In utero and postnatal maternal smoking and asthma in adolescence

The impact of exposure to tobacco smoke and e-cigarettes on asthma-related outcomes: Systematic review informing the EAACI guidelines on environmental science for allergic diseases and asthma

To inform the clinical practice guidelines' recommendations developed by the European Academy of Allergy and Clinical Immunology systematic reviews (SR) assessed using GRADE on the impact of environmental tobacco smoke (ETS) and active smoking on the risk of new-onset asthma/recurrent wheezing (RW)/low lung function (LF), and on asthma-related outcomes. Only longitudinal studies were included, almost all on combustion cigarettes, only one assessing e-cigarettes and LF. According to the first SR (67 studies), prenatal ETS increases the risk of RW (moderate certainty evidence) and may increase the risk of new-onset asthma and of low LF (low certainty evidence). Postnatal ETS increases the risk of new-onset asthma and of RW (moderate certainty evidence) and may impact LF (low certainty evidence). Combined in utero and postnatal ETS may increase the risk of new-onset asthma (low certainty evidence) and increases the risk of RW (moderate certainty evidence). According to the second SR (24 studies), ETS increases the risk of severe asthma exacerbations and impairs asthma control and LF (moderate certainty evidence). According to the third SR (25 studies), active smoking increases the risk of severe asthma exacerbations and of suboptimal asthma control (moderate certainty evidence) and may impact asthma-related quality-of-life and LF (low certainty evidence).

Maternal occupational exposure to asthmogenic during pregnancy and the future risk of asthma in children: A meta-analysis

The association between maternal occupational exposure during pregnancy and the subsequent development of asthma in their children has always been a matter of debate, and the results of cohort studies on this issue have been controversial. The current study is the first systematic review and meta-analysis aimed at evaluating the risk of developing subsequent asthma in children based on maternal occupational exposure during the gestation period. To retrieve eligible studies, an advanced literature search was performed up to August 10, 2023 from the following databases: PubMed, Scopus, and Google Scholars. The title and abstract of related articles were screened; hence, the full texts were reviewed. Data extraction was conducted; hence, the included articles were analyzed to assess the mention association. From a total of 10 cohort studies with a total record of 5372, it was found that there is no significant relationship between occupational exposure to asthmogenic during pregnancy and later asthma in children. The pooled odds ratio of asthmatic children in patients with maternal occupational exposure to asthmogenic during pregnancy was 1.03 (95% confidence interval, 0.97-1.09) I2= 13% p=0.62. It was concluded that there is no significant association between maternal occupational exposure and future asthma in children. However, future large-scale studies are required to support these results.

The relationship of early-life household air pollution with childhood asthma and lung function

The increase in childhood asthma over the past few decades has made it an important public health issue. Poor lung function growth associated with some phenotypes of asthma compounds its long-term impact on the individual. Exposure to early-life household risk factors is believed to be linked with respiratory health while infants' lungs are still developing. This review summarises epidemiological studies and mechanistic evidence focusing on the detrimental effects of early-life household air exposures on the respiratory health of children, in particular effects on asthma and lung function. Many early-life household air exposures, including tobacco smoke, gases from heating and cooking, mould/dampness and cleaning products are associated with childhood asthma development and lung function growth. These exposures may alter structural and mechanical characteristics of infants' lungs and contribute to deficits in later life. In addition, some risk factors, including tobacco smoke and cleaning products, can transmit effects across generations to increase the risk of asthma in subsequent generations. This review supports the hypothesis that risks of asthma and accelerated lung ageing are established in early life. The timing of exposure may be critical in the pathogenesis of respiratory diseases, in terms of future risk of asthma and reduced lung function in adults.

Neurological repercussions of neonatal nicotine exposure: A review

Smoking during pregnancy is hazardous to both the mother and the foetus, according to a substantial amount of recorded data. Exposure to nicotine and other compounds in cigarette smoke increases the risk of sudden infant death syndrome (SIDS) by two to five times during pregnancy. Serotonergic abnormalities have been discovered in SIDS infants in the zone of the medulla oblongata, which is known to control cardio-respiratory function. SIDS establishes a connection between depression, learning difficulties and behavioural disorders. Prenatal nicotine intake during the second trimester affects the dopaminergic neurological system, making the foetal brain more susceptible to nicotine and developing ADHD symptoms not just in a foetus but in adolescents also. Prenatal nicotine exposure alters the neurological route of neurotransmitters, acetylcholine and dopamine. Nicotine enhances neuronal activity in adults but desensitizes these processes in babies and young children exposed prenatally. The impact of a neurotoxin like nicotine is determined by the amount and duration of exposure. Continued exposure throughout pregnancy will influence a wide range of activities in the neurodevelopment, whereas exposure confined to a single stage of pregnancy may only affect the processes that are forming at that stage. To decrease the effect of nicotine on neonates due to maternal smoking strategies like nicotine replacement therapy (NRT), folic acid treatment and other behavioural treatments have been studied. Hence, this review focuses on the impact of exposure to nicotine on neonates, which results in various neurological consequences and smoking cessation therapies.

Sex-specific effects of in utero and adult tobacco smoke exposure

Tobacco smoke has harmful effects on a multiorgan level. Exposure to smoke, whether in utero or environmental, significantly increases susceptibility. This susceptibility has been identified to be divergent between males and females. However, there remains a distinct lack of thorough research into the relationship between sex and exposure to tobacco. Females tend to generate a more significant response than males during adulthood exposure. The intrauterine environment is meticulously controlled, and exposure to tobacco presents a significant factor that contributes to poor health outcomes and susceptibility later in life. Analysis of these effects in relation to the sex of the offspring is yet to be holistically reviewed and summarized. In this review, we will delineate the time-dependent relationship between tobacco smoke exposure and sex-specific disease susceptibility. We further outline possible biological mechanisms that may contribute to the identified pattern.

In utero Exposure to Nicotine Containing Electronic Cigarettes Increases the Risk of Allergic Asthma in Female Offspring

E-cigarettes (eCig) are being considered as an alternative to quit cigarette smoking while their long-term effect on lung pathophysiology are unknown. Maternal eCig-vaping may be promoted and considered as a safer cigarette smoking-replacement during pregnancy thus needing further assessment. Using murine models of in utero vaping and allergic asthma with complementary in vitro experiments we tested whether maternal eCig vaping enhances features of allergic asthma in offspring. Female BALB/c mice were exposed to either eCig vapor (± nicotine) or room air. Female offspring from these mothers were subjected to an ovalbumin (OVA)-induced allergic asthma model. Lung function and airway inflammation was assessed. Tissues were histologically assessed with H&E, Periodic Acid-Schiff and Masson's trichrome. Mitochondrial homeostasis protein expression was measured using immunohistochemistry while human airway smooth muscle (ASM) and Beas-2B cells were used to further measure cellular function and mitochondrial respiration. Allergen-challenge in mice lead to significant increase in airway inflammation, development of airway hyperresponsiveness (AHR) and increase in mucus and airway wall thickening (hallmark features of allergic asthma). Allergic asthma features were significantly enhanced in offspring from eCig (+Nicotine)-exposed mothers and were mainly reliant upon Th2-dependent inflammation with complementary changes in mitochondrial homeostasis. Further, in vitro data demonstrated that eCig (±Nicotine)-exposure impaired airway cell homeostasis and perturbed mitochondrial function. Collectively, maternal eCig vaping enhanced and worsened features of allergic asthma and this could partly be attributed to aberrant mitochondrial function.

