Long-term effects of breastfeeding, maternal smoking during pregnancy, and recurrent lower respiratory tract infections on asthma in children

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).

The burden of recurrent respiratory tract infections in adult population: a population-based study in primary care

BACKGROUND

Viral infections are the main original cause of recurrent respiratory tract infections (RRTIs), but their complications and recurrences are due to bacteria as well. While some operational definitions and epidemiology of RRTIs are reported in paediatrics, no similar definitions have been proposed for adults.

AIM

To assess the epidemiology and characteristics of RRTIs in the adult population.

DESIGN AND SETTING

Cohort study in the primary care setting.

METHODS

Using the Health Search Database, we selected a cohort of patients aged 18 years or older between 2002 and 2022. Yearly, we counted upper and lower respiratory tract infections (RTIs) per patient. We investigated 2 cut-offs defining RRTIs, nominally 3+ RRTIs/patient/year or greater than the mean value of RTIs/patient/year. The associations between these two event definitions and the correlates defining the patients' vulnerability were assessed by estimating a logistic regression model.

RESULTS

Over the study years, the mean number of RTIs/patient/year ranged from 0.07-0.16 or 1.10-1.13 events, when the denominator was formed by the overall population or those diagnosed with RTIs, respectively. When the analysis was focussed on 2022, we obtained 0.2% (1.3% among those with RTIs) or 13% (11.3% among those with RTIs) cases of RRTIs, using a cut-off of 3+ or >=0.16 events (mean value/patient), respectively. Consistent associations were found for these two operational definitions and the investigated clinical correlates.

CONCLUSION

We provided evidence on the epidemiology and concurrent/predisposing factors of RRTIs in adults. These data should support health authorities and general practitioners for the application of the most appropriate preventive and/or treatment strategies.

Persistent ciprofloxacin exposure induced the transformation of Klebsiella pneumoniae small colony variant into mucous phenotype

Introduction

Small colony variant (SCV) is a bacterial phenotype closely related to persistent and recurrent infections. SCVs are mutations that occur within bacterial populations, resulting in a change in bacterial morphology and the formation of small colonies. This morphological change may enhance bacterial resistance to antibiotics and contribute to persistent and recurrent infections.

Methods

We isolated Klebsiella pneumoniae (KPN) and its SCV from a child with recurrent respiratory tract infections. KPN and SCV were treated with subinhibitory concentrations of antibiotics. growth curves, serum resistance experiments, macrophage phagocytosis experiments and whole genome sequencing were used to characterize KPN and SCV.

Results

After treating KPN and SCV with subinhibitory concentrations of antibiotics, we found that ciprofloxacin induced the SCV transition to the mucoid phenotype. We found that the growth of mucoid Klebsiella pneumoniae was significantly slower than maternal strain and SCV though growth curves. Serum resistance experiments showed that mucoid strains had significantly higher serum resistance compared to maternal strain and SCV. Macrophage phagocytosis experiments revealed that SCV had significantly higher intracellular survival rates compared to maternal strain and mucoid strains. Differential gene analysis of three strains revealed that the mucoid strain contained DNA polymerase V subunit UmuC gene on the plasmid, while the SCV strain had an additional IcmK family IV secretion protein on its plasmid.

Discussion

Our study showed the SCV of KPN changed to a mucoid colony when exposed to subinhibitory concentrations of ciprofloxacin. The higher resistance of serum of mucoid colonies was possibly related to the UmuC gene, while the increased intracellular survival of SCV may be related to the IcmK family type IV secretion proteins.

CT imaging features of paranasal sinuses in children with primary ciliary dyskinesia

BACKGROUND

Primary ciliary dyskinesia (PCD) causes impaired mucociliary clearance and results in chronic pulmonary and sinonasal symptoms.

OBJECTIVES

To study the CT imaging features of paranasal sinuses in children with PCD.

MATERIALS AND METHODS

17 PCD patients ranged from 4 to 13 years, a mean age of 7.9 ± 3.3 years, were included in the final analysis. Patients with non-PCD chronic rhinosinusitis (CRS) who accepted maxillary balloon catheter dilation were included in the control group. Paranasal sinuses CT scans were scored according to the Lund-Mackay staging system. The correlation between age and Lund-Mackay score was analyzed.

RESULTS

100% (17/17) had rhinosinusitis, 52.9% (9/17) had lung consolidation, 64.7% (11/17) had atelectasis, 35.3% (6/17) had bronchiectasis, and 47.1% (8/17) had a history of neonatal respiratory distress. The mean Lund-Mackay score of PCD patients was 14.2 ± 3.1, that of non-PCD CRS patients was 14.6 ± 5.5, the difference was not significant (p = .79). There was a significant inverse correlation between age and Lund-Mackay score in PCD patients (r = -0.530, p = .029) but not in non-PCD CRS patients (r = -0.168, p = .519).

CONCLUSION

Radiographic severity of rhinosinusitis in PCD patients was similar to the control population but decreased with age.

SIGNIFICANCE

First time to propose radiographic severity of rhinosinusitis in pediatric patients with PCD might decrease with age.

The Association of Breastfeeding With Childhood Asthma: A Case-Control Study From India

Background

The role of breastfeeding in childhood asthma has long been controversial. The majority of research pertains to developed countries with scant literature available in a developing country like India, where a different asthma phenotype is prevalent. This study examined the association of breastfeeding duration and exclusiveness with childhood asthma and its severity, as measured by peak expiratory flow rate (PEFR) in India.

