Influence of smoking on asthmatic symptoms and allergen sensitisation in early childhood

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).

Association between prenatal or postpartum exposure to tobacco smoking and allergic rhinitis in the offspring: An updated meta-analysis of nine cohort studies

INTRODUCTION

Previous studies have suggested an association between tobacco smoke exposure and allergic rhinitis. This study aimed to investigate if prenatal or postpartum smoke exposure will increase the risk of allergic rhinitis in offspring.

METHODS

PubMed, EMBASE, and the Cochrane library were searched from inception to July 2020 for eligible studies investigating the association between smoking exposure and allergic rhinitis. The random-effects model was adopted for the meta-analysis to obtain the summary odds ratio (OR) with a 95% confidence interval (CI). Subgroup analysis based on the age of children was performed. Sensitivity analysis was carried out to check the robustness of the results. Publication bias of included studies was assessed.

RESULTS

This meta-analysis included nine studies, in which six studies suggested that children exposed to prenatal smoking were more likely to develop allergic rhinitis compared with children who were never exposed (OR=1.12; 95% CI: 1.04-1.21). The subgroup analysis divided children those aged <10 years (OR=1.15; 95% CI: 1.06-1.25) and those aged >10 years (OR=0.99; 95% CI: 0.82-1.20). This meta-analysis revealed a positive relationship between postpartum smoke exposure and the development of allergic rhinitis in offspring (OR=1.19; 95% CI: 1.03-1.39) with marked heterogeneity. The subgroup analysis of age in the postnatal group showed similar results in children aged >10 years (OR=1.17; 95% CI: 1.05-1.30) and children aged <10 years (OR=1.21; 95% CI: 0.91-1.60).

CONCLUSIONS

This meta-analysis observed an association between parental smoking exposure and allergic rhinitis in offspring. Our findings indicated that both prenatal and postnatal smoke exposure might be risk factors for allergic rhinitis in the offspring.

Association between active tobacco use during pregnancy and infant respiratory health: a systematic review and meta-analysis

OBJECTIVE

To evaluate what is known about active tobacco use during pregnancy and the association with infant respiratory health.

DESIGN

Systematic review and meta-analysis using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

DATA SOURCES

MEDLINE, EMBASE, Cochrane, CINAHL, and Maternity and Infant Care were searched thoroughly until June 2020.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

We included case-control and cohort studies estimating the association between active tobacco use during pregnancy and infant respiratory health (wheezing and apnoea) and lung function parameters in the first 12 months of life.

DATA EXTRACTION AND SYNTHESIS

Extraction and risk of bias assessment were conducted by two independent reviewers. The odds ratio, relative risk and mean differences were pooled with a 95% CI using the generic inverse variance method. Heterogeneity was assessed and expressed by percentage using I2.

RESULTS

We identified 4423 abstracts, and 21 publications met the eligibility criteria. Pooled OR showed an increase in wheezing episodes in infants born to mothers who were active tobacco users during pregnancy (OR 1.50, 95% CI 1.27 to 1.77, p<0.01). Mixed results were found on lung function parameters, and a meta-analysis including two studies with comparable methodology showed a trend towards reduced maximum flow rate at functional residual capacity of -34.59 mL/s (95% CI -72.81 to 3.63, p=0.08) in 1-month-old infants born to women who smoked during pregnancy. A higher risk of apnoea was described for infants born to mothers who used smokeless tobacco during pregnancy, while the results in infants born to women who actively smoked tobacco during pregnancy were non-conclusive.

CONCLUSION

Infants born to mothers who actively smoked during pregnancy are at higher odds of having wheeze and may have lower lung function. Smokeless tobacco use in pregnancy may increase the risk of apnoea in infancy.

PROSPERO REGISTRATION NUMBER

CRD42018083936.