Prenatal smoke effect on mouse offspring Igf1 promoter methylation from fetal stage to adulthood is organ and sex specific

Prenatal smoke exposure (PSE) is associated with reduced birth weight, impaired fetal development, and increased risk for diseases later in life. Changes in DNA methylation may be involved, as multiple large-scale epigenome-wide association studies showed that PSE is robustly associated with DNA methylation changes in blood among offspring in early life. Insulin-like growth factor-1 (IGF1) is important in growth, differentiation, and repair processes after injury. However, no studies investigated the organ-specific persistence of PSE-induced methylation change of Igf1 into adulthood. Based on our previous studies on the PSE effect on Igf1 promoter methylation in fetal and neonatal mouse offspring, we now have extended our studies to adulthood. Our data show that basal Igf1 promoter methylation generally increased in the lung but decreased in the liver (except for 2 persistent CpG sites in both organs) across three different developmental stages. PSE changed Igf1 promoter methylation in all three developmental stages, which was organ and sex specific. The PSE effect was less pronounced in adult offspring compared with the fetal and neonatal stages. In addition, the PSE effect in the adult stage was more pronounced in the lung compared with the liver. For most CpG sites, an inverse correlation was found for promoter methylation and mRNA expression when the data of all three stages were combined. This was more prominent in the liver. Our findings provide additional evidence for sex- and organ-dependent prenatal programming, which supports the developmental origins of health and disease (DOHaD) hypothesis.

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.

Predicting Lung Health Trajectories for Survivors of Preterm Birth

Rates of preterm birth (<37 weeks of gestation) are increasing worldwide. Improved perinatal care has markedly increased survival of very (<32 weeks gestation) and extremely (<28 weeks gestation) preterm infants, however, long term respiratory sequalae are common among survivors. Importantly, individual's lung function trajectories are determined early in life and tend to track over the life course. Preterm infants are impacted by antenatal, postnatal and early life perturbations to normal lung growth and development, potentially resulting in significant shifts from the "normal" lung function trajectory. This review summarizes what is currently known about the long-term lung function trajectories in survivors of preterm birth. Further, this review highlights how antenatal, perinatal and early life factors are likely to contribute to individual lung health trajectories across the life course.

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/.

[Toxic Components of PM2.5 and Their Toxicity Mechanisms-On the Toxicity of Sulfate and Carbon Components]

Recently, the main air pollutant has been fine particulate matter (PM_2.5), which is taken up by the whole body with severe adverse health effects. The main chemical components of PM_2.5 are salts of sulfate (and nitrate) and carbons. However, it remains unknown which components are toxic. Here, the author reviewed the literatures to determine which components are toxic and the main mechanisms underlying their toxicity. Many epidemiological studies have shown that sulfate concentration is strongly related to mortality. However, there is no experimental evidence showing that sulfate at environmental concentrations of PM_2.5 causes cardiovascular disease or other disease. On the other hand, carbon components such as elementary carbon (EC) produces high concentrations of reactive oxygen species (ROS) via its phagocytosis by macrophages, and organic carbon (OC) also produces high concentrations of ROS during its metabolic processes, and the ROS cause acute and chronic inflammation. They cause many diseases including cardiovascular disease, asthma and cancer. Furthermore, there are many lines of evidence showing that epigenetic changes such as DNA methylation or microRNA expression induced by particulate matters also induce the development of many diseases such as those mentioned above. It has been reported that carbon components are incorporated into the brain and produce ROS, and that the ROS cause damage to brain cells and Alzheimer's disease and cognitive disorders in the elderly.From these lines of evidence, the author would like to emphasize that the main toxicity of PM_2.5 is due to carbon components, and it is important to take countermeasures to decrease the concentration of carbon components in ambient air.

Genomic Predictors of Asthma Phenotypes and Treatment Response

Asthma is a complex respiratory disease considered as the most common chronic condition in children. A large genetic contribution to asthma susceptibility is predicted by the clustering of asthma and allergy symptoms among relatives and the large disease heritability estimated from twin studies, ranging from 55 to 90%. Genetic basis of asthma has been extensively investigated in the past 40 years using linkage analysis and candidate-gene association studies. However, the development of dense arrays for polymorphism genotyping has enabled the transition toward genome-wide association studies (GWAS), which have led the discovery of several unanticipated asthma genes in the last 11 years. Despite this, currently known risk variants identified using many thousand samples from distinct ethnicities only explain a small proportion of asthma heritability. This review examines the main findings of the last 2 years in genomic studies of asthma using GWAS and admixture mapping studies, as well as the direction of studies fostering integrative perspectives involving omics data. Additionally, we discuss the need for assessing the whole spectrum of genetic variation in association studies of asthma susceptibility, severity, and treatment response in order to further improve our knowledge of asthma genes and predictive biomarkers. Leveraging the individual's genetic information will allow a better understanding of asthma pathogenesis and will facilitate the transition toward a more precise diagnosis and treatment.

The association between substantiated childhood maltreatment, asthma and lung function: A prospective investigation

BACKGROUND

Asthma reflects multiple and likely complex causal pathways. We investigate the possibility that childhood maltreatment is one such causal pathway. Childhood maltreatment can be interpreted as a form of early life adversity and like other life adversities may predict a range of negative health outcomes, including asthma.

METHODS

A total of 3762 young adults (52.63% female) from the Mater Hospital-University of Queensland Study of Pregnancy (MUSP) participated in this study. MUSP is a prospective Australian birth cohort study of mothers consecutively recruited during their first antenatal clinic visit at Brisbane's Mater Hospital from 1981 to 1983. The study followed both mother-child dyads to the age of 21years after birth. Participants reported whether they had been diagnosed by a physician with asthma by the 21-year follow-up. Trained research assistants also performed gender- and height-standardized lung function tests using a Spirobank G spirometer system attached to a laptop computer. We linked this dataset with data obtained from the child protection services and which comprised all substantiated cases of childhood maltreatment in the MUSP cohort. Substantiations of childhood maltreatment included children in an age range of 0-14years.

RESULTS

The experience of any childhood maltreatment, particularly emotional abuse, was independently associated with self-reported physician-diagnosed asthma by the 21-year follow-up. The association was no longer significant after adjustment for a range of confounders and covariates in neglected children. Childhood maltreatment, including multiple events, was not associated with lung function in adjusted models.

CONCLUSIONS

Childhood maltreatment, including emotional abuse, was associated with lifetime ever asthma. This was in contrast to the absence of an association with objective measures of lung function. More research is indicated on the effect of childhood maltreatment on lung function using objective measures. In the meantime, there should be a greater awareness of the potential impact of childhood maltreatment on the potential to develop asthma, as well as of the possibility that asthma in adulthood may precede childhood maltreatment.

Lifetime secondhand smoke exposure and childhood and adolescent asthma: findings from the PIAMA cohort

BACKGROUND

Secondhand smoke (SHS) exposure is a modifiable risk factor associated with childhood asthma. Associations with adolescent asthma and the relevance of the timing and patterns of exposure are unclear. Knowledge of critical windows of exposure is important for targeted interventions.

METHODS

We used data until age 17 from 1454 children of the Dutch population-based PIAMA birth cohort. Residential SHS exposure was assessed through parental questionnaires completed at ages 3 months, 1-8 (yearly), 11, 14, and 17 years. Lifetime exposure was determined as; a) time window-specific exposure (prenatal, infancy, preschool, primary school, and secondary school); b) lifetime cumulative exposure; c) longitudinal exposure patterns using latent class growth modeling (LCGM). Generalized estimation equations and logistic regression were used to analyze associations between exposure and asthma at ages 4 to 17 years, adjusting for potential confounders.

RESULTS

With all three methods, we consistently found no association between SHS exposure and asthma at ages 4 to 17 years e.g. adjusted overall odds ratio (95% confidence interval) 0.67 (0.41-1.12), 1.00 (0.66-1.51) and 0.67 (0.41-1.11) for prenatal maternal active smoking, infancy, and preschool school time window exposures, respectively.

