–20) in participants exposed to maternal smoking during pregnancy. Adolescents who smoked had reduced FEV₁/FVC ratios of −0.9% (95% CI −1.8 to −0.1%) and increased resistance of 6.5 Pa·L^–1·s (95% CI 0.7 to 12.2 Pa·L^–1·s) in R_5–20. Comparable associations for FEV₁/FVC ratio were observed for cotinine concentrations, using ≥12 ng·mL⁻¹ as a cut-off for adolescent smoking.

Maternal smoking during pregnancy was associated with lower FEV₁/FVC ratios and increased airway resistance. In addition, adolescent smoking appears to be associated with reduced FEV₁/FVC ratios and increased peripheral airway resistance.

Maternal smoking in utero and teenage smoking are associated with indices of airway obstruction at age 16 yearshttp://ow.ly/NwF030jFS2W

Education is the strongest socio-economic predictor of smoking in pregnancy

AIMS

To investigate socio-economic disparities in smoking in pregnancy (SIP) by the mother's education, occupational class and current economic conditions.

DESIGN

Cross-sectional analysis with linked survey and register data.

SETTING

South-western Finland.

PARTICIPANTS

A total of 2667 pregnant women [70% of the original sample (n = 3808)] from FinnBrain, a prospective pregnancy cohort study.

MEASUREMENTS

The outcome was smoking during the first pregnancy trimester, measured from the Finnish Medical Birth Register. Education and occupational class were linked from population registers. Income support recipiency and subjective economic wellbeing were questionnaire-based measures of current economic conditions. These were adjusted for age, partnership status, residential area type, parental separation, parity, childhood socio-economic background, childhood adversities (the Trauma and Distressing Events During Childhood scale) and antenatal stress (Edinburgh Postnatal Depression Scale). Logistic regressions and attributable fractions (AF) were estimated.

FINDINGS

Mother's education was the strongest socio-economic predictor of SIP. Compared with university education, adjusted odds ratios (aORs) of SIP were: 2.2 [95% confidence interval (CI) = 1.2-3.9; P = 0.011] for tertiary vocational education, 4.4 (95% CI = 2.1-9.0; P < 0.001) for combined general and vocational secondary education, 2.9 (95% CI = 1.4-6.1; P = 0.006) for general secondary education, 9.5 (95% CI 5.0-18.2; P < 0.001) for vocational secondary education and 14.4 (95% CI = 6.3-33.0; P < 0.001) for compulsory schooling. The total AF of education was 0.5. Adjusted for the other variables, occupational class and subjective economic wellbeing did not predict SIP. Income support recipiency was associated positively with SIP (aOR = 1.8; 95% CI = 1.1-3.1; P = 0.022). Antenatal stress predicted SIP (aOR = 2.0; 95% CI = 1.4-2.8; P < 0.001), but did not attenuate its socio-economic disparities.

CONCLUSIONS

In Finland, socio-economic disparities in smoking in pregnancy are attributable primarily to differences in the mother's educational level (low versus high) and orientation (vocational versus general).

Intrauterine smoke exposure deregulates lung function, pulmonary transcriptomes, and in particular insulin-like growth factor (IGF)-1 in a sex-specific manner

Prenatal exposure to tobacco smoke is a significant risk-factor for airway disease development. Furthermore, the high prevalence of pregnant smoking women requires the establishment of strategies for offspring lung protection. Therefore, we here aimed to understand the molecular mechanism of how prenatal smoke exposure affects fetal lung development. We used a mouse model recapitulating clinical findings of prenatally exposed children, where pregnant mice were exposed to smoke until c-section or spontaneous delivery, and offspring weight development and lung function was monitored. Additionally, we investigated pulmonary transcriptome changes in fetal lungs (GD18.5) by mRNA/miRNA arrays, network analyses and qPCR. The results demonstrated that prenatally exposed mice showed intrauterine and postnatal growth retardation, and impaired lung function. 1340 genes and 133 miRNAs were found to be significantly dysregulated by in utero smoke exposure, and we identified Insulin-like growth factor 1 (Igf1) as a top hierarchical node in a network analysis. Moreover, Igf1 mRNA was increased in female murine offspring and in prenatally exposed children. These findings suggest that prenatal smoking is associated with a dysregulation of several genes, including Igf1 in a sex-specific manner. Thus, our results could represent a novel link between smoke exposure, abberant lung development and impaired lung function.