Prevention of Allergic Asthma with Allergen Avoidance Measures and the Role of Exposome

PURPOSE OF REVIEW

It is well known that combination of sensitization and exposure to inhaled environmental allergens is related to both the development and elicitation of symptoms of asthma and that avoidance of allergens would exert beneficial effects in the prevention and control of the disease. Other important factors include the relevance of other allergens, exposure to sensitizing agents also outside patient's home, exposure to irritants (like chemical air pollutants), and the involvement of the patient with a correct education. It is also likely that clinical phase of allergic airway disease and the degree of airways remodeling represent relevant factors for the clinical outcome of allergen avoidance procedure. We reviewed existing evidence on prevention of asthma through allergen avoidance.

RECENT FINDINGS

The management of respiratory allergy is a complex strategy (including prevention, drugs, immunological, and educational interventions). In addition, it is difficult in real life to distinguish the efficacy of single interventions. However, a combined strategy is likely to produce clinical results. A combined strategy is likely to produce satisfactory management of asthma. Allergens are an important trigger factor for the development of symptoms of respiratory allergy, and avoidance measures are able to reduce allergen levels. It is likely that clinical phase of allergic airway disease and the degree of airways remodeling represents relevant factors for the clinical outcome of allergen avoidance procedures. Considering the management of respiratory allergy is a complex strategy; it is difficult in real life to distinguish the efficacy of single interventions. However, further studies better quantifying the effects of allergens are needed.

Milk Other Than Breast Milk and the Development of Asthma in Children 3 Years of Age. A Birth Cohort Study (2006⁻2011)

Prevalence of asthma in Australian children is amongst the highest in the world. Although breastfeeding positively influences infant immunity, early introduction of Milk Other than Breast Milk (MOTBM) may also play an important role in the development of Asthma. The aim of this study was to investigate the association between the introduction of MOTBM in the first six months after birth and the development of reported persistent asthma in 3-year olds. A sample of 1121 children was extracted from the Environments for Healthy Living longitudinal birth cohort study. Introduction of MOTBM during the first six months after birth increased almost two-fold the risk of development of persistent asthma after adjusting for other covariates (Adjusted Relative Risk (ARR): 1.71, 95% CI: 1.03⁻2.83, p = 0.038). This study indicates that the introduction of MOTBM in the first six months of life is a risk factor for asthma incidence among 3-year old children. This result is important in explaining the benefits of breastfeeding as part of public health interventions to encourage mothers to increase breastfeeding initiation and duration, and avoid the introduction of MOTBM in the first six months after childbirth.

Methylomic markers of persistent childhood asthma: a longitudinal study of asthma-discordant monozygotic twins

BACKGROUND

Asthma is the most common chronic inflammatory disorder in children. The aetiology of asthma pathology is complex and highly heterogeneous, involving the interplay between genetic and environmental risk factors that is hypothesized to involve epigenetic processes. Our aim was to explore whether methylomic variation in early childhood is associated with discordance for asthma symptoms within monozygotic (MZ) twin pairs recruited from the Environmental Risk (E-Risk) longitudinal twin study. We also aimed to identify differences in DNA methylation that are associated with asthma that develops in childhood and persists into early adulthood as these may represent useful prognostic biomarkers.

RESULTS

We examined genome-wide patterns of DNA methylation in buccal cell samples collected from 37 MZ twin pairs discordant for asthma at age 10. DNA methylation at individual CpG sites demonstrated significant variability within discordant MZ twin pairs with the top-ranked nominally significant differentially methylated position (DMP) located in the HGSNAT gene. We stratified our analysis by assessing DNA methylation differences in a sub-group of MZ twin pairs who remained persistently discordant for asthma at age 18. The top-ranked nominally significant DMP associated with persisting asthma is located in the vicinity of the HLX gene, which has been previously implicated in childhood asthma.

CONCLUSIONS

We identified DNA methylation differences associated with childhood asthma in peripheral DNA samples from discordant MZ twin pairs. Our data suggest that differences in DNA methylation associated with childhood asthma which persists into early adulthood are distinct from those associated with asthma which remits.

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.