CONCLUSION

We assessed lifetime SHS exposure using different methods. Different timing and patterns of SHS exposure were not associated with an increased risk of asthma in childhood and adolescence in our study. More longitudinal studies could investigate effects of lifetime SHS exposure on asthma in adolescence and later life.

Asthma and sleep disturbance in adolescents and young adults: A cohort study

AIMS

A longitudinal birth cohort provides an opportunity to study the impact of childhood conditions persisting into adulthood. This study examines the cross-sectional association of asthma with sleep quality and snoring in the adolescent and young adult population and the extent to which asthma, sleep quality and snoring at 14 years independently predict themselves or each other at 21 years.

METHODS

Data from a 21-year follow-up of mothers and their children recruited into the Mater-University of Queensland Study of Pregnancy (n = 7223). Complete asthma and sleep information (questionnaire data) was available for 5015 participants at 14 years and 3527 at 21 years, with 3237 participants at both 14 and 21 years.

RESULTS

Poor sleep quality and snoring were independently associated with asthma at 14 years and 21 years, with stronger associations evident in women. At 21 years, associations were mediated by asthma symptom severity. Asthma, sleep quality and snoring at 14 years each strongly and independently predicted themselves at 21 years. Asthma at 14 years predicted snoring at 21 years, while poor sleep quality and snoring in women predicted asthma at 21 years, the latter partially mediated by body mass index.

CONCLUSIONS

The relationship between asthma, sleep quality and snoring varied by gender. Sleep quality and snoring should be considered in the assessment and holistic management of asthma. The predictive relationship seen between 14 and 21 years provides an opportunity to address these issues at a younger age.

Early smoke exposure is associated with asthma and lung function deficits in adolescents

OBJECTIVE

Early life tobacco smoke exposure may influence asthma, lung function and lung function growth into adolescence. We aimed to determine the associations between perinatal smoke exposure and asthma and lung function up to 18 years of age.

METHODS

We prospectively recorded perinatal parental smoking and measured respiratory outcomes at 12 and 18 years in the Melbourne Atopy Cohort Study (MACS), a longitudinal birth cohort. Multiple logistic regression was used to analyse the associations between perinatal smoke exposure and asthma at 12 (n = 370) and 18 years (n = 411). Multiple linear regression was used to investigate the relationship between perinatal smoking and: lung function (12 and 18 years) and lung function growth (between 12 and 18 years).

RESULTS

At 18 years, girls exposed to parental smoking during the perinatal period had increased odds of asthma (OR: 3.45, 95%CI: 1.36, 8.77), reduced pre-bronchodilator Forced expiratory volume in one-second (FEV₁) (-272 ml/s; -438, -107); FEV₁/ forced vital capacity (FVC) (-0.038; -0.065, -0.010); mid expiratory flow (MEF_25-75) (-430 ml/s; -798, -61), and reduced post-bronchodilator FEV₁/FVC (-0.028, -0.053, -0.004). No associations were found for boys (pre-bronchodilator FEV₁ 26ml/s; -202, 255; FEV₁/FVC 0.018; -0.013, 0.049).

CONCLUSIONS

Perinatal smoke may affect risk of asthma, reduce lung function and lung function growth in adolescence. Girls appear to be more susceptible than boys.

Maternal Folic Acid Supplementation During Pregnancy and Early Childhood Asthma

BACKGROUND

Asthma is one of the most common chronic childhood diseases. While folic acid supplementation around conception helps prevent neural tube defects, an animal model suggests that it may be a risk factor for respiratory diseases, although epidemiologic studies have had conflicting results. We investigated the timing of folic acid-containing prescription filling during pregnancy and child asthma.

METHODS

In a retrospective cohort study of 104,428 children, born 1996-2005, and their mothers enrolled in Tennessee Medicaid, we investigated the association of filling folic acid-containing prescriptions during pregnancy and childhood asthma at ages 4.5-6 years. We categorized women into exposure groups based on prescription filling centered around the first trimester: no folic acid prescription exposure, exposure in first trimester only, exposure after first trimester, and exposure in first trimester and beyond. We defined asthma using asthma-specific healthcare visits and medication fills. Using logistic regression models, we investigated the relationship adjusting for potential confounders.

RESULTS

Overall 15% of children had asthma. Compared with children born to women with no folic acid prescription exposure, children born to women with exposures in the first trimester only or first trimester and later had increased relative odds of asthma (adjusted odds ratios = 1.2, 95% confidence interval = 1.1, 1.3, and 1.2, 95% confidence interval = 1.2, 1.3); no association was seen in children born to women exposed after the first trimester.

CONCLUSION

Timing of folic acid-containing prescription filling during pregnancy was associated with childhood asthma. Our findings contribute to understanding of the role of prenatal nutritional supplements on child respiratory health.

Social Disparities in Maternal Smoking during Pregnancy: Comparison of Two Birth Cohorts (1996-2002 and 2003-2012) Based on Data from the German KiGGS Study

Background: Maternal smoking during pregnancy represents a significant developmental risk for the unborn child. This study investigated social differences in maternal smoking behavior during pregnancy in mothers living in Germany. The study focused on maternal age at delivery, social status and migration background. Method: The evaluation of data was based on two surveys carried out as part of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) carried out in 2003-2006 and in 2009-2012. The study compared the information given by parents of children aged between 0 and 6 years who were born either in the period from 1996 to  2002 (KiGGS baseline study, n = 4818) or in the period from 2003 to 2012 (KiGGS Wave 1, n = 4434). Determination of social status was based on parental educational levels, occupational position and income. Children classified as having a two-sided migration background either had parents, both of whom had immigrated to Germany, or were born abroad and had one parent who had immigrated to Germany; children classified as having a one-sided migration background had been born in Germany but had one parent who had immigrated to Germany. Results: The percentage of children whose mothers had smoked during pregnancy was 19.9 % for the older birth cohort and 12.1 % for the younger birth cohort. In both birth cohorts, the probability of being exposed to tobacco smoke was twice as high for children whose mothers were aged < 25 years at delivery compared to the children of older mothers. Children from socially deprived families were most affected by smoking behavior, and the relative social differences were found to have even increased over time (KiGGS baseline study: OR = 6.34; 95 % CI = 4.53-8.86; KiGGS Wave 1: OR = 13.88; 95 % CI = 6.85-28.13). A two-sided migration background was associated with a lower risk of exposure to smoking. Conclusions: The KiGGS results are in accordance with the results of other national and international studies which have shown that the percentage of mothers who smoke during pregnancy is declining. Because of a change in the method how data are collected for the KiGGS survey (written questionnaire vs. telephone interview) the trend results must be interpreted with caution. Measures aimed at preventing smoking and weaning women off smoking should focus particularly on younger and socially deprived mothers.

Promising candidates for allergy prevention

Recent advances in understanding environmental risk factors for allergic diseases in children have led to renewed efforts aimed at prevention. Factors that modify the probability of developing allergies include prenatal exposures, mode of delivery, diet, patterns of medication use, and exposure to pets and farm animals. Recent advances in microbial detection techniques demonstrate that exposure to diverse microbial communities in early life is associated with a reduction in allergic disease. In fact, microbes and their metabolic products might be essential for normal immune development. Identification of these risk factors has provided new targets for prevention of allergic diseases, and possibilities of altering microbial exposure and colonization to reduce the incidence of allergies is a promising approach. This review examines the rationale, feasibility, and potential effect for the prevention of childhood allergic diseases and explores possible strategies for enhancing exposure to beneficial microbes.