Methodology

We conducted a matched case-control study in Pune, India. A total of 180 children with asthma (cases) and 180 without the disease (controls) were included. A standardized questionnaire recorded demographics and medical and breastfeeding history. PEFR readings were obtained from each child. Conditional logistic regression and linear regression were used to explore the association of breastfeeding with asthma and PEFR, respectively.

Results

The median duration of breastfeeding among cases was [5 (2.5-10)] months as compared to controls [9 (3.5-16.8)] months. The prevalence of exclusive breastfeeding among mothers was 60% (50% among cases and 69% among controls). Exclusive breastfeeding was associated with a 46% lower likelihood of having asthma with a probability (p-value) of 0.025 where the odds ratio (OR) was 1.85, with a 95% confidence interval (CI) of 1.08 to 3.16. Breastfeeding duration was significantly associated with a lower likelihood of having asthma (p = 0.001) (OR 0.87; 95% CI 0.79-0.94). One-month increase in the duration of breastfeeding was associated with a 23% reduced risk of the disease. The odds of maternal asthma [21.4 (4.22-109.36)], paternal smoking [1.44 (0.22-0.86)], and maternal smoking [5.14 (1.78-14.80)] were higher among children with asthma as compared to children without asthma. The weight of the child and duration of breastfeeding were negatively associated with PEFR. Maternal asthmatic history, associated allergies, paternal smoking, and parents’ education were positively associated with PEFR for the overall sample.

Conclusion

Prolonged and exclusive breastfeeding was found to be a protective factor against the development of asthma. Promotion of breastfeeding and smoking cessation should be a priority in the control of childhood asthma. Further research should be conducted to explore the negative correlation between duration and frequency of breastfeeding and PEFR.

Breastfeeding and risk of childhood asthma: a systematic review and meta-analysis

OBJECTIVE

To investigate the relationship between breastfeeding and the development of paediatric asthma.

METHODS

A systematic review and meta-analysis was conducted with MEDLINE, Embase, CINAHL and ProQuest Nursing and Allied Health source databases. Retrospective/prospective cohorts in children aged <18 years with breastfeeding exposure reported were included. The primary outcome was a diagnosis of asthma by a physician or using a guideline-based criterion. A secondary outcome was asthma severity.

RESULTS

42 studies met inclusion criteria. 37 studies reported the primary outcome of physician-/guideline-diagnosed asthma, and five studies reported effects on asthma severity. Children with longer duration/more breastfeeding compared to shorter duration/less breastfeeding have a lower risk of asthma (OR 0.84, 95% CI 0.75-0.93; I2 = 62.4%). Similarly, a lower risk of asthma was found in children who had more exclusive breastfeeding versus less exclusive breastfeeding (OR 0.81, 95% CI 0.72-0.91; I2=44%). Further stratified analysis of different age groups demonstrated a lower risk of asthma in the 0-2-years age group (OR 0.73, 95% CI 0.63-0.83) and the 3-6-years age group (OR 0.69, 95% CI 0.55-0.87); there was no statistically significant effect on the ≥7-years age group.

CONCLUSION

The findings suggest that the duration and exclusivity of breastfeeding are associated with a lower risk of asthma in children aged <7 years.

[Smoking and Breastfeeding - CNGOF-SFT Expert Report and Guidelines on the management for Smoking Management During Pregnancy]

INTRODUCTION

The consequences of smoking have been studied more during pregnancy than during breastfeeding. There is a passage of nicotine and other substances in breast milk and some modifications of milk composition. The objectives of this chapter are to study the benefits of breastfeeding in women who smoke, and the adaptation of smoking, medication and behavioral habits in case of incomplete withdrawal to better guide women.

METHODS

The Medline database, the Cochrane Library and foreign guidelines from 1999 to 2019 have been consulted.

RESULTS

The conservation of the benefit of breastfeeding in smokers with regard to the prevention of respiratory infections, infantile colic, cognitive deficits, obesity, sudden infant death, is not known to date. It is therefore not recommended to include smoking status in the choice of feeding mode for the newborn (professional agreement). However, since breastfeeding is a factor associated with a reduction in smoking and/or withdrawal (NP2), it is recommended to promote breastfeeding in non-weaned women in order to limit smoking (grade B). The use of nicotine replacement therapy is possible during breastfeeding (professional agreement). In the absence of data, bupropion (Zyban®) and varenicline (Champix®) are not recommended for women who are breastfeeding (professional agreement). A free interval between smoking and breastfeeding reduces the concentration of nicotine in milk (NP4). For non-weaned women who are breastfeeding, it is therefore recommended not to smoke just before breastfeeding (professional agreement).

CONCLUSION

The results indicate that breastfeeding is possible in smokers, although less often initiated by them. If the conservation of its benefits for the child is not demonstrated to date, breastfeeding allows the mother to limit smoking.