Breastfeeding and childhood asthma: systematic review and meta-analysis

Asthma and wheezing disorders are common chronic health problems in childhood. Breastfeeding provides health benefits, but it is not known whether or how breastfeeding decreases the risk of developing asthma. We performed a systematic review and meta-analysis of studies published between 1983 and 2012 on breastfeeding and asthma in children from the general population. We searched the PubMed and Embase databases for cohort, cross-sectional, and case-control studies. We grouped the outcomes into asthma ever, recent asthma, or recent wheezing illness (recent asthma or recent wheeze). Using random-effects meta-analyses, we estimated pooled odds ratios of the association of breastfeeding with the risk for each of these outcomes. We performed meta-regression and stratified meta-analyses. We included 117 of 1,464 titles identified by our search. The pooled odds ratios were 0.78 (95% confidence interval: 0.74, 0.84) for 75 studies analyzing "asthma ever," 0.76 (95% confidence interval: 0.67, 0.86) for 46 studies analyzing "recent asthma," and 0.81 (95% confidence interval: 0.76, 0.87) for 94 studies analyzing recent wheezing illness. After stratification by age, the strong protective association found at ages 0-2 years diminished over time. We found no evidence for differences by study design or study quality or between studies in Western and non-Western countries. A positive association of breastfeeding with reduced asthma/wheezing is supported by the combined evidence of existing studies.

Active or passive exposure to tobacco smoking and allergic rhinitis, allergic dermatitis, and food allergy in adults and children: a systematic review and meta-analysis

BACKGROUND

Allergic rhinitis, allergic dermatitis, and food allergy are extremely common diseases, especially among children, and are frequently associated to each other and to asthma. Smoking is a potential risk factor for these conditions, but so far, results from individual studies have been conflicting. The objective of this study was to examine the evidence for an association between active smoking (AS) or passive exposure to secondhand smoke and allergic conditions.

METHODS AND FINDINGS

We retrieved studies published in any language up to June 30th, 2013 by systematically searching Medline, Embase, the five regional bibliographic databases of the World Health Organization, and ISI-Proceedings databases, by manually examining the references of the original articles and reviews retrieved, and by establishing personal contact with clinical researchers. We included cohort, case-control, and cross-sectional studies reporting odds ratio (OR) or relative risk (RR) estimates and confidence intervals of smoking and allergic conditions, first among the general population and then among children. We retrieved 97 studies on allergic rhinitis, 91 on allergic dermatitis, and eight on food allergy published in 139 different articles. When all studies were analyzed together (showing random effects model results and pooled ORs expressed as RR), allergic rhinitis was not associated with active smoking (pooled RR, 1.02 [95% CI 0.92-1.15]), but was associated with passive smoking (pooled RR 1.10 [95% CI 1.06-1.15]). Allergic dermatitis was associated with both active (pooled RR, 1.21 [95% CI 1.14-1.29]) and passive smoking (pooled RR, 1.07 [95% CI 1.03-1.12]). In children and adolescent, allergic rhinitis was associated with active (pooled RR, 1.40 (95% CI 1.24-1.59) and passive smoking (pooled RR, 1.09 [95% CI 1.04-1.14]). Allergic dermatitis was associated with active (pooled RR, 1.36 [95% CI 1.17-1.46]) and passive smoking (pooled RR, 1.06 [95% CI 1.01-1.11]). Food allergy was associated with SHS (1.43 [1.12-1.83]) when cohort studies only were examined, but not when all studies were combined. The findings are limited by the potential for confounding and bias given that most of the individual studies used a cross-sectional design. Furthermore, the studies showed a high degree of heterogeneity and the exposure and outcome measures were assessed by self-report, which may increase the potential for misclassification.

CONCLUSIONS

We observed very modest associations between smoking and some allergic diseases among adults. Among children and adolescents, both active and passive exposure to SHS were associated with a modest increased risk for allergic diseases, and passive smoking was associated with an increased risk for food allergy. Additional studies with detailed measurement of exposure and better case definition are needed to further explore the role of smoking in allergic diseases.