Breastfeeding is protective to diabetes risk in young adults: a longitudinal study

AIM

It is unclear whether any breastfeeding or a certain duration of breastfeeding is protective against the development of diabetes in adult offspring.

METHODS

We followed a sub-sample of 3,595 offspring born in the Mater Hospital in Brisbane, Australia between 1981 and 1983 and for whom we had doctor diagnosed self-reported diabetes at age 21 years and maternal reported duration of breastfeeding at 6-month post-natal follow-up. Multiple logistic regression was used to examine the independent associations of duration of breastfeeding (never breastfeed, breastfed <4 months and breastfed ≥4 months) with offspring diabetes by age 21 years.

RESULTS

Of 3,595 young adults, 45 (1.25 %) developed diabetes by age 21 years. The odds ratio of experiencing diabetes was 0.58 (95 % CI 0.29, 1.16) for offspring who were breastfed <4 months, and it was 0.29 (95 % CI 0.13, 0.63), for offspring who were breastfed at least 4 months compared to the never breastfed offspring. Adjusting for potential confounding and mediating factors including maternal age, education, pre-pregnancy body mass index (BMI), smoking, offspring sports, TV and their BMI at 21 years did not substantially alter this association.

CONCLUSIONS

Findings of this study suggest that infants who are breastfed for longer than 4 months have a substantial protective effect against the development of diabetes in young adulthood, which is independent of current BMI. Promoting breastfeeding for a minimum of 4 months may be a useful strategy for the prevention of diabetes among young adults.

Impact of childhood anthropometry trends on adult lung function

BACKGROUND

Poor fetal growth rate is associated with lower respiratory function; however, there is limited understanding of the impact of growth trends and BMI during childhood on adult respiratory function.

METHODS

The current study data are from the Mater-University of Queensland Study of Pregnancy birth cohort. Prospective data were available from 1,740 young adults who performed standard spirometry at 21 years of age and whose birth weight and weight, height, and BMI at 5, 14, and 21 years of age were available. Catch-up growth was defined as an increase of 0.67 Z score in weight between measurements. The impact of catch-up growth on adult lung function and the relationship between childhood BMI trends and adult lung function were assessed using regression analyses.

RESULTS

Lung function was higher at 21 years in those demonstrating catch-up growth from birth to 5 years (FVC, men: 5.33 L vs 5.54 L; women: 3.78 L vs 4.03 L; and FEV1, men: 4.52 L/s vs 4.64 L/s; women: 3.31 L/s vs 3.45 L/s). Subjects in the lowest quintile of birth (intrauterine growth retardation) also showed improved lung function if they had catch-up growth in the first 5 years of life. There was a positive correlation between increasing BMI and lung function at 5 years of age. However, in the later measurements when BMI increased into the obese category, a drop in lung function was observed.

CONCLUSIONS

These data show evidence for a positive contribution of catch-up growth in early life to adult lung function. However, if weight gain or onset of obesity occurs after 5 years of age, an adverse impact on adult lung function is noted.

Smoke exposure, wheezing, and asthma development: a systematic review and meta-analysis in unselected birth cohorts

BACKGROUND

The understanding of the role of smoking exposure in the induction of wheezing and asthma in children is important for prevention.

METHODS

A systematic review of literature and a meta-analysis were conducted to identify studies on unselected prospective birth cohorts. The effect of exposure to maternal/parental smoking on the induction of current wheezing or asthma was evaluated in children aged 6 months, <6 years, and ≥6 years. Pooled odds ratios (OR) with 95% confidence intervals (CI) were estimated.

RESULTS

We identified 43 papers. Exposure to maternal prenatal smoking was associated with an increased risk of wheezing in <6-year-olds (OR 1.36; 95% CI: 1.19-1.55) and of wheezing or asthma in ≥6-year-olds (OR: 1.22, 95% CI: 1.03-1.44). A positive association (OR: 1.24, 95% CI: 1.11-1.38) was also found in the only three studies that evaluated exposure to maternal prenatal smoking alone. Postnatal exposures to maternal/parental smoking were associated with wheezing in <6-year-olds (OR: 1.21; 95% CI: 1.13-1.31 and OR: 1.30; 95% CI: 1.13-1.51), although it was often impossible to separate the role of postnatal from that of prenatal exposure; data in schoolchildren are limited and this precluded a meta-analysis. No clear association was found between exclusive postnatal exposure and wheezing or asthma.

CONCLUSIONS

We confirmed an important role of prenatal exposure to maternal smoking on the induction of wheezing and asthma in offspring, particularly in the first years of life. More studies with a consistent number of subjects only exposed to smoke postnatally are needed to better investigate the harmful effects on the induction of wheezing or asthma, particularly in schoolchildren.

Epigenetic contributions to the developmental origins of adult lung disease

Perinatal insults, including intrauterine growth restriction, preterm birth, maternal exposure to toxins, or dietary deficiencies produce deviations in the epigenome of lung cells. Occurrence of perinatal insults often coincides with the final stages of lung development. The result of epigenome disruptions in response to perinatal insults during lung development may be long-term structural and functional impairment of the lung and development of lung disease. Understanding the contribution of epigenetic mechanisms to life-long lung disease following perinatal insults is the focus of the developmental origins of adult lung disease field. DNA methylation, histone modifications, and microRNA changes are all observed in various forms of lung disease. However, the perinatal contribution to such epigenetic mechanisms is poorly understood. Here we discuss the developmental origins of adult lung disease, the interplay between perinatal events, lung development and disease, and the role that epigenetic mechanisms play in connecting these events.

Maternal and paternal indoor or outdoor smoking and the risk of asthma in their children: a nationwide prospective birth cohort study

BACKGROUND

Little is known about the differential impact of combinations of parental smoking behavior (indoor or outdoor smoking, or not smoking) on preventing childhood asthma. Our objective was to examine the association between parental smoking behavior and children's asthma.

METHODS

A nationally representative population-based birth cohort of 40,580 babies, aged 0.5 years in 2001 (response rate, 87.8%), was studied to estimate adjusted odds ratios of combinations of maternal and paternal indoor or outdoor smoking at home for physician visits and hospitalization for childhood asthma up to 8-years-old, and population attributable fractions.

RESULTS

Odds of hospitalization for asthma among children whose father alone smokes indoors at home did not largely increase (up to 20%). However, if the mother also smokes indoors at home, the odds strongly increased. After adjusting for demographic, perinatal and socioeconomic factors, the increase in odds for children whose father and mother both smoke indoors compared to children with non-smoking parents was 54% (95% confidence interval: 21-96%), 43% (8-90%) and 72% (22-143%) for children aged 0.5<-2.5, 2.5<-4.5 and 4.5<-8 years-old, respectively. The odds ratios of smoking outdoors did not largely differ from those of smoking indoors. Our estimation of population attributable fractions revealed that if all parents in Japan quit smoking, hospitalization of children for asthma could be reduced by 8.3% (2.2-14.3%), 9.3% (0.9-17.6%) and 18.2% (7.7-28.8%), respectively.

CONCLUSIONS

Parental indoor smoking at home increased and exacerbated children's asthma. Smoking at home, whether it is indoors or outdoors, may increase the risks for asthma attacks of their children.