Protective Effect of Breastfeeding on the Adverse Health Effects Induced by Air Pollution: Current Evidence and Possible Mechanisms

Air pollution is a major social, economic, and health problem around the world. Children are particularly susceptible to the negative effects of air pollution due to their immaturity and excessive growth and development. The aims of this narrative review were to: (1) summarize evidence about the protective effects of breastfeeding on the adverse health effects of air pollution exposure, (2) define and describe the potential mechanisms underlying the protective effects of breastfeeding, and (3) examine the potential effects of air pollution on breastmilk composition and lactation. A literature search was conducted using electronic databases. Existing evidence suggests that breastfeeding has a protective effect on adverse outcomes of indoor and outdoor air pollution exposure in respiratory (infections, lung function, asthma symptoms) and immune (allergic, nervous and cardiovascular) systems, as well as under-five mortality in both developing and developed countries. However, some studies reported no protective effect of breastfeeding or even negative effects of breastfeeding for under-five mortality. Several possible mechanisms of the breastfeeding protective effect were proposed, including the beneficial influence of breastfeeding on immune, respiratory, and nervous systems, which are related to the immunomodulatory, anti-inflammatory, anti-oxidant, and neuroprotective properties of breastmilk. Breastmilk components responsible for its protective effect against air pollutants exposure may be long chain polyunsaturated fatty acids (LC PUFA), antioxidant vitamins, carotenoids, flavonoids, immunoglobins, and cytokines, some of which have concentrations that are diet-dependent. However, maternal exposure to air pollution is related to increased breastmilk concentrations of pollutants (e.g., Polycyclic aromatic hydrocarbons (PAHs) or heavy metals in particulate matter (PM)). Nonetheless, environmental studies have confirmed that breastmilk's protective effects outweigh its potential health risk to the infant. Mothers should be encouraged and supported to breastfeed their infants due to its unique health benefits, as well as its limited ecological footprint, which is associated with decreased waste production and the emission of pollutants.

Association of Breastfeeding and Air Pollution Exposure With Lung Function in Chinese Children

IMPORTANCE

Breastfeeding and exposure to ambient air pollutants have been found to be independently associated with respiratory health in children; however, previous studies have not examined the association of breastfeeding as a potential moderator of the association.

OBJECTIVE

To assess associations of breastfeeding and air pollution with lung function in children.

DESIGN, SETTING, AND PARTICIPANTS

Using a cross-sectional study design, children were recruited from 62 elementary and middle schools located in 7 Chinese cities from April 1, 2012, to October 31, 2013. Data analyses were conducted from November 1, 2018, to March 31, 2019.

EXPOSURES

Long-term concentrations of airborne particulate matter with a diameter of 1 μm or less (PM1), airborne particulate matter with a diameter of 2.5 μm or less (PM2.5), airborne particulate matter with a diameter of 10 μm or less (PM10), and nitrogen dioxide were estimated using a spatial statistical model matched to children's geocoded home addresses, and concentrations of PM10, sulfur dioxide, nitrogen dioxide, and ozone were measured by local air monitoring stations.

MAIN OUTCOMES AND MEASURES

Breastfeeding was defined as maternal report of having mainly breastfed for longer than 3 months. Lung function was measured using portable electronic spirometers. Using previously published predicted spirometric values for children in Northeast China as the reference, lung impairment was defined as forced vital capacity (FVC) less than 85%, forced expiratory volume in the first second of expiration less than 85%, peak expiratory flow less than 75%, or maximum midexpiratory flow less than 75%.

RESULTS

Participants included 6740 children (mean [SD] age, 11.6 [2.1] years; 3382 boys [50.2%]). There were 4751 children (70.5%) who were breastfed. Mean (SD) particulate matter concentrations ranged from 46.8 (6.5) μg/m3 for PM1 to 95.6 (9.8) μg/m3 for PM10. The prevalence of lung function impairment ranged from 6.8% for peak expiratory flow to 11.3% for FVC. After controlling for age, sex, and other covariates, 1-interquartile range greater concentration of pollutants was associated with higher adjusted odds ratios (AORs) for lung function impairment by FVC among children who were not breastfed compared with those who were (PM1: AOR, 2.71 [95% CI, 2.02-3.63] vs 1.20 [95% CI, 0.97-1.48]; PM2.5: AOR, 2.27 [95% CI, 1.79-2.88] vs 1.26 [95% CI, 1.04-1.51]; and PM10: AOR, 1.93 [95% CI, 1.58-2.37] vs 1.46 [95% CI, 1.23-1.73]). Younger age (<12 years) was associated with lower lung function impairment among the children who had been breastfed. In children from elementary schools, 1-interquartile range greater concentration of pollutants was associated with higher AORs for lung function impairment by FVC among children who had not been breastfed compared with those who had (PM1: AOR, 6.43 [95% CI, 3.97-10.44] vs 1.89 [95% CI, 1.28-2.80]; PM2.5: AOR, 3.83 [95% CI, 2.63-5.58] vs 1.50 [95% CI, 1.12-2.01]; and PM10: AOR, 2.61 [95% CI, 1.90-3.57] vs 1.52 [95% CI, 1.19-1.95]). Results from linear regression models also showed associations of air pollution with worse lung function among children who were not breastfed compared with their counterparts who were breastfed, especially for FVC (PM1: β, -240.46 [95% CI, -288.71 to -192.21] vs -38.21 [95% CI, -69.27 to -7.16] mL) and forced expiratory volume in the first second of expiration (PM1: β, -201.37 [95% CI, -242.08 to -160.65] vs -30.30 [95% CI, -57.66 to -2.94] mL).

CONCLUSIONS AND RELEVANCE

In this study, breastfeeding was associated with lower risk of lung function impairment among children in China exposed to air pollution, particularly among younger children.

Infant milk-feeding practices and food allergies, allergic rhinitis, atopic dermatitis, and asthma throughout the life span: a systematic review

BACKGROUND

During the Pregnancy and Birth to 24 Months Project, the USDA and Department of Health and Human Services initiated a review of evidence on diet and health in these populations.