The impact of smoking in the home on the health outcomes of non-smoker occupants in the UK

Smoking in the home remains a key source of exposure to secondhand smoke for non-smokers, particularly since the UK public smoking ban in 2007. A systematic literature review was conducted to identify all UK evidence on the impact of secondhand smoke exposure in the home on health and behavioural outcomes in non-smoker occupants. MEDLINE, EMBASE and the Cochrane Library were searched to identify all relevant UK empirical studies from 2000 to June 2011. A qualitative overview of the evidence is presented. Exposure to secondhand smoke in UK homes was found to be associated with serious negative health effects in non-smokers, including significantly increased risk of meningococcal carriage (p < 0.001) and disease (p = 0.05) in children and adolescents, cognitive impairment (p < 0.001) in adults, a higher rate of medically attended accidents in children with smoking mothers (p < 0.01), and for non-smoking women, a significant decrease in infant birth weight (p = 0.007). Living in a smoking household significantly increased the risk of future regular smoking in children (p < 0.001). In conclusion, this systematic review has identified strong evidence of an association between secondhand smoke exposure in the home and several serious health conditions. This finding highlights the importance of educating current smokers on the consequences of non-smoker exposure to smoking in the home.

Impact of tobacco smoke on chronic rhinosinusitis: a review of the literature

BACKGROUND

Environmental factors such as inhaled pollutants like cigarette smoke may play a significant role in diseases of the upper airway including chronic rhinosinusitis (CRS). The objectives of this review are to summarize prior studies that describe the correlation between active smoking and secondhand smoke (SHS) on CRS. We also review the pathophysiologic effects of cigarette smoke on sinonasal mucosa and discuss its impact on surgical outcomes of endoscopic sinus surgery (ESS).

METHODS

A literature search was conducted of the PubMed database using the terms "sinusitis" or "rhinosinusitis" and "smoking." Additional search terms of "nasal epithelial" and "smoke" were used to find articles that discussed pathophysiologic effects of tobacco smoke, whereas "secondhand smoke" was added to identify articles analyzing the correlation of SHS and CRS. Finally "endoscopic sinus surgery" and "outcomes" were linked to "smoking" to find articles that analyzed the impact of smoking on surgical results.

RESULTS

We identified 204 articles in the initial search. An additional 72 articles were reviewed for their relevance to the pathophysiologic effects of tobacco smoke while 31 articles were analyzed to determine the correlation of SHS and CRS. Twenty-nine articles were reviewed to analyze the impact of smoking on surgical results.

CONCLUSION

There is clear evidence in the literature that cigarette smoke, either through active smoking or passive exposure to SHS, contributes to CRS. Recent prospective studies suggest that active smoking is not a contraindication to ESS, whereas the impact of smoking volume and long-term smoking after ESS has not been sufficiently evaluated.

Prenatal and passive smoke exposure and incidence of asthma and wheeze: systematic review and meta-analysis

OBJECTIVES

Exposure to passive smoke is a common and avoidable risk factor for wheeze and asthma in children. Substantial growth in the prospective cohort study evidence base provides an opportunity to generate new and more detailed estimates of the magnitude of the effect. A systematic review and meta-analysis was conducted to provide estimates of the prospective effect of smoking by parents or household members on the risk of wheeze and asthma at different stages of childhood.

METHODS

We systematically searched Medline, Embase, and conference abstracts to identify cohort studies of the incidence of asthma or wheeze in relation to exposure to prenatal or postnatal maternal, paternal, or household smoking in subjects aged up to 18 years old. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were estimated by using random effects model.

RESULTS

We identified 79 prospective studies. Exposure to pre- or postnatal passive smoke exposure was associated with a 30% to 70% increased risk of incident wheezing (strongest effect from postnatal maternal smoking on wheeze in children aged ≤2 years, OR = 1.70, 95% CI = 1.24-2.35, 4 studies) and a 21% to 85% increase in incident asthma (strongest effect from prenatal maternal smoking on asthma in children aged ≤2 years, OR = 1.85, 95% CI = 1.35-2.53, 5 studies).