Nuclear and mitochondrial DNA alterations in newborns with prenatal exposure to cigarette smoke

Newborns exposed to maternal cigarette smoke (CS) in utero have an increased risk of developing chronic diseases, cancer, and acquiring decreased cognitive function in adulthood. Although the literature reports many deleterious effects associated with maternal cigarette smoking on the fetus, the molecular alterations and mechanisms of action are not yet clear. Smoking may act directly on nuclear DNA by inducing mutations or epigenetic modifications. Recent studies also indicate that smoking may act on mitochondrial DNA by inducing a change in the number of copies to make up for the damage caused by smoking on the respiratory chain and lack of energy. In addition, individual genetic susceptibility plays a significant role in determining the effects of smoking during development. Furthermore, prior exposure of paternal and maternal gametes to cigarette smoke may affect the health of the developing individual, not only the in utero exposure. This review examines the genetic and epigenetic alterations in nuclear and mitochondrial DNA associated with smoke exposure during the most sensitive periods of development (prior to conception, prenatal and early postnatal) and assesses how such changes may have consequences for both fetal growth and development.

Effect of a family-centered, secondhand smoke intervention to reduce respiratory illness in indigenous infants in Australia and New Zealand: a randomized controlled trial

INTRODUCTION

Secondhand smoke (SHS) is a significant cause of acute respiratory illness (ARI) and 5 times more common in indigenous children. A single-blind randomized trial was undertaken to determine the efficacy of a family centered SHS intervention to reduce ARI in indigenous infants in Australia and New Zealand.

METHODS

Indigenous mothers/infants from homes with ≥ 1 smoker were randomized to a SHS intervention involving 3 home visits in the first 3 months of the infants' lives (plus usual care) or usual care. The primary outcome was number of ARI-related visits to a health provider in the first year of life. Secondary outcomes, assessed at 4 and 12 months of age, included ARI hospitalization rates and mothers' report of infants' SHS exposure (validated by urinary cotinine/creatinine ratios [CCRs]), smoking restrictions, and smoking cessation.

RESULTS

Two hundred and ninety-three mother/infant dyads were randomized and followed up. Three quarters of mothers smoked during pregnancy and two thirds were smoking at baseline (as were their partners), with no change for more than 12 months. Reported infant exposure to SHS was low (≥ 95% had smoke-free homes/cars). Infant CCRs were higher if one or both parents were smokers and if mothers breast fed their infants. There was no effect of the intervention on ARI events [471 intervention vs. 438 usual care (reference); incidence rate ratio = 1.10, 95% confidence intervals (CI) = 0.88-1.37, p = .40].

CONCLUSIONS

Despite reporting smoke-free homes/cars, mothers and their partners continue to smoke in the first year of infants' lives, exposing them to SHS. Emphasis needs to be placed on supporting parents to stop smoking preconception, during pregnancy, and postnatal.

Cohort Profile Update: The Mater-University of Queensland Study of Pregnancy (MUSP)

The Mater-University of Queensland Study of Pregnancy (MUSP) and its outcomes began in 1981 with data collected on 7223 pregnant woman-child pairs (6753 mothers, of whom 520 had 2 study children, less 50 who had multiple births). These women, and their children, were initially followed for up to 21 years. Since then there have been additional follow-ups of the mothers (27 years) and their children (30 years). There has also been a substantial increase in the breadth of topics addressed, with the collection of biological samples, the administration of structured clinical assessments of mental health and cognitive capacity, and markers of physical health such as lung function and blood pressure. MUSP was originally developed as a birth cohort study. It has become a longitudinal study of growth, development and ageing with an emphasis on the generational transmission of a wide range of factors impacting on adult health outcomes. We welcome interest in our study; for study background and publications visit [www.socialscience.uq.edu.au/musp] or contact [j.najman@uq.edu.au].

Early life environmental predictors of asthma age-of-onset

Prevention strategies that delay the onset of asthma may improve clinical outcomes. To identify early life environmental exposures associated with asthma age-of-onset and potential genetic modifiers of these exposures, we studied 1085 subjects with physician-diagnosed asthma and disease onset at or after age two. Subjects reported retrospectively on their exposure to 17 environmental factors before the age of two. The presence of individual or combinations of these early life exposures was then tested for association with variation in asthma age-of-onset. For exposures significantly associated with age-of-onset, we tested if 26 single nucleotide polymorphisms (SNP) with an established association with allergic disease significantly modified the effect of the exposure. Five environmental exposures were significantly associated with variation in asthma age-of-onset after correction for multiple testing: carpet at home (P = 6 × 10⁻⁵), a serious chest illness (P = 10⁻⁴), father a cigarette smoker (P = 6 × 10⁻⁴) and direct exposure to father's smoking (P = 3 × 10⁻⁴). Individuals with early childhood asthma onset, between the ages of two and six, were 1.4-fold (CI 1.1–1.9) more likely to report having lived in a house with carpet and 2.1-fold (CI 1.3–3.5) more likely to report suffering a serious chest illness before the age of two, than asthmatics with later disease onset. We further found these individual risks to increase to 3.2-fold (CI 1.7–6.0) if carpet exposure and suffering a serious chest illness co-occurred before age two. Paternal smoking exposures were less likely to be reported by asthmatics with early when compared to later disease onset (OR 0.5, CI 0.3–0.7). There were no significant SNP interactions with these environmental exposures after correction for multiple testing. Our results suggest that disease onset in individuals at a high-risk of developing asthma can potentially be delayed by avoiding exposure to carpet at home and preventing serious chest illnesses during the first 2 years of life.

Maternal pregravid body mass index and child hospital admissions in the first 5 years of life: results from an Australian birth cohort

OBJECTIVES

To examine the association of maternal pregravid body mass index (BMI) and child offspring, all-cause hospitalisations in the first 5 years of life.

METHODS

Prospective birth cohort study. From 2006 to 2011, 2779 pregnant women (2807 children) were enrolled in the Environments for Healthy Living: Griffith birth cohort study in South-East Queensland, Australia. Hospital delivery record and self-report baseline survey of maternal, household and demographic factors during pregnancy were linked to the Queensland Hospital Admitted Patients Data Collection from 1 November 2006 to 30 June 2012, for child admissions. Maternal pregravid BMI was classified as underweight (<18.5 kg m(-)(2)), normal weight (18.5-24.9 kg m(-)(2)), overweight (25.0-29.9 kg m(-)(2)) or obese (⩾30 kg m(-)(2)). Main outcomes were the total number of child hospital admissions and ICD-10-AM diagnostic groupings in the first 5 years of life. Negative binomial regression models were calculated, adjusting for follow-up duration, demographic and health factors. The cohort comprised 8397.9 person years (PYs) follow-up.

RESULTS

Children of mothers who were classified as obese had an increased risk of all-cause hospital admissions in the first 5 years of life than the children of mothers with a normal BMI (adjusted rate ratio (RR) =1.48, 95% confidence interval 1.10-1.98). Conditions of the nervous system, infections, metabolic conditions, perinatal conditions, injuries and respiratory conditions were excessive, in both absolute and relative terms, for children of obese mothers, with RRs ranging from 1.3-4.0 (PYs adjusted). Children of mothers who were underweight were 1.8 times more likely to sustain an injury or poisoning than children of normal-weight mothers (PYs adjusted).

CONCLUSION

RESULTS suggest that if the intergenerational impact of maternal obesity (and similarly issues related to underweight) could be addressed, a significant reduction in child health care use, costs and public health burden would be likely.

Prevention of asthma: where are we in the 21st century?

Asthma is the most common chronic disease of childhood and, in the latter part of the 20th century, reached epidemic proportions. Asthma is generally believed to result from gene-environment interactions. There is consensus that a 'window of opportunity' exists during pregnancy and early in life when environmental factors may influence its development. We review multiple environmental, biologic and sociologic factors that may be important in the development of asthma. Meta-analyses of studies have demonstrated that multifaceted interventions are required in order to develop asthma prevention. Multifaceted allergen reduction studies have shown clinical benefits. Asthma represents a dysfunctional interaction with our genes and the environment to which they are exposed, especially in fetal and early infant life. The increasing prevalence of asthma also may be an indication of increased population risk for the development of other chronic non-communicable autoimmune diseases. This review will focus on the factors which may be important in the primary prevention of asthma. Better understanding of the complex gene-environment interactions involved in the development of asthma will provide insight into personalized interventions for asthma prevention.