OBJECTIVES

The aim of these systematic reviews was to examine the relation of 1) never versus ever feeding human milk, 2) shorter versus longer durations of any human milk feeding, 3) shorter versus longer durations of exclusive human milk feeding prior to infant formula introduction, 4) feeding a lower versus higher intensity of human milk to mixed-fed infants, and 5) feeding a higher intensity of human milk by bottle versus breast with food allergies, allergic rhinitis, atopic dermatitis, and asthma.

METHODS

The Nutrition Evidence Systematic Review team conducted systematic reviews with external experts. We searched CINAHL, Cochrane, Embase, and PubMed for articles published between January 1980 and March 2016, dual-screened the results according to predetermined criteria, extracted data from and assessed the risk of bias for each included study, qualitatively synthesized the evidence, developed conclusion statements, and graded the strength of the evidence.

RESULTS

The systematic reviews numbered 1-5 above included 44, 35, 1, 0, and 0 articles, respectively. Moderate, mostly observational, evidence suggests that 1) never versus ever being fed human milk is associated with higher risk of childhood asthma, and 2) among children and adolescents who were fed human milk as infants, shorter versus longer durations of any human milk feeding are associated with higher risk of asthma. Limited evidence does not suggest associations between 1) never versus ever being fed human milk and atopic dermatitis in childhood or 2) the duration of any human milk feeding and allergic rhinitis and atopic dermatitis in childhood.

CONCLUSIONS

Moderate evidence suggests that feeding human milk for short durations or not at all is associated with higher childhood asthma risk. Evidence on food allergies, allergic rhinitis, and atopic dermatitis is limited.

Effect of Secondary Cigarette Smoke from Household Members on Breastfeeding Duration: A Prospective Cohort Study

OBJECTIVE

Maternal smoking and exposure to tobacco smoke is one modifiable risk factor that affects breastfeeding initiation and duration. We prospectively examine the effects of maternal and paternal smoking and other family members' smoking status on the duration of breastfeeding.

MATERIALS AND METHODS

A cohort of 1,277 mother-infant pairs admitted to the postpartum units of four major public hospitals in Hong Kong. Demographic data, maternal, paternal and household smoking habits, and other potential confounding variables were collected via self-reported questionnaires during the postnatal hospitalization. Breastfeeding status after hospital discharge was assessed through telephone follow-up up to 12 months postpartum, or until participants were no longer breastfeeding. If the participant had weaned during that follow-up interval, she was asked to report the total duration (in weeks) of both any and exclusive breastfeeding.

RESULTS

A total of 1,240 (97%) mother-infant pairs completed followed up, 2.5% were smokers, 29.2% of their partners smoked, and 11.3% had another smoker living in their home. Maternal and other family members' smoking predicted breastfeeding cessation. When compared with mothers in nonsmoking family, those exposed to two or more family members who smoked had approximately a 30% increased risk of breastfeeding cessation (adjusted hazard ratio [aHR] = 1.31; 95% CI 1.01-1.68).

CONCLUSION

Mothers who were exposed to two or more smokers in the household had a significantly shorter duration of any breastfeeding at 12-month follow-up.

Maternal smoking in pregnancy and its influence on childhood asthma

Maternal smoking in pregnancy (MSP) is a large modifiable risk factor for pregnancy related mortality and morbidity and also the most important known modifiable risk factor for asthma. This review summarises the effects of MSP throughout infancy, childhood and adolescence with regards to asthma (development and severity). Firstly, the direct damage caused by nicotine on fetal lung development, fetal growth and neuronal differentiation is discussed, as well as the indirect effects of nicotine on placental functioning. Secondly, the effects of MSP on later immune functioning resulting in increased infection rate are summarised and details are given on the effects of MSP modulating airway hyperreactivity, reducing lung function and therefore increasing asthma morbidity. Furthermore, epigenetic effects are increasingly being recognised. These can also result in transgenerational detrimental effects induced by cigarette smoke. In summary, the causal relationship between MSP and asthma development is well documented and presents a major health problem for generations to come. The high prevalence of MSP is alarming and epigenetic effects of nicotine on immune functioning potentiate this danger. A considerable part of the increase in asthma prevalence worldwide is due to MSP.

Evaluating the efficacy of breastfeeding guidelines on long-term outcomes for allergic disease

BACKGROUND

WHO guidelines advocate breastfeeding for 6 months, and EAACI guideline recommends exclusive breastfeeding for 4-6 months. However, evidence for breastfeeding to prevent asthma and allergic disease is conflicting. We examined whether following recommended breastfeeding guidelines alters the long-term risks of asthma, eczema, rhinitis or atopy.

METHODS

The effect of nonexclusive (0, >0-6, >6 months) and exclusive breastfeeding (0, >0-4, >4 months) on repeated measures of asthma (10, 18 years), eczema, rhinitis, and atopy (1-or-2, 4, 10, 18 years) risks was estimated in the IoW cohort (n = 1456) using log-linear models with generalized estimating equations. The Food Allergy and Intolerance Research (FAIR) cohort (n = 988), also from the IoW, was examined to replicate results.