CONCLUSIONS

Building upon previous findings, exposure to passive smoking increases the incidence of wheeze and asthma in children and young people by at least 20%. Preventing parental smoking is crucially important to the prevention of asthma.

Longitudinal study of parental smoking habits and development of asthma in early childhood

OBJECTIVE

This study examined the association between parental smoking habits and the development of asthma in early childhood by using representative samples.

METHODS

The survey subjects included all of the 53,575 babies born in Japan during the periods January 10-17 and July 10-17, 2001. The families of the subjects were asked to complete questionnaires that were delivered by post at 6 months, 1 year 6 months, 2 years 6 months, 3 years 6 months, and 4 years 6 months postpartum. The first survey contained questions regarding the smoking habits of the parents. The second to fifth surveys asked if the child had needed medical attention for the treatment of asthma.

RESULTS

Data from 36,888 subjects (collection rate: 68.9%) were analyzed. The 4-year cumulative incidence of asthma was 12.0%. Maternal indoor smoking significantly increased the risk of asthma development in children, 4-year risk 14.4% vs. 11.7%, risk ratio=1.24, 95% CI: 1.11 to 1.38. No statistically significant association was found between paternal smoking and asthma development in children.

CONCLUSIONS

In order to prevent the development of asthma in early childhood, it is necessary to formulate measures to stop or discourage maternal smoking.

The genetics of asthma and allergic disease: a 21st century perspective

Asthma and allergy are common conditions with complex etiologies involving both genetic and environmental contributions. Recent genome-wide association studies (GWAS) and meta-analyses of GWAS have begun to shed light on both common and distinct pathways that contribute to asthma and allergic diseases. Associations with variation in genes encoding the epithelial cell-derived cytokines, interleukin-33 (IL-33) and thymic stromal lymphopoietin (TSLP), and the IL1RL1 gene encoding the IL-33 receptor, ST2, highlight the central roles for innate immune response pathways that promote the activation and differentiation of T-helper 2 cells in the pathogenesis of both asthma and allergic diseases. In contrast, variation at the 17q21 asthma locus, encoding the ORMDL3 and GSDML genes, is specifically associated with risk for childhood onset asthma. These and other genetic findings are providing a list of well-validated asthma and allergy susceptibility genes that are expanding our understanding of the common and unique biological pathways that are dysregulated in these related conditions. Ongoing studies will continue to broaden our understanding of asthma and allergy and unravel the mechanisms for the development of these complex traits.

Epidemiology of asthma: risk factors for development

This comprehensive review of the recent literature was undertaken to determine the current state of knowledge of the risk factors involved in the development of asthma in order to focus investigations in a proposed new longitudinal birth cohort study. The origins of asthma appear to lie in the prenatal and early postnatal period, and renewed investigations in this period with long-term close follow-up and objective phenotypic characterization will help to unravel the role of the multiple putative environmental factors in the development of asthma. It is only after understanding these effects that one can hope to design rational prevention studies for asthma.

Phenotypes of childhood asthma: are they real?

It has been suggested that there are several distinct phenotypes of childhood asthma or childhood wheezing. Here, we review the research relating to these phenotypes, with a focus on the methods used to define and validate them. Childhood wheezing disorders manifest themselves in a range of observable (phenotypic) features such as lung function, bronchial responsiveness, atopy and a highly variable time course (prognosis). The underlying causes are not sufficiently understood to define disease entities based on aetiology. Nevertheless, there is a need for a classification that would (i) facilitate research into aetiology and pathophysiology, (ii) allow targeted treatment and preventive measures and (iii) improve the prediction of long-term outcome. Classical attempts to define phenotypes have been one-dimensional, relying on few or single features such as triggers (exclusive viral wheeze vs. multiple trigger wheeze) or time course (early transient wheeze, persistent and late onset wheeze). These definitions are simple but essentially subjective. Recently, a multi-dimensional approach has been adopted. This approach is based on a wide range of features and relies on multivariate methods such as cluster or latent class analysis. Phenotypes identified in this manner are more complex but arguably more objective. Although phenotypes have an undisputed standing in current research on childhood asthma and wheezing, there is confusion about the meaning of the term 'phenotype' causing much circular debate. If phenotypes are meant to represent 'real' underlying disease entities rather than superficial features, there is a need for validation and harmonization of definitions. The multi-dimensional approach allows validation by replication across different populations and may contribute to a more reliable classification of childhood wheezing disorders and to improved precision of research relying on phenotype recognition, particularly in genetics. Ultimately, the underlying pathophysiology and aetiology will need to be understood to properly characterize the diseases causing recurrent wheeze in children.