Maternal Smoking during Pregnancy and Early Childhood and Development of Asthma and Rhinoconjunctivitis - a MeDALL Project

BACKGROUND

The role of tobacco smoke exposure in the development and persistence of asthma and rhinoconjunctivitis through childhood into adolescence is unclear.

OBJECTIVES

We assessed the associations of parental smoking from fetal life through adolescence with asthma and rhinoconjunctivitis during childhood and adolescence.

METHODS

We analyzed data for 10,860 participants of five European birth cohort studies from the Mechanisms of the Development of Allergy (MeDALL) consortium. Parental smoking habits and health outcomes (early transient, persistent, and adolescent-onset asthma and rhinoconjunctivitis) were based on questionnaires covering the period from pregnancy to 14-16 y of age. Data were combined and analyzed using a one-stage and two-stage individual participant data meta-analysis.

RESULTS

Overall, any maternal smoking during pregnancy tended to be associated with an increased odds of prevalent asthma [adjusted odds ratio (aOR)=1.19 (95% CI: 0.98, 1.43)], but not prevalent rhinoconjunctivitis [aOR=1.05 (95% CI: 0.90, 1.22)], during childhood and adolescence. In analyses with phenotypes related to age of onset and persistence of disease, any maternal smoking during pregnancy was associated with early transient asthma [aOR=1.79 (95% CI: 1.14, 2.83)]. Maternal smoking of ≥10 cigarettes/day during pregnancy was associated with persistent asthma [aOR=1.66 (95% CI: 1.29, 2.15)] and persistent rhinoconjunctivitis [aOR=1.55 (95% CI, 1.09, 2.20)]. Tobacco smoke exposure during fetal life, infancy, childhood, and adolescence was not associated with adolescent-onset asthma or rhinoconjunctivitis.

CONCLUSIONS

Findings from this combined analysis of five European birth cohorts strengthen evidence linking early exposure to tobacco smoke with asthma during childhood and adolescence. Children with high early-life exposure were more likely than unexposed children to have early transient and persistent asthma and persistent rhinoconjunctivitis. https://doi.org/10.1289/EHP2738.

Factors Affecting Lung Function: A Review of the Literature

Lung function reference values are traditionally based on anthropometric factors, such as weight, height, sex, and age. FVC and FEV₁ decline with age, while volumes and capacities, such as RV and FRC, increase. TLC, VC, RV, FVC and FEV₁ are affected by height, since they are proportional to body size. This means that a tall individual will experience greater decrease in lung volumes as they get older. Some variables, such as FRC and ERV, decline exponentially with an increase in weight, to the extent that tidal volume in morbidly obese patients can be close to that of RV. Men have longer airways than women, causing greater specific resistance in the respiratory tract. The increased work of breathing to increase ventilation among women means that their consumption of oxygen is higher than men under similar conditions of physical intensity. Lung volumes are higher when the subject is standing than in other positions. DLCO is significantly higher in supine positions than in sitting or standing positions, but the difference between sitting and standing positions is not significant. Anthropometric characteristics are insufficient to explain differences in lung function between different ethnic groups, underlining the importance of considering other factors in addition to the conventional anthropometric measurements.

Air Pollution and Dispensed Medications for Asthma, and Possible Effect Modifiers Related to Mental Health and Socio-Economy: A Longitudinal Cohort Study of Swedish Children and Adolescents

It has been suggested that children that are exposed to a stressful environment at home have an increased susceptibility for air pollution-related asthma. The aim here was to investigate the association between air pollution exposure and asthma, and effect modification by mental health and by socio-economic status (as markers of a stressful environment). All individuals under 18 years of age in four Swedish counties during 2007 to 2010 (1.2 million people) were included. The outcome was defined as dispensing at least two asthma medications during follow up. We linked data on NO₂ from an empirical land use regression to data from national registers on outcome and potential confounders. Data was analyzed with logistic regression. There was an odds ratio (OR) of 1.02 (95% Confidence Interval (CI: 1.01–1.03) for asthma associated with a 10 µg·m⁻³ increase in NO₂. The association only seemed to be present in areas where NO₂ was higher than 15 µg·m⁻³ with an OR of 1.09 (95% CI: 1.07–1.12), and the association seemed stronger in children with parents with a high education, OR = 1.05 (95% CI: 1.02–1.09) and OR = 1.04 (95% CI: 1.01–1.07) in children to mothers and father with a high education, respectively. The association did not seem to depend on medication history of psychiatric disorders. There was weak evidence for the association between air pollution and asthma to be stronger in neighborhoods with higher education levels. In conclusion, air pollution was associated with dispensed asthma medications, especially in areas with comparatively higher levels of air pollution, and in children to parents with high education. We did not observe support for our hypothesis that stressors linked to socio-economy or mental health problems would increase susceptibility to the effects of air pollution on the development of asthma.