RESULTS

Breastfeeding (any or exclusive) had no effect on asthma and allergic disease in the IoW cohort. In the FAIR cohort, any breastfeeding for >0-6 months protected against asthma at 10 years (RR = 0.50, 95% CI = 0.32-0.79, P = 0.003), but not other outcomes, whilst exclusive breastfeeding for >4 months protected against repeated rhinitis (RR = 0.36, 95% CI = 0.18-0.71, P = 0.003). Longer breastfeeding was protective against late-onset wheeze in the IoW cohort.

CONCLUSION

The protective effects of nonexclusive and exclusive breastfeeding against long-term allergic outcomes were inconsistent between these colocated cohorts, agreeing with previous observations of heterogeneous effects. Although breastfeeding should be recommended for other health benefits, following breastfeeding guidelines did not appear to afford a consistent protection against long-term asthma, eczema, rhinitis or atopy. Further research is needed into the long-term effects of breastfeeding on allergic disease.

Does allergy begin in utero?

It has been recognized for centuries that allergic disease runs in families, implying a role for genetic factors in determining individual susceptibility. More recently, a range of evidence shows that many of these genetic factors, together with in utero environmental exposures, lead to the development of allergic disease through altered immune and organ development. Environmental exposures during pregnancy including diet, nutrient intake and toxin exposures can alter the epigenome and interact with inherited genetic and epigenetic risk factors to directly and indirectly influence organ development and immune programming. Understanding of these factors will be essential in identifying at-risk individuals and possible development of therapeutic interventions for the primary prevention of allergic disease. In this review, we summarize the evidence that suggests allergic disease begins in utero, together with possible mechanisms for the effect of environmental exposures during pregnancy on allergic disease risk, including epigenetics.

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.

A systematic review of associations between environmental exposures and development of asthma in children aged up to 9 years

OBJECTIVES

Childhood asthma is a complex condition where many environmental factors are implicated in causation. The aim of this study was to complete a systematic review of the literature describing associations between environmental exposures and the development of asthma in young children.

SETTING

A systematic review of the literature up to November 2013 was conducted using key words agreed by the research team. Abstracts were screened and potentially eligible papers reviewed. Papers describing associations between exposures and exacerbation of pre-existing asthma were not included. Papers were placed into the following predefined categories: secondhand smoke (SHS), inhaled chemicals, damp housing/mould, inhaled allergens, air pollution, domestic combustion, dietary exposures, respiratory virus infection and medications.

PARTICIPANTS

Children aged up to 9 years.

PRIMARY OUTCOMES

Diagnosed asthma and wheeze.

RESULTS

14,691 abstracts were identified, 207 papers reviewed and 135 included in the present review of which 15 were systematic reviews, 6 were meta-analyses and 14 were intervention studies. There was consistent evidence linking exposures to SHS, inhaled chemicals, mould, ambient air pollutants, some deficiencies in maternal diet and respiratory viruses to an increased risk for asthma (OR typically increased by 1.5-2.0). There was less consistent evidence linking exposures to pets, breast feeding and infant dietary exposures to asthma risk, and although there were consistent associations between exposures to antibiotics and paracetamol in early life, these associations might reflect reverse causation. There was good evidence that exposures to house dust mites (in isolation) was not associated with asthma risk. Evidence from observational and intervention studies suggest that interactions between exposures were important to asthma causation, where the effect size was typically 1.5-3.0.

CONCLUSIONS

There are many publications reporting associations between environmental exposures and modest changes in risk for asthma in young children, and this review highlights the complex interactions between exposures that further increase risk.

Epigenomics and allergic disease

Allergic disease development is affected by both genes and the environment, and epigenetic mechanisms are hypothesized to mediate these environmental effects. In this article, we discuss the link between the environment, DNA methylation and allergic disease, as well as questions of causality inherent to analyses of DNA methylation. From the practical side, we describe characteristics of allergic phenotypes and contrast different epidemiologic study designs used in epigenetic research. We examine methodological considerations, how best to conduct preprocessing and analysis of DNA methylation data sets, and the latest methods, technologies and discoveries in this rapidly advancing field. DNA methylation and other epigenetic marks are firmly entwined with allergic disease, a link that may hold the basis for future allergic disease diagnosis and treatment.

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.

Interaction of prenatal maternal smoking, interleukin 13 genetic variants and DNA methylation influencing airflow and airway reactivity

BACKGROUND

Asthma is characterized by airflow limitation and airway reactivity (AR). Interleukin-13 (IL-13) is involved in the pathogenesis of asthma. Two functional SNPs, rs20541 and rs1800925, of the IL-13 gene (IL13) have been frequently associated with asthma-related lung functions. However, genetic variation alone does not fully explain asthma risk. DNA-methylation (DNA-M) is an epigenetic mechanism that regulates gene expression and can be influenced by both environment and genetic variants. To explore the interplay of prenatal maternal smoking, genetic variants and DNA-M, we used a two-stage model: (1) identifying cytosine phosphate guanine (CpG) sites where DNA-M is influenced by the interaction between genetic variants and maternal smoking during pregnancy (conditional methQTL (methylation quantitative trait loci)); and (2) determining the effect of the interaction between DNA-M of CpG (from stage 1) and SNPs (modifying genetic variants; modGV) on airflow limitation and AR in 245 female participants of the Isle of Wight birth cohort. DNA-M was assessed using the Illumina Infinium HumanMethylation450 BeadChip.

FINDINGS

Six CpG sites were analyzed in stage 1. DNA-M at cg13566430 was influenced by interaction of maternal smoking during pregnancy and rs20541. In stage 2, genotype at rs1800925 interacted with DNA-M at cg13566430 significantly affecting airflow limitation (P = 0.042) and AR (P = 0.01).