Maternal smoking and environmental tobacco smoke exposure and the risk of allergic diseases in Japanese infants: the Osaka Maternal and Child Health Study

PURPOSE

It remains controversial whether environmental tobacco smoke increases the risk of allergic diseases. The present prospective cohort study examined whether in utero exposure to maternal smoking and postnatal exposure to environmental tobacco smoke were associated with the development of wheeze, asthma, and atopic eczema in Japanese infants.

METHODS

Study subjects included 763 infants. Data were obtained through the use of questionnaires completed by the mother during pregnancy and at 2 to 9 and 16 to 24 months postdelivery. Information regarding maternal smoking during pregnancy and postnatal exposure to environmental tobacco smoke was collected at 2 to 9 months postdelivery, and information on allergic symptoms was collected when the infant was between 16 to 24 months of age. Cases were defined according to criteria of the International Study of Asthma and Allergies in Childhood for wheeze and atopic eczema. Additionally, doctor-diagnosed asthma and atopic eczema were identified. Adjustment was made for maternal age, family income, maternal and paternal education, parental history of asthma, atopic eczema, allergic rhinitis, indoor domestic pets, baby's older siblings, baby's sex, birth weight, and time of surveys.

RESULTS

The cumulative incidence of wheeze, atopic eczema, doctor-diagnosed asthma, and doctor-diagnosed atopic eczema was 22.1%, 18.6%, 4.3%, and 9.0%, respectively. Maternal smoking during pregnancy was not related to the risk of wheeze, whereas postnatal maternal smoking in the same room as the child increased the risk of wheeze. No significant association was observed between perinatal tobacco smoke exposure and the development of asthma and atopic eczema.

CONCLUSIONS

Our findings suggest that postnatal maternal smoking might be associated with an increased risk of wheeze in Japanese infants.

Are girls more susceptible to the effects of prenatal exposure to tobacco smoke on asthma?

BACKGROUND

Prenatal exposure to tobacco smoke through mother's smoking increases the risk of developing asthma later in life. A recent study suggested that this effect is present only in girls. We explored potential differences in susceptibility between boys and girls.

METHODS

We followed all 58,841 Finnish singleton babies born in 1987 through 5 nationwide registries for 7 years and identified all cases of doctor-diagnosed asthma (ICD-9 code 493). The birth registry provided categorical information on the mother's smoking during pregnancy: no smoking (reference), low exposure (<10 cigarettes per day), and high exposure (>10 cigarettes per day).

RESULTS

In girls the cumulative incidence of asthma was 0.0245 in the reference group, 0.0310 in the low maternal smoking group (risk difference = 0.0065; 95% CI = 0.0053-0.0076), and 0.0360 in the high maternal smoking group (0.0115; 0.0096-0.0133). The corresponding cumulative incidences for boys were 0.0405, 0.0501 (0.0096; 0.0089-0.0103), and 0.0522 (0.0117; 0.0091-0.0142). In logistic regression analysis adjusting for confounding, the combined effect of male sex and high maternal smoking (compared with female sex and no smoking) was 112% excess risk. This corresponded closely to what would be expected from the additive independent effects of male sex (67% excess risk) and high maternal smoking (44% excess risk).