Vitamin C Prevents Offspring DNA Methylation Changes Associated with Maternal Smoking in Pregnancy

RATIONALE

Infants whose mothers smoked during pregnancy demonstrate lifelong decreases in pulmonary function. DNA methylation changes associated with maternal smoking during pregnancy have been described in placenta and cord blood at delivery, in fetal lung, and in buccal epithelium and blood during childhood. We demonstrated in a randomized clinical trial ( ClinicalTrials.gov identifier, NCT00632476) that vitamin C supplementation to pregnant smokers can lessen the impact of maternal smoking on offspring pulmonary function and decrease the incidence of wheeze at 1 year of age.

OBJECTIVES

To determine whether vitamin C supplementation reduces changes in offspring methylation in response to maternal smoking and whether methylation at specific CpGs is also associated with respiratory outcomes.

METHODS

Targeted bisulfite sequencing was performed with a subset of placentas, cord blood samples, and buccal samples collected during the NCT00632476 trial followed by independent validation of selected cord blood differentially methylated regions, using bisulfite amplicon sequencing.

MEASUREMENTS AND MAIN RESULTS

The majority (69.03%) of CpGs with at least 10% methylation difference between placebo and nonsmoker groups were restored (by at least 50%) toward nonsmoker levels with vitamin C treatment. A significant proportion of restored CpGs were associated with phenotypic outcome with greater enrichment among hypomethylated CpGs.

CONCLUSIONS

We identified a pattern of normalization in DNA methylation by vitamin C supplementation across multiple loci. The consistency of this pattern across tissues and time suggests a systemic and persistent effect on offspring DNA methylation. Further work is necessary to determine how genome-wide changes in DNA methylation may mediate or reflect persistent effects of maternal smoking on lung function.

Antenatal Determinants of Bronchopulmonary Dysplasia and Late Respiratory Disease in Preterm Infants

RATIONALE

Mechanisms contributing to chronic lung disease after preterm birth are incompletely understood.

OBJECTIVES

To identify antenatal risk factors associated with increased risk for bronchopulmonary dysplasia (BPD) and respiratory disease during early childhood after preterm birth, we performed a prospective, longitudinal study of 587 preterm infants with gestational age less than 34 weeks and birth weights between 500 and 1,250 g.

METHODS

Data collected included perinatal information and assessments during the neonatal intensive care unit admission and longitudinal follow-up by questionnaire until 2 years of age.

MEASUREMENTS AND MAIN RESULTS

After adjusting for covariates, we found that maternal smoking prior to preterm birth increased the odds of having an infant with BPD by twofold (P = 0.02). Maternal smoking was associated with prolonged mechanical ventilation and respiratory support during the neonatal intensive care unit admission. Preexisting hypertension was associated with a twofold (P = 0.04) increase in odds for BPD. Lower gestational age and birth weight z-scores were associated with BPD. Preterm infants who were exposed to maternal smoking had higher rates of late respiratory disease during childhood. Twenty-two percent of infants diagnosed with BPD and 34% of preterm infants without BPD had no clinical signs of late respiratory disease during early childhood.

CONCLUSIONS

We conclude that maternal smoking and hypertension increase the odds for developing BPD after preterm birth, and that maternal smoking is strongly associated with increased odds for late respiratory morbidities during early childhood. These findings suggest that in addition to the BPD diagnosis at 36 weeks, other factors modulate late respiratory outcomes during childhood. We speculate that measures to reduce maternal smoking not only will lower the risk for preterm birth but also will improve late respiratory morbidities after preterm birth.