CONCLUSION

Both genetic variants and environment affect DNA-M. This study supports the proposed two-stage model (methQTL and modGV) to study genetic variants, environment and DNA-M interactions in asthma-related lung function.

Clinical profile of recurrent community-acquired pneumonia in children

BACKGROUND

The aim of this case-control study was to analyse the clinical characteristics of children with recurrent community-acquired pneumonia (rCAP) affecting different lung areas (DLAs) and compare them with those of children who have never experienced CAP in order to contribute to identifying the best approach to such patients.

METHODS

The study involved 146 children with ≥2 episodes of radiographically confirmed CAP in DLA in a single year (or ≥3 episodes in any time frame) with radiographic clearing of densities between occurrences, and 145 age- and gender-matched controls enrolled in Milan, Italy, between January 2009 and December 2012. The demographic and clinical characteristics of the cases and controls were compared, and a comparison was also made between the cases with rCAP (i.e. ≤3 episodes) and those with highly recurrent CAP (hrCAP: i.e. >3 episodes).

RESULTS

Gestational age at birth (p = 0.003), birth weight (p = 0.006), respiratory distress at birth (p < 0.001), and age when starting day care attendance (p < 0.001) were significantly different between the cases and controls, and recurrent infectious wheezing (p < 0.001), chronic rhinosinusitis with post-nasal drip (p < 0.001), recurrent upper respiratory tract infections (p < 0.001), atopy/allergy (p < 0.001) and asthma (p < 0.001) were significantly more frequent. Significant risk factors for hrCAP were gastroesophageal reflux disease (GERD; p = 0.04), a history of atopy and/or allergy (p = 0.005), and a diagnosis of asthma (p = 0.0001) or middle lobe syndrome (p = 0.001). Multivariate logistic regression analysis, adjusted for age and gender, showed that all of the risk factors other than GERD and wheezing were associated with hrCAP.

CONCLUSIONS

The diagnostic approach to children with rCAP in DLAs is relatively easy in the developed world, where the severe chronic underlying diseases favouring rCAP are usually identified early, and patients with chronic underlying disease are diagnosed before the occurrence of rCAP in DLAs. When rCAP in DLAs does occur, an evaluation of the patients' history and clinical findings make it possible to limit diagnostic investigations.

Variable selection in semi-parametric models

We propose Bayesian variable selection methods in semi-parametric models in the framework of partially linear Gaussian and problit regressions. Reproducing kernels are utilized to evaluate possibly non-linear joint effect of a set of variables. Indicator variables are introduced into the reproducing kernels for the inclusion or exclusion of a variable. Different scenarios based on posterior probabilities of including a variable are proposed to select important variables. Simulations are used to demonstrate and evaluate the methods. It was found that the proposed methods can efficiently select the correct variables regardless of the feature of the effects, linear or non-linear in an unknown form. The proposed methods are applied to two real data sets to identify cytosine phosphate guanine methylation sites associated with maternal smoking and cytosine phosphate guanine sites associated with cotinine levels with creatinine levels adjusted. The selected methylation sites have the potential to advance our understanding of the underlying mechanism for the impact of smoking exposure on health outcomes, and consequently benefit medical research in disease intervention.

Breastfeeding, introduction of other foods and effects on health: a systematic literature review for the 5th Nordic Nutrition Recommendations

The present systematic literature review is part of the 5th revision of the Nordic Nutrition Recommendations. The overall aim was to review recent scientific data valid in a Nordic setting on the short- and long-term health effects of breastfeeding (duration of both any and exclusive breastfeeding) and introduction of foods other than breast milk. The initial literature search resulted in 2,011 abstracts; 416 identified as potentially relevant. Full paper review resulted in 60 quality assessed papers (6A, 48B, and 6C). A complementary search found some additional papers. The grade of evidence was classified as convincing, probable, limited-suggestive, and limited-no conclusion. The evidence was convincing of a protective dose/duration effect of breastfeeding against overweight and obesity in childhood and adolescence, overall infections, acute otitis media, and gastrointestinal and respiratory tract infections. The evidence was probable that exclusive breastfeeding for longer than 4 months is associated with slower weight gain during the second half of the first year which could be part of the reason behind the reduced risk of later overweight or obesity. There was also probable evidence that breastfeeding is a protective factor against inflammatory bowel disease, celiac disease, and diabetes (type 1 and 2), provides beneficial effects on IQ and developmental scores of children as well as a small reductive effect on blood pressure and blood cholesterol levels in adulthood. Other associations explored were limited-suggestive or inconclusive. In conclusion, convincing and probable evidence was found for benefits of breastfeeding on several outcomes. The recommendation in NNR2004 about exclusive breastfeeding for 6 months and continued partial breastfeeding thereafter can stand unchanged. The relatively low proportion of infants in the Nordic countries following this recommendation indicates that strategies that protect, support and promote breastfeeding should be enhanced, and should also recognize the benefits for long-term health.