CONCLUSIONS

Effects of maternal smoking during pregnancy on the risk of developing asthma are similar in boys and girls, with no interaction on an additive scale.

Environmental factors and allergic disorders

Despite numerous studies on possible associations between environmental exposure and allergic disorders, any conclusions made remain a matter of controversy. We conducted a review of evidence in relation to environmental and nutritional determinants and wheeze, asthma, atopic dermatitis, and allergic rhinitis. Identified were 263 articles for analysis after consideration of 1093 papers that were published since 2000 and selected by electronic search of the PubMed database using keywords relevant to epidemiological studies. Most were cross-sectional and case-control studies. Several prospective cohort studies revealed inconsistent associations between various environmental factors and the risk of any allergic disorder. Therefore, the evidence was inadequate to infer the presence or absence of a causal relationship between various environmental exposures and allergic diseases. However, evidence is suggestive of positive associations of allergies with heredity. Because almost all the studies were performed in Western countries, the application of these findings to people in other countries, including Japan, may not be appropriate. Further epidemiological information gained from population-based prospective cohort studies, in particular among Japanese together with other Asians, is needed to assess causal relationships between various environmental factors and allergic diseases.

[IgE and respiratory disease]

INTRODUCTION

IgE is known to provide the biological basis for allergy and immediate hypersensitivity. However, recent data provide some evidence that IgE responses are involved in other inflammatory processes apart from allergy, including several respiratory diseases.

STATE OF THE ART

IgE binds to mast cells and basophils but also to other inflammatory cells, which are involved in non-allergic processes. IgE has a role in antigen presentation and is implicated in a number of other immune mechanisms. In the airways, IgE plays an important role in bronchial hyperactivity, even in the absence of an allergen. Epidemiological studies have demonstrated that IgE response is related not only to allergy but also to asthma symptoms, in the presence or absence of atopy, as well as exposure to cigarette smoke. IgE response is altered in several respiratory diseases including extrinsic and intrinsic asthma and allergic bronchopulmonary aspergillosis.

CONCLUSION AND PERSPECTIVES

Since anti-IgE monoclonal antibodies are now available for administration to humans, a better understanding of the IgE response may allow the identification of novel therapeutic targets in the field of respiratory disease.

Wheezing, asthma, hayfever, and atopic eczema in childhood following exposure to tobacco smoke in fetal life

BACKGROUND

Prenatal maternal smoking has been associated with adverse respiratory effects in childhood such as lung deficits and wheezing, but results concerning asthma, hayfever, and atopic eczema are inconsistent.

OBJECTIVE

In the present study, we investigate the effects of maternal smoking in pregnancy on asthma, hayfever, atopic eczema, and wheezing in the offspring up to the age of 14-18.

METHODS

The study was based on a cohort of mothers enrolled during midwife visits around the 36th week of gestation in Odense and Aalborg, Denmark, 1984-1987. Singleton, live born children (n = 11,144) were followed-up in 2002 to obtain a childhood history of atopic diseases, by means of questionnaires to the parents. Multivariate logistic regression analyses for medical diagnoses of asthma, hayfever, atopic eczema, and symptoms of wheezing before the age of 3, were carried out on 7844 children.

RESULTS

After adjustment for confounders, late prenatal smoke exposure was associated with wheezing, with an odds ratio (OR) of 1.2, and a 95% confidence interval (CI) of 1.1-1.5. Furthermore, slightly reduced estimates for hayfever (OR 0.8, CI 0.7-1.0) and atopic eczema (OR 0.8, CI 0.7-0.9) were obtained for children exposed in late pregnancy compared with non-exposed.

CONCLUSION

Late gestational smoke exposure was associated with wheezing but not with asthma, while null or even protective estimates were indicated for hayfever and atopic eczema. However, lack of control options for hereditary factors may have affected the results.