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

RATIONALE

The extent to which maternal smoking in pregnancy (MSP) has persisting effects on respiratory health remains uncertain and the mechanisms involved are not fully understood. Alterations in immune function have been proposed as a mechanism contributing to respiratory disease.

OBJECTIVES

To determine whether MSP increases risk of respiratory disorders in adolescence and, if so, whether this occurs by decreased lung function, altered immune function, and/or enhanced atopy.

METHODS

Data on spirometry, bronchial responsiveness, respiratory symptoms, total and allergen-specific IgE and IgG4, immune function, and inflammatory markers were obtained from 1,129 participants in the 14-year follow-up of the Western Australian Pregnancy (Raine) Cohort and related to MSP using regression analyses.

MEASUREMENTS AND MAIN RESULTS

MSP was reported for 21.0% (237 of 1,129) of participants, with 92 (8.1%) reporting current smoking. MSP was associated with some altered immune measures at age 14. MSP was strongly related to reduced lung function in current nonsmokers (forced expiratory flow midexpiratory phase [FEF25-75%], P = 0.016; FEV1/FVC, P = 0.009) and increased risk for current asthma (odds ratio [OR], 1.84; 95% confidence interval [CI], 1.16-2.92; P = 0.01), current wheeze (OR, 1.77; 95% CI, 1.14-2.75; P = 0.011), and exercise-induced wheeze (OR, 2.29; 95% CI, 1.37-3.85; P = 0.002), but not for bronchial hyperresponsiveness or atopy. Adjustment for immune measures and/or lung function in multivariate models did not greatly alter these associations and the increased risks for asthma and wheeze were not modified by sex, atopy, or maternal history of asthma or atopy.

CONCLUSIONS

MSP increases risk of asthma and wheezing in adolescence; mechanisms go beyond reducing lung function and exclude altering immune function or enhancing atopy.

Effects of tobacco smoke exposure in childhood on atopic diseases

Although the smoking prevalence in the United States continues to decline since the Surgeon General's first report in 1964, certain vulnerable populations continue to be disproportionately affected by the adverse consequences of tobacco smoke exposure. Children are particularly vulnerable to exposure and are likely to suffer from both short- and long-term adverse consequences after early life tobacco smoke exposure. An overwhelming amount of evidence supports an association between asthma development and tobacco smoke exposure, and evidence is mounting that tobacco smoke exposure may also increase risk of IgE sensitization. This manuscript will review the effects of tobacco smoke exposure in childhood on the development of asthma and allergic sensitization, and will review practical strategies to assist motivated parents with smoking cessation.

Epigenetic regulation in allergic diseases and related studies

Asthma, a chronic inflammatory disorder of the airway, has features of both heritability as well as environmental influences which can be introduced in utero exposures and modified through aging, and the features may attribute to epigenetic regulation. Epigenetic regulation explains the association between early prenatal maternal smoking and later asthma-related outcomes. Epigenetic marks (DNA methylation, modifications of histone tails or noncoding RNAs) work with other components of the cellular regulatory machinery to control the levels of expressed genes, and several allergy- and asthma-related genes have been found to be susceptible to epigenetic regulation, including genes important to T-effector pathways (IFN-γ, interleukin [IL] 4, IL-13, IL-17) and T-regulatory pathways (FoxP3). Therefore, the mechanism by which epigenetic regulation contributes to allergic diseases is a critical issue. In the past most published experimental work, with few exceptions, has only comprised small observational studies and models in cell systems and animals. However, very recently exciting and elegant experimental studies and novel translational research works were published with new and advanced technologies investigating epigenetic mark on a genomic scale and comprehensive approaches to data analysis. Interestingly, a potential link between exposure to environmental pollutants and the occurrence of allergic diseases is revealed recently, particular in developed and industrialized countries, and endocrine disrupting chemicals (EDCs) as environmental hormone may play a key role. This review addresses the important question of how EDCs (nonylphenol, 4 octylphenol, and phthalates) influences on asthma-related gene expression via epigenetic regulation in immune cells, and how anti-asthmatic agents prohibit expression of inflammatory genes via epigenetic modification. The discovery and validation of epigenetic biomarkers linking exposure to allergic diseases might lead to better epigenotyping of risk, prognosis, treatment prediction, and development of novel therapies.

Potential risk of asthma associated with in utero exposure to xenobiotics

The incidence of asthma, a complex disease and significant public health problem, has been increasing over the last 30 years for unknown reasons. Changes in environmental exposures or lifestyle may be involved. In some cases asthma may originate in utero or in early life. Associations have been found between in utero exposures to several xenobiotics and increased risk of asthma. There is convincing evidence that maternal smoking and/or in utero and perinatal exposure to environmental tobacco smoke are associated with increased risk of asthma. Similar effects have been demonstrated in animal models of allergic asthma. Evidence also suggests that in utero and/or early-life exposures to various ambient air pollutants may increase the risk of asthma although supporting animal data are very limited. A few studies have suggested that in utero exposure to acetaminophen is associated with increased risk of asthma; however, animal data are lacking. Various vitamin deficiencies and supplements during pregnancy have been studied. In general, it appears that vitamins A, C, and E have protective effects and vitamins D and B may, in some instances, increase the risk, but the data are not conclusive. Some studies related to in utero exposures to polychlorinated biphenyls and bisphenol A and asthma risk are also reported. The underlying mechanisms for an association between xenobiotic exposures and asthma remain a matter of speculation. Genetic predisposition and epigenetic changes have been explored. The developing immune, respiratory, and nervous systems are potential targets. Oxidative stress and modulation of inflammation are thought to be involved.

From Childhood Asthma to Chronic Obstructive Pulmonary Disease: Evidence Supporting a Disease Continuum

In this review, we analyze the available evidence showing a link between asthma and chronic obstructive pulmonary disease (COPD). Many features (epidemiologic, physiologic, and histologic) overlap between these two conditions. Both environmental cigarette smoke exposure and early lung development are risk factors for the development of asthma and COPD. However, recent studies suggest that up to 25% of COPD cases were nonsmokers. Asthma during early childhood, independent of smoking history, may be an independent risk factor for the later development of COPD. One explanation for this phenomenon suggests that early small airway dysfunction (including chronic airway inflammation and airway remodeling) can lead to permanent impairment in lung physiology. Several reasons why control of airway inflammation is difficult in some patients are explored. Finally, we examine the available evidence suggesting overlapping histologic features in both asthma and COPD.

Prenatal smoke exposure, DNA methylation, and childhood atopic dermatitis

BACKGROUND

The biological mechanisms of how prenatal smoke exposure leading to atopic disorders remain to be addressed. Whether prenatal smoke exposure affects DNA methylation leading to atopic disorders is not clear.

OBJECTIVE

As most children suffering from atopic dermatitis (AD) continue to develop asthma later in life, we explored whether prenatal smoke exposure induces cord blood DNA methylation.

METHODS

Methylation differences associated with smoke exposure were screened by Illumina Infinium 27K methylation arrays for 14 children from the Taiwan birth panel study cohort initially. Information about development of atopic dermatitis (AD) and risk factors was collected. Cord blood cotinine levels were measured to represent prenatal smoke exposure. CpG loci that demonstrated a statistically significant difference in methylation were validated by methylation-dependent fragment separation (MDFS). Differential methylation in three genes (TSLP, GSTT1, and CYB5R3) was identified through the screen.