Recurrent lower respiratory tract infections in children: a practical approach to diagnosis

Many children are affected by recurrent lower respiratory tract infections (LRTIs), but the majority of them do not suffer from serious lung or extrapulmonary disease. The challenge for clinicians is to distinguish the recurrent RTIs with self-limiting or minor problems from those with underlying disease. The aim of this review is to describe a practical approach to children with recurrent LRTIs that limits unnecessary, expensive and time-consuming investigations. The children can be divided into three groups on the basis of their personal and family history and clinical findings: 1) otherwise healthy children who do not need further investigations; 2) those with risk factors for respiratory infections for whom a wait-and-see approach can be recommended; and 3) those in whom further investigations are mandatory. However, regardless of the origin of the recurrent LRTIs, it is important to remember that prevention by means of vaccines against respiratory pathogens (i.e. type b Haemophilus influenzae, pertussis, pneumococcal and influenza vaccines) can play a key role.

Asthma and pregnancy

Asthma is probably the most common serious medical disorder that may complicate pregnancy. A third of pregnant women with asthma will experience worsening of their symptoms, a third will see improvement of their symptoms and a third will see no change. The primary goal is to maintain optimal control of asthma for maternal health and well-being as well as fetal maturation. Vital patient education should cover the use of controller medication, avoidance of asthma triggers and early treatment of asthma exacerbations. Proper asthma management should ideally be started in the preconception period. Since smoking is probably the most modifiable risk factor of asthma, pregnant woman should avoid active and passive smoking. Acute asthma exacerbation during the first trimester is associated with an increased risk of congenital malformations. Poorly controlled asthma is associated with low birth weight, preeclampsia, and preterm birth. Medications used for asthma control in the non-pregnant population are generally the same in pregnancy with a few exceptions. Inhaled corticosteroids (ICS) are the preferred controller therapy. Budesonide is the preferred ICS. Long-acting B-agonists (LABA) are the preferred add-on therapy to medium to high dose ICS. Major triggers for asthma exacerbations during pregnancy are viral infections and ICS nonadherence.

Response to infections in patients with asthma and atopic disease: an epiphenomenon or reflection of host susceptibility?

Associations between respiratory tract infections and asthma inception and exacerbations are well established. Infant respiratory syncytial virus and rhinovirus infections are known to be associated with an increased risk of asthma development, and among children with prevalent asthma, 85% of asthma exacerbations are associated with viral infections. However, the exact nature of this relationship remains unclear. Is the increase in severity of infections an epiphenomenon, meaning respiratory tract infections just appear to be more severe in patients with underlying respiratory disease, or instead a reflection of altered host susceptibility among persons with asthma and atopic disease? The main focus of this review is to summarize the available levels of evidence supporting or refuting the notion that patients with asthma or atopic disease have an altered susceptibility to selected pathogens, as well as discussing the biological mechanism or mechanisms that might explain such associations. Finally, we will outline areas in need of further research because understanding the relationships between infections and asthma has important implications for asthma prevention and treatment, including potential new pathways that might target the host immune response to select pathogens.

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.

Smoking behaviour before, during, and after pregnancy: the effect of breastfeeding

Data for this study were obtained from a population-based follow-up study in 25 Italian Local Health Units (LHUs) to evaluate pregnancy, delivery, and postpartum care in Italy. A sample of 3534 women was recruited and interviewed within a few days of their giving birth and at 3, 6, and 12 months after delivery, by trained interviewers using questionnaires. The objective of the study was to evaluate changes in smoking behaviour from one interview to the next. Of 2546 women who completed the follow-up, smoking prevalences before and during pregnancy were 21.6% and 6.7%; smoking prevalences and smoking relapse at 3, 6, and 12 months were 8.1% and 18.5%, 10.3% and 30.3%, and 10.9% and 32.3%, respectively. Smoking during and after pregnancy was more likely among women who were less educated, single, not attending antenatal classes, employed, and not breastfeeding. The results show that women who are breastfeeding smoke less than not breastfeeding women, even after controlling for other predictors (i.e.,  smoking relapse at 12 months: OR = 0.43, 95%  CI:  0.19, 0.94). A low maternal mood increases the risk of smoking relapse within 6 months of about 73%. This study also suggests that prolonged breastfeeding reduces the risk of smoking relapse and that this reduction may be persistent in time. Interventions targeting breastfeeding promotion may also indirectly support smoking cessation, even in absence of specific interventions.

Systematic review and meta-analysis investigating breast feeding and childhood wheezing illness

There is conflicting evidence concerning the relationship between breast feeding and wheezing illness. The objective of this study was to investigate whether there is any association between breast feeding and wheezing in children aged over 5 years and to discover possible sources of heterogeneity. An electronic search of MEDLINE and EMBASE databases was conducted from January 2000 to June 2010. In addition, reference lists from relevant publications were searched. Birth cohort, cross-sectional and case-control studies were included if they measured any breast feeding or exclusive breast feeding for 3 or 4 months. Wheezing illness, including asthma, was identified based on symptoms, reported diagnosis or objective criteria. Thirty-one publications were identified for meta-analysis. There was no association found between any or exclusive breast feeding and wheezing illness, although there was a high level of heterogeneity between the studies. Subgroup analysis revealed that any breast feeding slightly lowers the odds of wheeze (pooled odds ratio 0.92 [0.86, 0.98]) but slightly increases the odds of asthma defined by specific criteria (pooled odds ratio 1.10 [1.00, 1.22]). This meta-analysis does not provide evidence that breast feeding is protective against wheezing illness in children aged 5 years and over. The difference in the effects of breast feeding according to the nature of the wheezing illness highlights the importance of the heterogeneity of illness phenotypes.