The effect of environmental tobacco smoke exposure on allergic sensitization and allergic rhinitis in adults

BACKGROUND

There is only little and furthermore conflicting knowledge about the relationship between passive smoking and allergy in adults. In this work, we assess the association between exposure to environmental tobacco smoke (ETS) at home or at work, and allergic sensitization and allergic rhinitis in 4093 German adults.

METHODS

Our study population comes from the German National Health Survey 1998 of which we analyzed 4093 adults (17-79 years) being non-smokers and having complete information on passive smoking and allergy. The association between ETS exposure and allergic sensitization and allergic rhinitis was assessed using logistic regression models.

RESULTS

The effect of ETS exposure on allergic sensitization was biggest at the workplace [adjusted OR = 1.17 (0.97, 1.41)]; the same could be observed with respect to allergic rhinitis [adjusted OR = 1.20 (0.96, 1.51)]. There was no effect of ETS exposure at home on both allergic sensitization [adjusted OR = 0.99 (0.76, 1.29)] and allergic rhinitis [adjusted OR = 1.05 (0.76, 1.43)] in our analysis.

CONCLUSIONS

The findings from our study show a statistically non-significant tendency that exposure to ETS at the workplace increases allergic sensitization and allergic rhinitis in adults. This tendency could not be observed with respect to ETS exposure at home.

PRACTICAL IMPLICATIONS

Exposure to ETS at the workplace should be minimized in order to reduce the risk of allergic sensitization, and allergic rhinitis.

Food allergy: what can be done to prevent progression to asthma?

OBJECTIVES

The primary objective of this review is to discuss risk factors for asthma development in food allergen-sensitized children. In the paper we discuss the possible measures to prevent progression to asthma by allergen and other adjuvant factor avoidance.

DATA SOURCES

A review from literature of articles on these topics was performed.

STUDY SELECTION

Relevant publications on asthma risk factors and implementation of protective factors were critically evaluated.

RESULTS

Children with familiar history of atopy and sensitization to food proteins in early infancy are at high risk of subsequent respiratory allergic diseases and require specific prevention. Because early allergic sensitization is a significant risk factor for later development of asthma, prevention of asthma by early allergen avoidance is mandatory in high-risk children. Adjuvant factors such as tobacco smoke and mold exposure may act as nonspecific triggers for the development of atopy. The role of protective factors such as infections in early life, breast-feeding, a "healthy" diet needs to be evaluated in prospective studies. Pharmacologic intervention with antihistamines led to significant reduction in incidence of asthma in high-risk children, but confirmatory longitudinal studies in large populations are necessary.

CONCLUSIONS

There is now accumulating evidence that preventing exposure to house-dust mite may significantly reduce the prevalence of childhood asthma. However, allergen avoidance can not be recommended as the only strategy. Avoidance of adjuvant factors and implementation of potential protective factors aimed to reduce the risk to progression to asthma need to be evaluated in prospective studies.

The influence of simultaneous whole body exposure to cigarette smoke and low-protein diet feeding on fertility, reproduction, and progeny of rats

The aim of the present study was to evaluate the toxicological influence of different concentrations of tobacco smoke and low-protein diet on fertility, reproduction, and survival of offspring of Wistar female rats. We studied three generations, two litters in each. There were 192 animals in parent generation. Animals were exposed to three different concentrations of tobacco smoke that were reflected by the carbon monoxide (CO) concentration (500, 1000, and 1500 mg CO/m3 air) during 11 weeks (six before and two weeks during mating, and three weeks of pregnancy). Additionally, animals were divided into two subgroups that were fed normal or low-protein diet. In the present study, we concentrated on the indices describing the reproduction ability, fertility, and rearing of pups of mothers exposed to tobacco smoke. The parameters of newborns survival were estimated also. We concluded that neither tobacco smoke exposure nor the low-protein diet changed the duration of pregnancy. The tobacco smoke in all doses and low-protein diet had a negative influence on fertility, reproduction, and survival of newborns from exposed mothers. This influence was mainly attributed to the tobacco smoke exposure. The levels of carboxyhaemoglobin were increasing with increasing tobacco smoke concentration.