RESULTS

Among these, only thymic stromal lymphopoietin (TSLP) gene displayed significant difference in promoter methylation percentage after being validated by MDFS (p = 0.018). TSLP gene was further investigated in a larger sample of 150 children from the cohort who completed the follow-up study. Methylation status of the TSLP 5'-CpG island (CGI) was found to be significantly associated with prenatal smoke exposure (OR = 3.17, 95% CI = 1.63-6.19) and with AD (OR = 2.32, 95% CI = 1.06-5.11). The degree of TSLP 5'CGI methylation inversely correlated with TSLP protein expression levels (r = -0.45, P = 0.001).

CONCLUSIONS & CLINICAL RELEVANCE

The effect of prenatal tobacco smoke exposure on the risk for AD may be mediated through DNA methylation.

Tobacco or healthy children: the two cannot co-exist

Tobacco exposure increases mortality and morbidity of the fetus, the child, the adolescent, and their children in turn. Nearly half the children in the world are exposed. Smoking is not merely personal choice or personal responsibility; those subtle phrases undermine those who have no choice in the matter. Tobacco control must take a multi-pronged attack. Smoking cessation by adults in childbearing years must take center stage of these efforts, because it is the only way to ensure a smoke-free environment for children. Smoke-free parents provide a role model for smoke-free young people, and erode the image of smoking as a desirable adult behavior to emulate. Pediatricians and pediatric pulmonologists have a key role to play here. This goal will reduce morbidity and mortality among adults and children. Legislation regarding taxation, environments, tobacco constituents, product placement and display, packaging, and media education are all key to this core goal. Smoke-free policy must be protected from attack based on trade agreements. Research is needed into more effective ways to attract and help people give up smoking, and into educating and re-deploying tobacco industry workers in emerging and developed countries.

Meta-analysis of the association between secondhand smoke exposure and physician-diagnosed childhood asthma

INTRODUCTION

Studies suggest an association between secondhand smoke exposure and the development of childhood asthma. Several countries are considering legislation to protect children from exposure.

METHODS

A systematic review was conducted using MEDLINE, Embase, PubMed, and Web of Knowledge databases and a random effects meta-analysis was undertaken. Heterogeneity was assessed using the I (2) test. Publication and small study biases were examined visually using a funnel plot and tested formally using Egger test. Univariate and multivariate meta-regression analyses were undertaken, including a subgroup analysis of cohort studies to examine the effect of duration of follow-up.

RESULTS

Twenty relevant studies were identified (14 cross-sectional, 4 cohort, and 2 case-control) and provided 31 estimates of effect size. The pooled odds ratio was 1.32 (95% CI: 1.23, 1.42, p < .001). There was moderate heterogeneity (I (2) = 74.2%, p < .001). On multivariate meta-regression analysis, effect size estimates were significantly higher for case-control studies (p = .042) and those using self-reported exposure to secondhand smoke (p = .050). There was no evidence of significant publication or small study bias (Egger test, p = .121).

CONCLUSIONS

There is now consistent evidence of a modest association between secondhand smoke and physician-diagnosed childhood asthma. These results lend support to continued efforts to reduce childhood exposure to secondhand smoke.

Environments for Healthy Living (EFHL) Griffith birth cohort study: background and methods

The health of an individual is determined by the interaction of genetic and individual factors with wider social and environmental elements. Public health approaches to improving the health of disadvantaged populations will be most effective if they optimise influences at each of these levels, particularly in the early part of the life course. In order to better ascertain the relative contribution of these multi-level determinants there is a need for robust studies, longitudinal and prospective in nature, that examine individual, familial, social and environmental exposures. This paper describes the study background and methods, as it has been implemented in an Australian birth cohort study, Environments for Healthy Living (EFHL): The Griffith Study of Population Health. EFHL is a prospective, multi-level, multi-year longitudinal birth cohort study, designed to collect information from before birth through to adulthood across a spectrum of eco-epidemiological factors, including genetic material from cord-blood samples at birth, individual and familial factors, to spatial data on the living environment. EFHL commenced the pilot phase of recruitment in 2006 and open recruitment in 2007, with a target sample size of 4000 mother/infant dyads. Detailed information on each participant is obtained at birth, 12-months, 3-years, 5-years and subsequent three to five yearly intervals. The findings of this research will provide detailed evidence on the relative contribution of multi-level determinants of health, which can be used to inform social policy and intervention strategies that will facilitate healthy behaviours and choices across sub-populations.

Asthma and mental health among youth: etiology, current knowledge and future directions

Asthma and mental health problems, such as depression, anxiety and behavior disorders, are common among youth and are significant sources of morbidity. There is a consistent association between asthma and anxiety/depression and a less consistent association between asthma and behavior disorders. Possible biological and psychological mechanisms may include inflammatory processes as well as the stress of having to live with a life-threatening condition. Future studies are warranted with longitudinal designs to establish temporality as well as measures of potential confounds. Biological and psychological measures would complement the longitudinal design to further establish causality. In addition, more information on the degree to which asthma and mental health have reciprocal influences on each other over time - and the mechanisms of these relationships - are needed in order to develop more effective intervention strategies to improve asthma control and mental health among those with both.

Maternal occupational exposure to asthmogens during pregnancy and risk of asthma in 7-year-old children: a cohort study

OBJECTIVES

The objective of this study was to examine whether maternal exposure to asthmogens during pregnancy is associated with the development of asthma in 7-year-old Danish children, taking atopic status and sex into consideration.

DESIGN

The study is a prospective follow-up of a birth cohort.

SETTING AND PARTICIPANTS

A total of 41 724 women and their children from The Danish National Birth Cohort were categorised according to maternal occupational exposure. Exposure information was obtained by combining job title in pregnancy and 18 months after pregnancy with a commonly used asthma Job Exposure Matrix.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcome was parent-reported asthma among their 7-year-old children in an internet-based questionnaire. Secondary outcome was asthma among the same children with or without atopic dermatitis and among boys and girls, respectively.

RESULTS

Prenatal exposure to low molecular weight (LMW) agents was borderline associated with asthma in children with OR 1.17 (0.95 to 1.44) for children with atopic dermatitis and 1.10 (0.98 to 1.22) for children without. Maternal postnatal exposure was associated with asthma (OR 1.15 (1.04 to 1.28). After mutual adjustment,postnatal exposure (OR 1.13 (0.99 to 1.29) and the combined effects of prenatal and postnatal exposure (OR 1.34 (1.19 to 1.51)) seem to increase the risk of asthma in children. No significant associations were observed for other prenatal or postnatal exposures. The gender of the child did not modify the aforementioned associations.

CONCLUSIONS

Maternal occupational exposures during pregnancy do not seem to be a substantial risk factor for the development of asthma in 7-year-old children. Maternal prenatal and postnatal exposures to LMW agents may predispose the propensity of the children to develop asthma. Future studies should prioritise the characterisation of the timing of exposure in relation to the birth.

Effects of fetal exposure to urban particulate matter on the immune system of male mouse offspring

Urban particulate matter (UPM) has been shown to have an aggravating effect on Th2-associated immune systems in adult mice. However, the effects of fetal exposure to UPM on immune response in offspring have not been elucidated. In the present study, we administered UPM (200 µg/animal) by intratracheal injection to pregnant dams on days 7 and 14 of gestation. Subsequently, 9- and 24-week-old male offspring were intratracheally injected with ovalbumin (OVA) (four times at 2-week intervals) to create a mouse model of bronchial asthma. We then evaluated the progression of allergic manifestations in the offspring through histological findings, the number of inflammatory cells in bronchoalveolar lavage fluid (BALF), and protein concentration of cytokines and chemokines in BALF 5, 10, 15, and 30 weeks after birth. Histological examination showed that fetal exposure to UPM alone caused slight eosinophil and lymphocyte infiltration in the submucosa of the airway and bronchial epithelium and significant increases in the number of macrophages. Moreover, postnatal intratracheal administration of OVA to offspring exposed to UPM in utero caused significant increases in the numbers of macrophages, eosinophils, and lymphocytes and in the concentrations of their relevant cytokines and chemokines, showing that fetal exposure to UPM aggravated the chemically sensitized immune system of male offspring.