Maternal and childhood asthma: risk factors, interactions, and ramifications

Asthma is emerging as a premier example of a health risk that can largely be molded by the status of the mother and the environmental conditions encountered during sensitive windows of prenatal and early childhood development. While genetic background, allergic status of parents, and predisposition for atopy and inflammation play a role, early-life environmental conditions can completely alter the course of immune and respiratory system development. Environmentally induced alterations that (1) maintain the Th2 bias seen during gestation, (2) block the maturation of innate immune cells and (3) create inflammatory dysfunction in the infant provide the foundation for childhood asthma. No single risk factor can fully explain the increased prevalence of asthma in recent decades but it is assumed that the rapid increase is due to environmental and/or epigenetic changes. Well-established and suspected environmental risk factors cover all categories of early life interactions from diet, exposure to environmental contaminants and drugs, maternal and neonatal infections, hygiene, timing of vaccinations and even the mode of birth delivery. Because asthma is connected to the risk of several comorbid chronic conditions, the benefit of asthma risk reduction and prevention is greater than initially may be apparent. This review discusses strategies to optimize preventative and therapeutic options across life stages.

Identifying patterns of immune-related disease: use in disease prevention and management

BACKGROUND

Childhood susceptibility to diseases linked with immune dysfunction affects over a quarter of the pediatric population in some countries. While this alone is a significant health issue, the actual impact of immune-related diseases extends over a lifetime and involves additional secondary conditions. Some comorbidities are well known (e.g., allergic rhinitis and asthma). However, no systematic approach has been used to identify life-long patterns of immune-based disease where the primary condition arises in childhood. Such information is useful for both disease prevention and treatment approaches.

DATA SOURCES

Recent primary research papers as well as review articles were obtained from PubMed, Chem Abstracts, Biosis and from the personal files of the authors. Search words used were: the diseases and conditions shown Figs. 1 and 2 in conjunction with comorbid, comorbidities, pediatric, childhood, adult, immune, immune dysfunction, allergy, autoimmune, inflammatory, infectious, health risks, environment, risk factors.

RESULTS

Childhood diseases such as asthma, type-1 diabetes, inflammatory bowel disease, respiratory infections /rhinitis, recurrent otitis media, pediatric celiac, juvenile arthritis and Kawasaki disease are examples of significant childhood health problems where immune dysfunction plays a significant role. Each of these pediatric diseases is associated with increased risk of several secondary conditions, many of which appear only later in life. To illustrate, four prototypes of immune-related disease patterns (i.e., allergy, autoimmunity, inflammation and infectious disease) are shown as tools for: 1) enhanced disease prevention; 2) improved management of immune-based pediatric diseases; and 3) better recognition of underlying pediatric immune dysfunction.

CONCLUSIONS

Identification of immune-related disease patterns beginning in childhood provides the framework for examining the underlying immune dysfunctions that can contribute to additional diseases in later life. Many pediatric diseases associated with dysfunctional immune responses have been linked with an elevated risk of other diseases or conditions as the child ages. Diseases within a pattern may be interlinked based on underlying immune dysfunctions and/or current therapeutic approaches for managing the entryway diseases. It may be beneficial to consider treatment options for the earliest presenting diseases that will concomitantly reduce the risk of immune-linked secondary conditions. Additionally, improved disease prevention is possible with more relevant and age-specific immune safety testing.

Asthma and pregnancy: emerging evidence of epigenetic interactions in utero

PURPOSE OF REVIEW

Pregnancy is arguably the most critical period of developmental programming. Here, we particularly focus on the emerging paradigm that disease propensity is epigenetically determined by maternal exposures that have the capacity to activate or silence fetal genes through alterations in DNA and histone methylation, histone acetylation, and chromatin structure.

RECENT FINDINGS

The most notable recent candidate to emerge in this role has been dietary folate, a methyl donor clearly associated with changes in gene expression and disease susceptibility through gene hypermethylation. Animal studies also provide the first evidence that the allergy protective effects of microbial exposure in pregnancy may be mediated by changes in methylation of Th1 genes of the offspring. There is also emerging evidence that perinatal differences in immune function of allergy-prone newborns extend beyond previously recognized differences in effector T cell (Th1/Th2) function, to also include differences in neonatal regulatory T cell (Treg) and Th17 function, and moreover, that these pathways are also epigenetically regulated.

SUMMARY

New studies reinforce the importance of in-utero exposures (including dietary nutrients, microbial products, cigarette smoking, and certain maternal mediations) in fetal immune development and in programming the susceptibility to asthma and allergic disease.

Breastfeeding is an essential complement to vaccination

AIM

This article explores the role of breastfeeding in different aspects of vaccination in the first 6 months when infants are still developing: (1) pain management; (2) immunomodulation of infants' vaccine responses; (3) metabolism of thimerosal.

METHODS

Major databases were searched for studies that addressed outcomes of related issues.

RESULTS

Studies reveal that breastfeeding can: (1) help mothers and infants to cope with the stressful situations that accompany parenteral vaccines; (2) improve response to vaccines in the still maturing immunologic and enterohepatic systems of infants; (3) influence physiologic parameters that can change metabolism of ethylmercury derived from some vaccines.

CONCLUSION

Health promotion that supports vaccinations should also emphasize early initiation and maintenance of exclusive breastfeeding up until 6 months for maximum protection of the infants with a possible beneficial effect on the vaccine response. Paediatric professionals should inform mothers of the proven benefits of breastfeeding and its importance in complementing vaccination and lowering stress and the risk of untoward reactions on susceptible infants.