Developmental trajectories of body mass index among Japanese children and impact of maternal factors during pregnancy

Background

The aims of this study were to 1) determine the distinct patterns of body mass index (BMI) trajectories in Japanese children, and 2) elucidate the maternal factors during pregnancy, which contribute to the determination of those patterns.

Methodology/Principal Findings

All of the children (1,644 individuals) born in Koshu City, Japan, between 1991 and 1998 were followed in a longitudinal study exploring the subjects’ BMI. The BMI was calculated 11 times for each child between birth and 12 years of age. Exploratory latent class growth analyses were conducted to identify trajectory patterns of the BMI z-scores. The distribution of BMI trajectories were best characterized by a five-group model for boys and a six-group model for girls. The groups were named “stable thin,” “stable average,” “stable high average,” “progressive overweight,” and “progressive obesity” in both sexes; girls were allocated to an additional group called “progressive average.” Multinomial logistic regression found that maternal weight, smoking, and skipping breakfast during pregnancy were associated with children included in the progressive obesity pattern rather than the stable average pattern. These associations were stronger for boys than for girls.

Conclusions/Significance

Multiple developmental patterns in Japanese boys and girls were identified, some of which have not been identified in Western countries. Maternal BMI and some unfavorable behaviors during early pregnancy may impact a child’s pattern of body mass development. Further studies to explain the gender and regional differences that were identified are warranted, as these may be important for early life prevention of weight-associated health problems.

Street drug use during pregnancy: potential programming effects on preschool wheeze

Street drug use during pregnancy is detrimental to fetal development. Although the prevalence of wheeze is high in offspring of substance-abusing mothers, nothing is known about the role of street drug use during pregnancy in its development. We investigated the impact of maternal street drug use and distress during pregnancy on the development of wheeze and allergy in preschool children. Questionnaire data were accessed from the Community Perinatal Care trial of 791 mother–child pairs in Calgary, Alberta. Using logistic regression, the association between maternal substance use and distress during pregnancy, and wheeze and allergy at age 3 years was determined in boys and girls. After adjusting for alcohol use during pregnancy, pre- and postnatal tobacco use, preterm birth, duration of exclusive breastfeeding, daycare attendance and maternal socioeconomic status, maternal street drug use during pregnancy [odds ratio (OR): 5.02, 95% confidence interval (CI): 1.30–19.4] and severe maternal distress during pregnancy (OR: 5.79, 95% CI: 1.25–26.8) were associated with wheeze in girls. In boys, an independent association was found between severe distress during pregnancy (OR: 3.85, 95% CI: 1.11–13.3) and allergies, but there was no association with maternal street drug use. In conclusion, we found an association between maternal street drug use and wheeze in preschool girls that could not be accounted for by maternal distress, smoking or alcohol use during pregnancy. Prenatal programming effects of street drugs may explain this association.

Perinatal nicotine exposure induces asthma in second generation offspring

BACKGROUND

By altering specific developmental signaling pathways that are necessary for fetal lung development, perinatal nicotine exposure affects lung growth and differentiation, resulting in the offsprings' predisposition to childhood asthma; peroxisome proliferator-activated receptor gamma (PPARγ) agonists can inhibit this effect. However, whether the perinatal nicotine-induced asthma risk is restricted to nicotine-exposed offspring only; whether it can be transmitted to the next generation; and whether PPARγ agonists would have any effect on this process are not known.

METHODS

Time-mated Sprague Dawley rat dams received either placebo or nicotine (1 mg/kg, s.c.), once daily from day 6 of gestation to postnatal day (PND) 21. Following delivery, at PND21, generation 1 (F1) pups were either subjected to pulmonary function tests, or killed to obtain their lungs, tracheas, and gonads to determine the relevant protein markers (mesenchymal contractile proteins), global DNA methylation, histone 3 and 4 acetylation, and for tracheal tension studies. Some F1 animals were used as breeders to generate F2 pups, but without any exposure to nicotine in the F1 pregnancy. At PND21, F2 pups underwent studies similar to those performed on F1 pups.

RESULTS

Consistent with the asthma phenotype, nicotine affected lung function in both male and female F1 and F2 offspring (maximal 250% increase in total respiratory system resistance, and 84% maximal decrease in dynamic compliance following methacholine challenge; P < 0.01, nicotine versus control; P < 0.05, males versus females; and P > 0.05, F1 versus F2), but only affected tracheal constriction in males (51% maximal increase in tracheal constriction following acetylcholine challenge, P < 0.01, nicotine versus control; P < 0.0001, males versus females; P > 0.05, F1 versus F2); nicotine also increased the contractile protein content of whole lung (180% increase in fibronectin protein levels, P < 0.01, nicotine versus control, and P < 0.05, males versus females) and isolated lung fibroblasts (for example, 45% increase in fibronectin protein levels, P < 0.05, nicotine versus control), along with decreased PPARγ expression (30% decrease, P < 0.05, nicotine versus control), but only affected contractile proteins in the male trachea (P < 0.05, nicotine versus control, and P < 0.0001, males versus females). All of the nicotine-induced changes in the lung and gonad DNA methylation and histone 3 and 4 acetylation were normalized by the PPARγ agonist rosiglitazone except for the histone 4 acetylation in the lung.

CONCLUSIONS

Germline epigenetic marks imposed by exposure to nicotine during pregnancy can become permanently programmed and transferred through the germline to subsequent generations, a ground-breaking finding that shifts the current asthma paradigm, opening up many new avenues to explore.

Sex-specific perinatal nicotine-induced asthma in rat offspring

Recently, we have suggested that down-regulation of homeostatic mesenchymal peroxisome proliferator-activated receptor γ signaling after in utero nicotine exposure might contribute to asthma. Here, we have exploited an in vivo rat model of asthma to determine if the effects of perinatal nicotine exposure on offspring pulmonary function and mesenchymal markers of airway contractility in both tracheal and lung parenchymal tissue are sex specific, and whether the protection afforded by the peroxisome proliferator-activated receptor γ agonist, rosiglitazone (RGZ), against the perinatal nicotine-induced effect on offspring lung is also sex specific. Pregnant rat dams received placebo, nicotine, or nicotine plus RGZ daily from Embryonic Day 6 until Postnatal Day 21, at which time lung resistance, compliance, tracheal contractility, and the expression of structural and functional mesenchymal markers of pulmonary contractility were determined. Compared with control animals, perinatal nicotine exposure caused a significant increase in airway resistance and a decrease in airway compliance after a methacholine challenge in both male and female offspring, with more pronounced changes in the males. In contrast to this, the effects of perinatal nicotine exposure on acetylcholine-induced tracheal constriction, along with the expression of its mesenchymal markers, were observed exclusively in the male offspring. Concomitant treatment with RGZ normalized the nicotine-induced alterations in pulmonary function in both sexes, as well as the male-specific effects on acetylcholine-induced tracheal constriction, along with the affected mesenchymal markers. These data suggest that perinatal nicotine exposure causes sex-specific perinatal cigarette smoke exposure-induced asthma, providing a powerful phenotypic model for unequivocally determining the underlying nature of the cell molecular mechanism for this disease.